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    Subject[RFC][PATCH 1/3] radix priority search tree - objrmap complexity fix

    This patch is an attempt at fixing the much discussed search complexity issues
    in objrmap design. The key idea is to replace the i_mmap{_shared} list with a
    new tree data structure.

    The radix priority search tree (prio_tree) first proposed by Edward M. McCreight
    is used as the new data structure. A prio_tree is indexed by two indices which
    we call radix_index and heap_index. The tree is a simple binary radix tree on
    the radix_index with an additional heap tree like property that a parent node's
    heap_index is always greater than or equal to the heap_indices of its children.

    An interesting property of the prio_tree is that they are useful to store and
    query intervals, for example, a file-mapped vm_area_struct can be considered
    as an interval of file pages. If we store all vmas that map a file in a
    prio_tree, then we can execute a stabbing query, i.e., choosing a set of vmas
    that a map a single file page or a set of contiguous file pages, in O(log n + m)
    time where "log n" indicates the height of the tree (maximum 64 in a 32 bit
    machine) and "m" represents the number of vmas that map the page(s).

    The test results below show that the prio_tree effectively solves the objrmap
    i_mmap{_shared} search complexity problems. The tests were done on a PII
    200 MHz machine with 256MB RAM using UP kernels.

    This patch is for 2.6.5-rc2. The patch boots and works both on SMP and UP.
    Further testing will help. If you like broken-out patches please check:

    http://www-personal.engin.umich.edu/~vrajesh/~vrajesh/linux/prio_tree/

    Some Results:

    Kernel compile - 2.6.2 defconfig - make
    2.6.5-rc2 3313.97 user 261.08 system 1:00:11 elapsed 98% CPU
    rc2+prio+objrmap 3315.30 user 258.59 system 1:00:14 elapsed 98% CPU
    rc2+objrmap 3316.41 user 257.77 system 1:00:10 elapsed 98% CPU

    rmap-test 1 - ./rmap-test -l -i 10 -n 100 -s 600 -t 100 foo
    2.6.5-rc2 67.57 user 277.14 system 0:13:12 elapsed 43% CPU
    rc2+prio+objrmap 71.99 user 203.90 system 0:13:30 elapsed 34% CPU
    rc2+objrmap 70.45 user 19834.38 system 7:28:04 elapsed 74% CPU
    -I killed the process after 7 hours. System was responsive afer
    killing the process. Compared to previous results, the program
    should not lock or take so long. Maybe it is due to this problem
    identified by Andrea:
    http://marc.theaimsgroup.com/?l=linux-kernel&m=107966438414248

    Andrea says the system may hang, however, in this case system
    does not hang.

    rmap-test 2 - ./rmap-test -vv -V 2 -r -i 1 -n 100 -s 600 -t 100 foo
    2.6.5-rc2 0.58 user 212.50 system 0: 7:32 elapsed 47% CPU
    rc2+prio+objrmap 0.63 user 101.77 system 0: 4:44 elapsed 36% CPU
    rc2+objrmap 0.60 user 605.97 system 0:14:35 elapsed 69% CPU


    rmap-test 3 - ./rmap-test -v -l -i 10 -n 10000 -s 7 -t 1 foo
    2.6.5-rc2 1.07 user 31.08 system 0:16:06 elapsed 3% CPU
    rc2+prio+objrmap 1.03 user 31.41 system 0:16:38 elapsed 3% CPU
    rc2+objrmap 0.53 user 1588.40 system 2:25:27 elapsed 18% CPU
    -I killed the process after around 2 1/2 hours.
    System was responsive afer killing the process.

    test-mmap2 H M Sec.
    2.6.5-rc2 0.00 user 0.34 system 0:0:01.55 elapsed 22% CPU
    rc2+prio+objramp 0.00 user 0.35 system 0:0:01.49 elapsed 23% CPU
    rc2+objrmap - didn't try - already known to lock the system


    test-mmap3 H M Sec.
    2.6.5-rc2 0.06 user 3.38 system 0:0:14.62 elapsed 23% CPU
    rc2+prio+objrmap 0.09 user 3.65 system 0:0:13.99 elapsed 26% CPU
    rc2+objrmap - didn't try - known to lock the system


    Lowlights of the patch:

    * Adds a new tree data structure (around 500 lines of code + bugs?)
    - code seems reasonably stable. More testing will help a lot.

    * Breaks compilation of hugetlbfs, xfs, and few archs.
    - easily fixable.

    * Adds 2 extra pointers to vm_area_struct
    - both of these pointers can be removed later.

    - Plan:

    * Shove vm_list_head into vm_private_data.

    * I need a single bit protected by i_shared_sem to
    mark prio_tree nodes. When I get convinced that I can use
    the least significant bit of the vm_list_head for marking
    nodes (vm_area_struct alignment?), I plan to remove the parent
    field and use percpu array in prio_tree_insert and
    prio_tree_remove. In invalidate_mmap_range_list, we can try to
    allocate an array from slab (helps to avoid high latency in
    truncate), if we fail, we can fall back to percpu array.

    Useful Links:

    [1] Andrew Morton's rmap-test.c
    http://marc.theaimsgroup.com/?l=linux-kernel&m=104954444204356

    [2] Ingo's test-mmap2.c
    http://marc.theaimsgroup.com/?l=linux-kernel&m=107883030601436

    [3] Ingo's test-mmap3.c
    http://marc.theaimsgroup.com/?l=linux-kernel&m=107886160312419



    fs/exec.c | 2
    fs/inode.c | 4
    fs/locks.c | 6
    fs/proc/task_mmu.c | 2
    include/linux/fs.h | 5
    include/linux/mm.h | 168 +++++++++++++
    include/linux/prio_tree.h | 78 ++++++
    init/main.c | 2
    kernel/fork.c | 4
    mm/Makefile | 3
    mm/filemap.c | 2
    mm/memory.c | 15 -
    mm/mmap.c | 66 +++--
    mm/mremap.c | 21 +
    mm/prio_tree.c | 574 ++++++++++++++++++++++++++++++++++++++++++++++
    mm/shmem.c | 2
    mm/swap_state.c | 4
    mm/vmscan.c | 4
    18 files changed, 910 insertions(+), 52 deletions(-)

    diff -puN fs/exec.c~prio_tree_core fs/exec.c
    --- mmlinux-2.6/fs/exec.c~prio_tree_core 2004-03-21 16:25:01.000000000 -0500
    +++ mmlinux-2.6-jaya/fs/exec.c 2004-03-21 16:25:34.000000000 -0500
    @@ -430,7 +430,7 @@ int setup_arg_pages(struct linux_binprm
    mpnt->vm_ops = NULL;
    mpnt->vm_pgoff = 0;
    mpnt->vm_file = NULL;
    - INIT_LIST_HEAD(&mpnt->shared);
    + INIT_VMA_SHARED(mpnt);
    mpnt->vm_private_data = (void *) 0;
    insert_vm_struct(mm, mpnt);
    mm->total_vm = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
    diff -puN fs/inode.c~prio_tree_core fs/inode.c
    --- mmlinux-2.6/fs/inode.c~prio_tree_core 2004-03-21 16:25:01.000000000 -0500
    +++ mmlinux-2.6-jaya/fs/inode.c 2004-03-21 16:25:01.000000000 -0500
    @@ -189,8 +189,8 @@ void inode_init_once(struct inode *inode
    atomic_set(&inode->i_data.truncate_count, 0);
    INIT_LIST_HEAD(&inode->i_data.private_list);
    spin_lock_init(&inode->i_data.private_lock);
    - INIT_LIST_HEAD(&inode->i_data.i_mmap);
    - INIT_LIST_HEAD(&inode->i_data.i_mmap_shared);
    + INIT_PRIO_TREE_ROOT(&inode->i_data.i_mmap);
    + INIT_PRIO_TREE_ROOT(&inode->i_data.i_mmap_shared);
    spin_lock_init(&inode->i_lock);
    i_size_ordered_init(inode);
    }
    diff -puN fs/locks.c~prio_tree_core fs/locks.c
    --- mmlinux-2.6/fs/locks.c~prio_tree_core 2004-03-21 16:25:01.000000000 -0500
    +++ mmlinux-2.6-jaya/fs/locks.c 2004-03-21 16:25:01.000000000 -0500
    @@ -1455,8 +1455,7 @@ int fcntl_setlk(struct file *filp, unsig
    if (IS_MANDLOCK(inode) &&
    (inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID) {
    struct address_space *mapping = filp->f_mapping;
    -
    - if (!list_empty(&mapping->i_mmap_shared)) {
    + if (!prio_tree_empty(&mapping->i_mmap_shared)) {
    error = -EAGAIN;
    goto out;
    }
    @@ -1593,8 +1592,7 @@ int fcntl_setlk64(struct file *filp, uns
    if (IS_MANDLOCK(inode) &&
    (inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID) {
    struct address_space *mapping = filp->f_mapping;
    -
    - if (!list_empty(&mapping->i_mmap_shared)) {
    + if (!prio_tree_empty(&mapping->i_mmap_shared)) {
    error = -EAGAIN;
    goto out;
    }
    diff -puN fs/proc/task_mmu.c~prio_tree_core fs/proc/task_mmu.c
    --- mmlinux-2.6/fs/proc/task_mmu.c~prio_tree_core 2004-03-21 16:25:01.000000000 -0500
    +++ mmlinux-2.6-jaya/fs/proc/task_mmu.c 2004-03-21 16:25:01.000000000 -0500
    @@ -65,7 +65,7 @@ int task_statm(struct mm_struct *mm, int
    *shared += pages;
    continue;
    }
    - if (vma->vm_flags & VM_SHARED || !list_empty(&vma->shared))
    + if (vma->vm_flags & VM_SHARED || !vma_shared_empty(vma))
    *shared += pages;
    if (vma->vm_flags & VM_EXECUTABLE)
    *text += pages;
    diff -puN include/linux/fs.h~prio_tree_core include/linux/fs.h
    --- mmlinux-2.6/include/linux/fs.h~prio_tree_core 2004-03-21 16:25:01.000000000 -0500
    +++ mmlinux-2.6-jaya/include/linux/fs.h 2004-03-21 16:25:01.000000000 -0500
    @@ -18,6 +18,7 @@
    #include <linux/stat.h>
    #include <linux/cache.h>
    #include <linux/radix-tree.h>
    +#include <linux/prio_tree.h>
    #include <linux/kobject.h>
    #include <asm/atomic.h>

    @@ -329,8 +330,8 @@ struct address_space {
    struct list_head io_pages; /* being prepared for I/O */
    unsigned long nrpages; /* number of total pages */
    struct address_space_operations *a_ops; /* methods */
    - struct list_head i_mmap; /* list of private mappings */
    - struct list_head i_mmap_shared; /* list of shared mappings */
    + struct prio_tree_root i_mmap; /* tree of private mappings */
    + struct prio_tree_root i_mmap_shared; /* tree of shared mappings */
    struct semaphore i_shared_sem; /* protect both above lists */
    atomic_t truncate_count; /* Cover race condition with truncate */
    unsigned long dirtied_when; /* jiffies of first page dirtying */
    diff -puN include/linux/mm.h~prio_tree_core include/linux/mm.h
    --- mmlinux-2.6/include/linux/mm.h~prio_tree_core 2004-03-21 16:25:01.000000000 -0500
    +++ mmlinux-2.6-jaya/include/linux/mm.h 2004-03-21 16:25:34.000000000 -0500
    @@ -11,6 +11,7 @@
    #include <linux/list.h>
    #include <linux/mmzone.h>
    #include <linux/rbtree.h>
    +#include <linux/prio_tree.h>
    #include <linux/fs.h>

    #ifndef CONFIG_DISCONTIGMEM /* Don't use mapnrs, do it properly */
    @@ -67,8 +68,29 @@ struct vm_area_struct {
    * one of the address_space->i_mmap{,shared} lists,
    * for shm areas, the list of attaches, otherwise unused.
    */
    - struct list_head shared;
    + union {
    + struct {
    + struct list_head list;
    + void *parent;
    + } vm_set;
    +
    + struct prio_tree_node prio_tree_node;
    +
    + struct {
    + void *first;
    + void *second;
    + void *parent;
    + } both;
    + } shared;

    + /*
    + * shared.vm_set : list of vmas that map exactly the same set of pages
    + * vm_set_head : head of the vm_set list
    + *
    + * TODO: try to shove the following field into vm_private_data ??
    + */
    + struct vm_area_struct *vm_set_head;
    +
    /* Function pointers to deal with this struct. */
    struct vm_operations_struct * vm_ops;

    @@ -129,6 +151,150 @@ struct vm_area_struct {
    #define VM_RandomReadHint(v) ((v)->vm_flags & VM_RAND_READ)

    /*
    + * The following macros are used for implementing prio_tree for i_mmap{_shared}
    + */
    +
    +#define RADIX_INDEX(vma) ((vma)->vm_pgoff)
    +#define VMA_SIZE(vma) (((vma)->vm_end - (vma)->vm_start) >> PAGE_SHIFT)
    +/* avoid overflow */
    +#define HEAP_INDEX(vma) ((vma)->vm_pgoff + (VMA_SIZE(vma) - 1))
    +
    +#define GET_INDEX_VMA(vma, radix, heap) \
    +do { \
    + radix = RADIX_INDEX(vma); \
    + heap = HEAP_INDEX(vma); \
    +} while (0)
    +
    +#define GET_INDEX(node, radix, heap) \
    +do { \
    + struct vm_area_struct *__tmp = \
    + prio_tree_entry(node, struct vm_area_struct, shared.prio_tree_node);\
    + GET_INDEX_VMA(__tmp, radix, heap); \
    +} while (0)
    +
    +#define INIT_VMA_SHARED_LIST(vma) \
    +do { \
    + INIT_LIST_HEAD(&(vma)->shared.vm_set.list); \
    + (vma)->shared.vm_set.parent = NULL; \
    + (vma)->vm_set_head = NULL; \
    +} while (0)
    +
    +#define INIT_VMA_SHARED(vma) \
    +do { \
    + (vma)->shared.both.first = NULL; \
    + (vma)->shared.both.second = NULL; \
    + (vma)->shared.both.parent = NULL; \
    + (vma)->vm_set_head = NULL; \
    +} while (0)
    +
    +extern void __vma_prio_tree_insert(struct prio_tree_root *,
    + struct vm_area_struct *);
    +
    +extern void __vma_prio_tree_remove(struct prio_tree_root *,
    + struct vm_area_struct *);
    +
    +static inline int vma_shared_empty(struct vm_area_struct *vma)
    +{
    + return vma->shared.both.first == NULL;
    +}
    +
    +/*
    + * Helps to add a new vma that maps the same (identical) set of pages as the
    + * old vma to an i_mmap tree.
    + */
    +static inline void __vma_prio_tree_add(struct vm_area_struct *vma,
    + struct vm_area_struct *old)
    +{
    + INIT_VMA_SHARED_LIST(vma);
    +
    + /* Leave these BUG_ONs till prio_tree patch stabilizes */
    + BUG_ON(RADIX_INDEX(vma) != RADIX_INDEX(old));
    + BUG_ON(HEAP_INDEX(vma) != HEAP_INDEX(old));
    +
    + if (old->shared.both.parent) {
    + if (old->vm_set_head) {
    + list_add_tail(&vma->shared.vm_set.list,
    + &old->vm_set_head->shared.vm_set.list);
    + return;
    + }
    + else {
    + old->vm_set_head = vma;
    + vma->vm_set_head = old;
    + }
    + }
    + else
    + list_add(&vma->shared.vm_set.list, &old->shared.vm_set.list);
    +}
    +
    +/*
    + * We cannot modify vm_start, vm_end, vm_pgoff fields of a vma that has been
    + * already present in an i_mmap{_shared} tree without modifying the tree. The
    + * following helper function should be used when such modifications are
    + * necessary. We should hold the mapping's i_shared_sem.
    + *
    + * This function can be (micro)optimized for some special cases (maybe later).
    + */
    +static inline void __vma_modify(struct prio_tree_root *root,
    + struct vm_area_struct *vma, unsigned long start, unsigned long end,
    + unsigned long pgoff)
    +{
    + if (root)
    + __vma_prio_tree_remove(root, vma);
    + vma->vm_start = start;
    + vma->vm_end = end;
    + vma->vm_pgoff = pgoff;
    + if (root)
    + __vma_prio_tree_insert(root, vma);
    +}
    +
    +/*
    + * Helper functions to enumerate vmas that map a given file page or a set of
    + * contiguous file pages. The functions return vmas that at least map a single
    + * page in the given range of contiguous file pages.
    + */
    +static inline struct vm_area_struct *__vma_prio_tree_first(
    + struct prio_tree_root *root, struct prio_tree_iter *iter,
    + unsigned long begin, unsigned long end)
    +{
    + struct prio_tree_node *ptr;
    +
    + ptr = prio_tree_first(root, iter, begin, end);
    +
    + if (ptr)
    + return prio_tree_entry(ptr, struct vm_area_struct,
    + shared.prio_tree_node);
    + else
    + return NULL;
    +}
    +
    +static inline struct vm_area_struct *__vma_prio_tree_next(
    + struct vm_area_struct *vma, struct prio_tree_root *root,
    + struct prio_tree_iter *iter, unsigned long begin, unsigned long end)
    +{
    + struct prio_tree_node *ptr;
    + struct vm_area_struct *next;
    +
    + if (vma->shared.both.parent) {
    + if (vma->vm_set_head)
    + return vma->vm_set_head;
    + }
    + else {
    + next = list_entry(vma->shared.vm_set.list.next,
    + struct vm_area_struct, shared.vm_set.list);
    + if (!(next->vm_set_head))
    + return next;
    + }
    +
    + ptr = prio_tree_next(root, iter, begin, end);
    +
    + if (ptr)
    + return prio_tree_entry(ptr, struct vm_area_struct,
    + shared.prio_tree_node);
    + else
    + return NULL;
    +}
    +
    +/*
    * mapping from the currently active vm_flags protection bits (the
    * low four bits) to a page protection mask..
    */
    diff -puN /dev/null include/linux/prio_tree.h
    --- /dev/null 2003-01-30 05:24:37.000000000 -0500
    +++ mmlinux-2.6-jaya/include/linux/prio_tree.h 2004-03-21 16:25:01.000000000 -0500
    @@ -0,0 +1,78 @@
    +#ifndef _LINUX_PRIO_TREE_H
    +#define _LINUX_PRIO_TREE_H
    +
    +struct prio_tree_node {
    + struct prio_tree_node *left;
    + struct prio_tree_node *right;
    + struct prio_tree_node *parent;
    +};
    +
    +struct prio_tree_root {
    + struct prio_tree_node *prio_tree_node;
    + unsigned int index_bits;
    +};
    +
    +struct prio_tree_iter {
    + struct prio_tree_node *cur;
    + unsigned long mask;
    + unsigned long value;
    + int size_level;
    +};
    +
    +#define PRIO_TREE_ROOT (struct prio_tree_root) {NULL, 1}
    +
    +#define PRIO_TREE_ROOT_INIT {NULL, 1}
    +
    +#define INIT_PRIO_TREE_ROOT(ptr) \
    +do { \
    + (ptr)->prio_tree_node = NULL; \
    + (ptr)->index_bits = 1; \
    +} while (0)
    +
    +#define PRIO_TREE_NODE_INIT(name) {&(name), &(name), &(name)}
    +
    +#define PRIO_TREE_NODE(name) \
    + struct prio_tree_node name = PRIO_TREE_NODE_INIT(name)
    +
    +#define INIT_PRIO_TREE_NODE(ptr) \
    +do { \
    + (ptr)->left = (ptr)->right = (ptr)->parent = (ptr); \
    +} while (0)
    +
    +#define prio_tree_entry(ptr, type, member) \
    + ((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))
    +
    +#define PRIO_TREE_ITER (struct prio_tree_iter) {NULL, 0UL, 0UL, 0}
    +
    +static inline int prio_tree_empty(const struct prio_tree_root *root)
    +{
    + return root->prio_tree_node == NULL;
    +}
    +
    +static inline int prio_tree_root(const struct prio_tree_node *node)
    +{
    + return node->parent == node;
    +}
    +
    +static inline int prio_tree_left_empty(const struct prio_tree_node *node)
    +{
    + return node->left == node;
    +}
    +
    +static inline int prio_tree_right_empty(const struct prio_tree_node *node)
    +{
    + return node->right == node;
    +}
    +
    +extern struct prio_tree_node *prio_tree_insert(struct prio_tree_root *,
    + struct prio_tree_node *);
    +
    +extern void prio_tree_remove(struct prio_tree_root *, struct prio_tree_node *);
    +
    +extern struct prio_tree_node *prio_tree_first(struct prio_tree_root *,
    + struct prio_tree_iter *, unsigned long, unsigned long);
    +
    +extern struct prio_tree_node *prio_tree_next(struct prio_tree_root *,
    + struct prio_tree_iter *, unsigned long, unsigned long);
    +
    +#endif
    diff -puN init/main.c~prio_tree_core init/main.c
    --- mmlinux-2.6/init/main.c~prio_tree_core 2004-03-21 16:25:01.000000000 -0500
    +++ mmlinux-2.6-jaya/init/main.c 2004-03-21 16:25:01.000000000 -0500
    @@ -86,6 +86,7 @@ extern void pidhash_init(void);
    extern void pidmap_init(void);
    extern void pte_chain_init(void);
    extern void radix_tree_init(void);
    +extern void prio_tree_init(void);
    extern void free_initmem(void);
    extern void populate_rootfs(void);
    extern void driver_init(void);
    @@ -460,6 +461,7 @@ asmlinkage void __init start_kernel(void
    calibrate_delay();
    pidmap_init();
    pgtable_cache_init();
    + prio_tree_init();
    pte_chain_init();
    #ifdef CONFIG_X86
    if (efi_enabled)
    diff -puN kernel/fork.c~prio_tree_core kernel/fork.c
    --- mmlinux-2.6/kernel/fork.c~prio_tree_core 2004-03-21 16:25:01.000000000 -0500
    +++ mmlinux-2.6-jaya/kernel/fork.c 2004-03-21 16:25:01.000000000 -0500
    @@ -313,7 +313,7 @@ static inline int dup_mmap(struct mm_str
    tmp->vm_mm = mm;
    tmp->vm_next = NULL;
    file = tmp->vm_file;
    - INIT_LIST_HEAD(&tmp->shared);
    + INIT_VMA_SHARED(tmp);
    if (file) {
    struct inode *inode = file->f_dentry->d_inode;
    get_file(file);
    @@ -322,7 +322,7 @@ static inline int dup_mmap(struct mm_str

    /* insert tmp into the share list, just after mpnt */
    down(&file->f_mapping->i_shared_sem);
    - list_add_tail(&tmp->shared, &mpnt->shared);
    + __vma_prio_tree_add(tmp, mpnt);
    up(&file->f_mapping->i_shared_sem);
    }

    diff -puN mm/filemap.c~prio_tree_core mm/filemap.c
    --- mmlinux-2.6/mm/filemap.c~prio_tree_core 2004-03-21 16:25:01.000000000 -0500
    +++ mmlinux-2.6-jaya/mm/filemap.c 2004-03-21 16:25:01.000000000 -0500
    @@ -630,7 +630,7 @@ page_ok:
    * virtual addresses, take care about potential aliasing
    * before reading the page on the kernel side.
    */
    - if (!list_empty(&mapping->i_mmap_shared))
    + if (!prio_tree_empty(&mapping->i_mmap_shared))
    flush_dcache_page(page);

    /*
    diff -puN mm/Makefile~prio_tree_core mm/Makefile
    --- mmlinux-2.6/mm/Makefile~prio_tree_core 2004-03-21 16:25:01.000000000 -0500
    +++ mmlinux-2.6-jaya/mm/Makefile 2004-03-21 16:25:01.000000000 -0500
    @@ -9,6 +9,7 @@ mmu-$(CONFIG_MMU) := fremap.o highmem.o

    obj-y := bootmem.o filemap.o mempool.o oom_kill.o fadvise.o \
    page_alloc.o page-writeback.o pdflush.o readahead.o \
    - slab.o swap.o truncate.o vmscan.o $(mmu-y)
    + slab.o swap.o truncate.o vmscan.o prio_tree.o \
    + $(mmu-y)

    obj-$(CONFIG_SWAP) += page_io.o swap_state.o swapfile.o
    diff -puN mm/memory.c~prio_tree_core mm/memory.c
    --- mmlinux-2.6/mm/memory.c~prio_tree_core 2004-03-21 16:25:01.000000000 -0500
    +++ mmlinux-2.6-jaya/mm/memory.c 2004-03-21 16:25:34.000000000 -0500
    @@ -1097,11 +1097,11 @@ no_pte_chain:
    * An hlen of zero blows away the entire portion file after hba.
    */
    static void
    -invalidate_mmap_range_list(struct list_head *head,
    +invalidate_mmap_range_list(struct prio_tree_root *root,
    unsigned long const hba,
    unsigned long const hlen)
    {
    - struct list_head *curr;
    + struct prio_tree_iter iter;
    unsigned long hea; /* last page of hole. */
    unsigned long vba;
    unsigned long vea; /* last page of corresponding uva hole. */
    @@ -1112,17 +1112,16 @@ invalidate_mmap_range_list(struct list_h
    hea = hba + hlen - 1; /* avoid overflow. */
    if (hea < hba)
    hea = ULONG_MAX;
    - list_for_each(curr, head) {
    - vp = list_entry(curr, struct vm_area_struct, shared);
    + vp = __vma_prio_tree_first(root, &iter, hba, hea);
    + while(vp) {
    vba = vp->vm_pgoff;
    vea = vba + ((vp->vm_end - vp->vm_start) >> PAGE_SHIFT) - 1;
    - if (hea < vba || vea < hba)
    - continue; /* Mapping disjoint from hole. */
    zba = (hba <= vba) ? vba : hba;
    zea = (vea <= hea) ? vea : hea;
    zap_page_range(vp,
    ((zba - vba) << PAGE_SHIFT) + vp->vm_start,
    (zea - zba + 1) << PAGE_SHIFT);
    + vp = __vma_prio_tree_next(vp, root, &iter, hba, hea);
    }
    }

    @@ -1157,9 +1156,9 @@ void invalidate_mmap_range(struct addres
    down(&mapping->i_shared_sem);
    /* Protect against page fault */
    atomic_inc(&mapping->truncate_count);
    - if (unlikely(!list_empty(&mapping->i_mmap)))
    + if (unlikely(!prio_tree_empty(&mapping->i_mmap)))
    invalidate_mmap_range_list(&mapping->i_mmap, hba, hlen);
    - if (unlikely(!list_empty(&mapping->i_mmap_shared)))
    + if (unlikely(!prio_tree_empty(&mapping->i_mmap_shared)))
    invalidate_mmap_range_list(&mapping->i_mmap_shared, hba, hlen);
    up(&mapping->i_shared_sem);
    }
    diff -puN mm/mmap.c~prio_tree_core mm/mmap.c
    --- mmlinux-2.6/mm/mmap.c~prio_tree_core 2004-03-21 16:25:01.000000000 -0500
    +++ mmlinux-2.6-jaya/mm/mmap.c 2004-03-21 16:25:01.000000000 -0500
    @@ -64,12 +64,16 @@ EXPORT_SYMBOL(vm_committed_space);
    * Requires inode->i_mapping->i_shared_sem
    */
    static inline void
    -__remove_shared_vm_struct(struct vm_area_struct *vma, struct inode *inode)
    +__remove_shared_vm_struct(struct vm_area_struct *vma, struct inode *inode,
    + struct address_space *mapping)
    {
    if (inode) {
    if (vma->vm_flags & VM_DENYWRITE)
    atomic_inc(&inode->i_writecount);
    - list_del_init(&vma->shared);
    + if (vma->vm_flags & VM_SHARED)
    + __vma_prio_tree_remove(&mapping->i_mmap_shared, vma);
    + else
    + __vma_prio_tree_remove(&mapping->i_mmap, vma);
    }
    }

    @@ -83,7 +87,8 @@ static void remove_shared_vm_struct(stru
    if (file) {
    struct address_space *mapping = file->f_mapping;
    down(&mapping->i_shared_sem);
    - __remove_shared_vm_struct(vma, file->f_dentry->d_inode);
    + __remove_shared_vm_struct(vma, file->f_dentry->d_inode,
    + mapping);
    up(&mapping->i_shared_sem);
    }
    }
    @@ -257,10 +262,10 @@ static inline void __vma_link_file(struc
    if (vma->vm_flags & VM_DENYWRITE)
    atomic_dec(&file->f_dentry->d_inode->i_writecount);

    - if (vma->vm_flags & VM_SHARED)
    - list_add_tail(&vma->shared, &mapping->i_mmap_shared);
    - else
    - list_add_tail(&vma->shared, &mapping->i_mmap);
    + if (vma->vm_flags & VM_SHARED)
    + __vma_prio_tree_insert(&mapping->i_mmap_shared, vma);
    + else
    + __vma_prio_tree_insert(&mapping->i_mmap, vma);
    }
    }

    @@ -390,7 +395,9 @@ static int vma_merge(struct mm_struct *m
    {
    spinlock_t *lock = &mm->page_table_lock;
    struct inode *inode = file ? file->f_dentry->d_inode : NULL;
    + struct address_space *mapping = file ? file->f_mapping : NULL;
    struct semaphore *i_shared_sem;
    + struct prio_tree_root *root = NULL;

    /*
    * We later require that vma->vm_flags == vm_flags, so this tests
    @@ -401,6 +408,13 @@ static int vma_merge(struct mm_struct *m

    i_shared_sem = file ? &file->f_mapping->i_shared_sem : NULL;

    + if (mapping) {
    + if (vm_flags & VM_SHARED)
    + root = &mapping->i_mmap_shared;
    + else
    + root = &mapping->i_mmap;
    + }
    +
    if (!prev) {
    prev = rb_entry(rb_parent, struct vm_area_struct, vm_rb);
    goto merge_next;
    @@ -421,18 +435,18 @@ static int vma_merge(struct mm_struct *m
    need_up = 1;
    }
    spin_lock(lock);
    - prev->vm_end = end;

    /*
    * OK, it did. Can we now merge in the successor as well?
    */
    next = prev->vm_next;
    - if (next && prev->vm_end == next->vm_start &&
    + if (next && end == next->vm_start &&
    can_vma_merge_before(next, vm_flags, file,
    pgoff, (end - addr) >> PAGE_SHIFT)) {
    - prev->vm_end = next->vm_end;
    + __vma_modify(root, prev, prev->vm_start,
    + next->vm_end, prev->vm_pgoff);
    __vma_unlink(mm, next, prev);
    - __remove_shared_vm_struct(next, inode);
    + __remove_shared_vm_struct(next, inode, mapping);
    spin_unlock(lock);
    if (need_up)
    up(i_shared_sem);
    @@ -443,6 +457,7 @@ static int vma_merge(struct mm_struct *m
    kmem_cache_free(vm_area_cachep, next);
    return 1;
    }
    + __vma_modify(root, prev, prev->vm_start, end, prev->vm_pgoff);
    spin_unlock(lock);
    if (need_up)
    up(i_shared_sem);
    @@ -462,8 +477,8 @@ static int vma_merge(struct mm_struct *m
    if (file)
    down(i_shared_sem);
    spin_lock(lock);
    - prev->vm_start = addr;
    - prev->vm_pgoff -= (end - addr) >> PAGE_SHIFT;
    + __vma_modify(root, prev, addr, prev->vm_end,
    + prev->vm_pgoff - ((end - addr) >> PAGE_SHIFT));
    spin_unlock(lock);
    if (file)
    up(i_shared_sem);
    @@ -649,7 +664,7 @@ munmap_back:
    vma->vm_file = NULL;
    vma->vm_private_data = NULL;
    vma->vm_next = NULL;
    - INIT_LIST_HEAD(&vma->shared);
    + INIT_VMA_SHARED(vma);

    if (file) {
    error = -EINVAL;
    @@ -1196,6 +1211,7 @@ int split_vma(struct mm_struct * mm, str
    {
    struct vm_area_struct *new;
    struct address_space *mapping = NULL;
    + struct prio_tree_root *root = NULL;

    if (mm->map_count >= MAX_MAP_COUNT)
    return -ENOMEM;
    @@ -1207,7 +1223,7 @@ int split_vma(struct mm_struct * mm, str
    /* most fields are the same, copy all, and then fixup */
    *new = *vma;

    - INIT_LIST_HEAD(&new->shared);
    + INIT_VMA_SHARED(new);

    if (new_below)
    new->vm_end = addr;
    @@ -1222,18 +1238,24 @@ int split_vma(struct mm_struct * mm, str
    if (new->vm_ops && new->vm_ops->open)
    new->vm_ops->open(new);

    - if (vma->vm_file)
    + if (vma->vm_file) {
    mapping = vma->vm_file->f_mapping;

    + if (vma->vm_flags & VM_SHARED)
    + root = &mapping->i_mmap_shared;
    + else
    + root = &mapping->i_mmap;
    + }
    +
    if (mapping)
    down(&mapping->i_shared_sem);
    spin_lock(&mm->page_table_lock);

    - if (new_below) {
    - vma->vm_start = addr;
    - vma->vm_pgoff += ((addr - new->vm_start) >> PAGE_SHIFT);
    - } else
    - vma->vm_end = addr;
    + if (new_below)
    + __vma_modify(root, vma, addr, vma->vm_end,
    + vma->vm_pgoff + ((addr - new->vm_start) >> PAGE_SHIFT));
    + else
    + __vma_modify(root, vma, vma->vm_start, addr, vma->vm_pgoff);

    __insert_vm_struct(mm, new);

    @@ -1406,7 +1428,7 @@ unsigned long do_brk(unsigned long addr,
    vma->vm_pgoff = 0;
    vma->vm_file = NULL;
    vma->vm_private_data = NULL;
    - INIT_LIST_HEAD(&vma->shared);
    + INIT_VMA_SHARED(vma);

    vma_link(mm, vma, prev, rb_link, rb_parent);

    diff -puN mm/mremap.c~prio_tree_core mm/mremap.c
    --- mmlinux-2.6/mm/mremap.c~prio_tree_core 2004-03-21 16:25:01.000000000 -0500
    +++ mmlinux-2.6-jaya/mm/mremap.c 2004-03-21 16:25:01.000000000 -0500
    @@ -251,7 +251,7 @@ static unsigned long move_vma(struct vm_

    if (allocated_vma) {
    *new_vma = *vma;
    - INIT_LIST_HEAD(&new_vma->shared);
    + INIT_VMA_SHARED(new_vma);
    new_vma->vm_start = new_addr;
    new_vma->vm_end = new_addr+new_len;
    new_vma->vm_pgoff += (addr-vma->vm_start) >> PAGE_SHIFT;
    @@ -309,6 +309,8 @@ unsigned long do_mremap(unsigned long ad
    unsigned long flags, unsigned long new_addr)
    {
    struct vm_area_struct *vma;
    + struct address_space *mapping = NULL;
    + struct prio_tree_root *root = NULL;
    unsigned long ret = -EINVAL;
    unsigned long charged = 0;

    @@ -416,9 +418,24 @@ unsigned long do_mremap(unsigned long ad
    /* can we just expand the current mapping? */
    if (max_addr - addr >= new_len) {
    int pages = (new_len - old_len) >> PAGE_SHIFT;
    +
    + if (vma->vm_file) {
    + mapping = vma->vm_file->f_mapping;
    + if (vma->vm_flags & VM_SHARED)
    + root = &mapping->i_mmap_shared;
    + else
    + root = &mapping->i_mmap;
    + down(&mapping->i_shared_sem);
    + }
    +
    spin_lock(&vma->vm_mm->page_table_lock);
    - vma->vm_end = addr + new_len;
    + __vma_modify(root, vma, vma->vm_start,
    + addr + new_len, vma->vm_pgoff);
    spin_unlock(&vma->vm_mm->page_table_lock);
    +
    + if(mapping)
    + up(&mapping->i_shared_sem);
    +
    current->mm->total_vm += pages;
    if (vma->vm_flags & VM_LOCKED) {
    current->mm->locked_vm += pages;
    diff -puN /dev/null mm/prio_tree.c
    --- /dev/null 2003-01-30 05:24:37.000000000 -0500
    +++ mmlinux-2.6-jaya/mm/prio_tree.c 2004-03-21 16:25:01.000000000 -0500
    @@ -0,0 +1,574 @@
    +/*
    + * mm/prio_tree.c - priority search tree for mapping->i_mmap{,_shared}
    + *
    + * Copyright (C) 2004, Rajesh Venkatasubramanian <vrajesh@umich.edu>
    + *
    + * Based on the radix priority search tree proposed by Edward M. McCreight
    + * SIAM Journal of Computing, vol. 14, no.2, pages 257-276, May 1985
    + *
    + * 02Feb2004 Initial version
    + */
    +
    +#include <linux/init.h>
    +#include <linux/mm.h>
    +#include <linux/prio_tree.h>
    +
    +/*
    + * A clever mix of heap and radix trees forms a radix priority search tree (PST)
    + * which is useful for storing intervals, e.g, we can consider a vma as a closed
    + * interval of file pages [offset_begin, offset_end], and store all vmas that
    + * map a file in a PST. Then, using the PST, we can answer a stabbing query,
    + * i.e., selecting a set of stored intervals (vmas) that overlap with (map) a
    + * given input interval X (a set of consecutive file pages), in "O(log n + m)"
    + * time where 'log n' is the height of the PST, and 'm' is the number of stored
    + * intervals (vmas) that overlap (map) with the input interval X (the set of
    + * consecutive file pages).
    + *
    + * In our implementation, we store closed intervals of the form [radix_index,
    + * heap_index]. We assume that always radix_index <= heap_index. McCreight's PST
    + * is designed for storing intervals with unique radix indices, i.e., each
    + * interval have different radix_index. However, this limitation can be easily
    + * overcome by using the size, i.e., heap_index - radix_index, as part of the
    + * index, so we index the tree using [(radix_index,size), heap_index].
    + *
    + * When the above-mentioned indexing scheme is used, theoretically, in a 32 bit
    + * machine, the maximum height of a PST can be 64. We can use a balanced version
    + * of the priority search tree to optimize the tree height, but the balanced
    + * tree proposed by McCreight is too complex and memory-hungry for our purpose.
    + */
    +
    +static unsigned long index_bits_to_maxindex[BITS_PER_LONG];
    +
    +/*
    + * Maximum heap_index that can be stored in a PST with index_bits bits
    + */
    +static inline unsigned long prio_tree_maxindex(unsigned int bits)
    +{
    + return index_bits_to_maxindex[bits - 1];
    +}
    +
    +/*
    + * Extend a priority search tree so that it can store a node with heap_index
    + * max_heap_index. In the worst case, this algorithm takes O((log n)^2).
    + * However, this function is used rarely and the common case performance is
    + * not bad.
    + */
    +static struct prio_tree_node *prio_tree_expand(struct prio_tree_root *root,
    + struct prio_tree_node *node, unsigned long max_heap_index)
    +{
    + struct prio_tree_node *first = NULL, *prev, *last = NULL;
    +
    + if (max_heap_index > prio_tree_maxindex(root->index_bits))
    + root->index_bits++;
    +
    + while (max_heap_index > prio_tree_maxindex(root->index_bits)) {
    + root->index_bits++;
    +
    + if (prio_tree_empty(root))
    + continue;
    +
    + if (first == NULL) {
    + first = root->prio_tree_node;
    + prio_tree_remove(root, root->prio_tree_node);
    + INIT_PRIO_TREE_NODE(first);
    + last = first;
    + }
    + else {
    + prev = last;
    + last = root->prio_tree_node;
    + prio_tree_remove(root, root->prio_tree_node);
    + INIT_PRIO_TREE_NODE(last);
    + prev->left = last;
    + last->parent = prev;
    + }
    + }
    +
    + INIT_PRIO_TREE_NODE(node);
    +
    + if (first) {
    + node->left = first;
    + first->parent = node;
    + }
    + else
    + last = node;
    +
    + if (!prio_tree_empty(root)) {
    + last->left = root->prio_tree_node;
    + last->left->parent = last;
    + }
    +
    + root->prio_tree_node = node;
    + return node;
    +}
    +
    +/*
    + * Replace a prio_tree_node with a new node and return the old node
    + */
    +static inline struct prio_tree_node *prio_tree_replace(
    + struct prio_tree_root *root, struct prio_tree_node *old,
    + struct prio_tree_node *node)
    +{
    + INIT_PRIO_TREE_NODE(node);
    +
    + if (prio_tree_root(old)) {
    + BUG_ON(root->prio_tree_node != old);
    + /*
    + * We can reduce root->index_bits here. However, it is complex
    + * and does not help much to improve performance (IMO).
    + */
    + node->parent = node;
    + root->prio_tree_node = node;
    + }
    + else {
    + node->parent = old->parent;
    + if (old->parent->left == old)
    + old->parent->left = node;
    + else {
    + BUG_ON(old->parent->right != old);
    + old->parent->right = node;
    + }
    + }
    +
    + if (!prio_tree_left_empty(old)) {
    + node->left = old->left;
    + old->left->parent = node;
    + }
    +
    + if (!prio_tree_right_empty(old)) {
    + node->right = old->right;
    + old->right->parent = node;
    + }
    +
    + return old;
    +}
    +
    +#undef swap
    +#define swap(x,y,z) do {z = x; x = y; y = z; } while (0)
    +
    +/*
    + * Insert a prio_tree_node @node into a radix priority search tree @root. The
    + * algorithm typically takes O(log n) time where 'log n' is the number of bits
    + * required to represent the maximum heap_index. In the worst case, the algo
    + * can take O((log n)^2) - check prio_tree_expand.
    + *
    + * If a prior node with same radix_index and heap_index is already found in
    + * the tree, then returns the address of the prior node. Otherwise, inserts
    + * @node into the tree and returns @node.
    + */
    +
    +struct prio_tree_node *prio_tree_insert(struct prio_tree_root *root,
    + struct prio_tree_node *node)
    +{
    + struct prio_tree_node *cur, *res = node;
    + unsigned long radix_index, heap_index;
    + unsigned long r_index, h_index, index, mask;
    + int size_flag = 0;
    +
    + GET_INDEX(node, radix_index, heap_index);
    +
    + if (prio_tree_empty(root) ||
    + heap_index > prio_tree_maxindex(root->index_bits))
    + return prio_tree_expand(root, node, heap_index);
    +
    + cur = root->prio_tree_node;
    + mask = 1UL << (root->index_bits - 1);
    +
    + while (mask) {
    + GET_INDEX(cur, r_index, h_index);
    +
    + if (r_index == radix_index && h_index == heap_index)
    + return cur;
    +
    + if (h_index < heap_index || (h_index == heap_index &&
    + r_index > radix_index))
    + {
    + struct prio_tree_node *tmp = node;
    + node = prio_tree_replace(root, cur, node);
    + cur = tmp;
    + swap(r_index, radix_index, index);
    + swap(h_index, heap_index, index);
    + }
    +
    + if (size_flag)
    + index = heap_index - radix_index;
    + else
    + index = radix_index;
    +
    + if (index & mask) {
    + if (prio_tree_right_empty(cur)) {
    + INIT_PRIO_TREE_NODE(node);
    + cur->right = node;
    + node->parent = cur;
    + return res;
    + }
    + else
    + cur = cur->right;
    + }
    + else {
    + if (prio_tree_left_empty(cur)) {
    + INIT_PRIO_TREE_NODE(node);
    + cur->left = node;
    + node->parent = cur;
    + return res;
    + }
    + else
    + cur = cur->left;
    + }
    +
    + mask >>= 1;
    +
    + if (!mask) {
    + mask = 1UL << (root->index_bits - 1);
    + size_flag = 1;
    + }
    + }
    + /* Should not reach here */
    + BUG();
    + return NULL;
    +}
    +
    +/*
    + * Remove a prio_tree_node @node from a radix priority search tree @root. The
    + * algorithm takes O(log n) time where 'log n' is the number of bits required
    + * to represent the maximum heap_index.
    + */
    +
    +void prio_tree_remove(struct prio_tree_root *root, struct prio_tree_node *node)
    +{
    + struct prio_tree_node *cur;
    + unsigned long r_index, h_index_right, h_index_left;
    +
    + cur = node;
    +
    + while (!prio_tree_left_empty(cur) || !prio_tree_right_empty(cur)) {
    + if (!prio_tree_left_empty(cur))
    + GET_INDEX(cur->left, r_index, h_index_left);
    + else {
    + cur = cur->right;
    + continue;
    + }
    +
    + if (!prio_tree_right_empty(cur))
    + GET_INDEX(cur->right, r_index, h_index_right);
    + else {
    + cur = cur->left;
    + continue;
    + }
    +
    + /* both h_index_left and h_index_right cannot be 0 */
    + if (h_index_left >= h_index_right)
    + cur = cur->left;
    + else
    + cur = cur->right;
    + }
    +
    + if (prio_tree_root(cur)) {
    + BUG_ON(root->prio_tree_node != cur);
    + *root = PRIO_TREE_ROOT;
    + return;
    + }
    +
    + if (cur->parent->right == cur)
    + cur->parent->right = cur->parent;
    + else {
    + BUG_ON(cur->parent->left != cur);
    + cur->parent->left = cur->parent;
    + }
    +
    + while (cur != node)
    + cur = prio_tree_replace(root, cur->parent, cur);
    +
    + return;
    +}
    +
    +/*
    + * Following functions help to enumerate all prio_tree_nodes in the tree that
    + * overlap with the input interval X [radix_index, heap_index]. The enumeration
    + * takes O(log n + m) time where 'log n' is the height of the tree (which is
    + * proportional to # of bits required to represent the maximum heap_index) and
    + * 'm' is the number of prio_tree_nodes that overlap the interval X.
    + */
    +
    +static inline struct prio_tree_node *__prio_tree_left(
    + struct prio_tree_root *root, struct prio_tree_iter *iter,
    + unsigned long radix_index, unsigned long heap_index,
    + unsigned long *r_index, unsigned long *h_index)
    +{
    + if (prio_tree_left_empty(iter->cur))
    + return NULL;
    +
    + GET_INDEX(iter->cur->left, *r_index, *h_index);
    +
    + if (radix_index <= *h_index) {
    + iter->cur = iter->cur->left;
    + iter->mask >>= 1;
    + if (iter->mask) {
    + if (iter->size_level)
    + iter->size_level++;
    + }
    + else {
    + iter->size_level = 1;
    + iter->mask = 1UL << (root->index_bits - 1);
    + }
    + return iter->cur;
    + }
    +
    + return NULL;
    +}
    +
    +
    +static inline struct prio_tree_node *__prio_tree_right(
    + struct prio_tree_root *root, struct prio_tree_iter *iter,
    + unsigned long radix_index, unsigned long heap_index,
    + unsigned long *r_index, unsigned long *h_index)
    +{
    + unsigned long value;
    +
    + if (prio_tree_right_empty(iter->cur))
    + return NULL;
    +
    + if (iter->size_level)
    + value = iter->value;
    + else
    + value = iter->value | iter->mask;
    +
    + if (heap_index < value)
    + return NULL;
    +
    + GET_INDEX(iter->cur->right, *r_index, *h_index);
    +
    + if (radix_index <= *h_index) {
    + iter->cur = iter->cur->right;
    + iter->mask >>= 1;
    + iter->value = value;
    + if (iter->mask) {
    + if (iter->size_level)
    + iter->size_level++;
    + }
    + else {
    + iter->size_level = 1;
    + iter->mask = 1UL << (root->index_bits - 1);
    + }
    + return iter->cur;
    + }
    +
    + return NULL;
    +}
    +
    +static inline struct prio_tree_node *__prio_tree_parent(
    + struct prio_tree_iter *iter)
    +{
    + iter->cur = iter->cur->parent;
    + iter->mask <<= 1;
    + if (iter->size_level) {
    + if (iter->size_level == 1)
    + iter->mask = 1UL;
    + iter->size_level--;
    + }
    + else if (iter->value & iter->mask)
    + iter->value ^= iter->mask;
    + return iter->cur;
    +}
    +
    +static inline int overlap(unsigned long radix_index, unsigned long heap_index,
    + unsigned long r_index, unsigned long h_index)
    +{
    + if (heap_index < r_index || radix_index > h_index)
    + return 0;
    +
    + return 1;
    +}
    +
    +/*
    + * prio_tree_first:
    + *
    + * Get the first prio_tree_node that overlaps with the interval [radix_index,
    + * heap_index]. Note that always radix_index <= heap_index. We do a pre-order
    + * traversal of the tree.
    + */
    +struct prio_tree_node *prio_tree_first(struct prio_tree_root *root,
    + struct prio_tree_iter *iter, unsigned long radix_index,
    + unsigned long heap_index)
    +{
    + unsigned long r_index, h_index;
    +
    + *iter = PRIO_TREE_ITER;
    +
    + if (prio_tree_empty(root))
    + return NULL;
    +
    + GET_INDEX(root->prio_tree_node, r_index, h_index);
    +
    + if (radix_index > h_index)
    + return NULL;
    +
    + iter->mask = 1UL << (root->index_bits - 1);
    + iter->cur = root->prio_tree_node;
    +
    + while (1) {
    + if (overlap(radix_index, heap_index, r_index, h_index))
    + return iter->cur;
    +
    + if (__prio_tree_left(root, iter, radix_index, heap_index,
    + &r_index, &h_index))
    + continue;
    +
    + if (__prio_tree_right(root, iter, radix_index, heap_index,
    + &r_index, &h_index))
    + continue;
    +
    + break;
    + }
    + return NULL;
    +}
    +
    +/* Get the next prio_tree_node that overlaps with the input interval in iter */
    +struct prio_tree_node *prio_tree_next(struct prio_tree_root *root,
    + struct prio_tree_iter *iter, unsigned long radix_index,
    + unsigned long heap_index)
    +{
    + unsigned long r_index, h_index;
    +
    +repeat:
    + while (__prio_tree_left(root, iter, radix_index, heap_index,
    + &r_index, &h_index))
    + if (overlap(radix_index, heap_index, r_index, h_index))
    + return iter->cur;
    +
    + while (!__prio_tree_right(root, iter, radix_index, heap_index,
    + &r_index, &h_index)) {
    + while (!prio_tree_root(iter->cur) &&
    + iter->cur->parent->right == iter->cur)
    + __prio_tree_parent(iter);
    +
    + if (prio_tree_root(iter->cur))
    + return NULL;
    +
    + __prio_tree_parent(iter);
    + }
    +
    + if (overlap(radix_index, heap_index, r_index, h_index))
    + return iter->cur;
    +
    + goto repeat;
    +}
    +
    +/*
    + * Radix priority search tree for address_space->i_mmap_{_shared}
    + *
    + * For each vma that map a unique set of file pages i.e., unique [radix_index,
    + * heap_index] value, we have a corresponing priority search tree node. If
    + * multiple vmas have identical [radix_index, heap_index] value, then one of
    + * them is used as a tree node and others are stored in a vm_set list. The tree
    + * node points to the first vma (head) of the list using vm_set_head.
    + *
    + * prio_tree_root
    + * |
    + * A vm_set_head
    + * / \ /
    + * L R -> H-I-J-K-M-N-O-P-Q-S
    + * ^ ^ <-- vm_set.list -->
    + * tree nodes
    + *
    + * We need some way to identify whether a vma is a tree node, head of a vm_set
    + * list, or just a member of a vm_set list. We cannot use vm_flags to store
    + * such information. The reason is, in the above figure, it is possible that
    + * vm_flags' of R and H are covered by the different mmap_sems. When R is
    + * removed under R->mmap_sem, H replaces R as a tree node. Since we do not hold
    + * H->mmap_sem, we cannot use H->vm_flags for marking that H is a tree node now.
    + * That's why some trick involving shared.both.parent is used for identifying
    + * tree nodes and list head nodes. We can possibly use the least significant
    + * bit of the vm_set_head field to mark tree and list head nodes. I was worried
    + * about the alignment of vm_area_struct in various architectures.
    + *
    + * vma radix priority search tree node rules:
    + *
    + * vma->shared.both.parent != NULL ==> a tree node
    + *
    + * vma->shared.both.parent == NULL
    + * vma->vm_set_head != NULL ==> list head of vmas that map same pages
    + * vma->vm_set_head == NULL ==> a list node
    + */
    +
    +void __vma_prio_tree_insert(struct prio_tree_root *root,
    + struct vm_area_struct *vma)
    +{
    + struct prio_tree_node *ptr;
    + struct vm_area_struct *old;
    +
    + ptr = prio_tree_insert(root, &vma->shared.prio_tree_node);
    +
    + if (ptr == &vma->shared.prio_tree_node) {
    + vma->vm_set_head = NULL;
    + return;
    + }
    +
    + old = prio_tree_entry(ptr, struct vm_area_struct,
    + shared.prio_tree_node);
    +
    + __vma_prio_tree_add(vma, old);
    +}
    +
    +void __vma_prio_tree_remove(struct prio_tree_root *root,
    + struct vm_area_struct *vma)
    +{
    + struct vm_area_struct *node, *head, *new_head;
    +
    + if (vma->shared.both.parent == NULL && vma->vm_set_head == NULL) {
    + list_del_init(&vma->shared.vm_set.list);
    + INIT_VMA_SHARED(vma);
    + return;
    + }
    +
    + if (vma->vm_set_head) {
    + /* Leave this BUG_ON till prio_tree patch stabilizes */
    + BUG_ON(vma->vm_set_head->vm_set_head != vma);
    + if (vma->shared.both.parent) {
    + head = vma->vm_set_head;
    + if (!list_empty(&head->shared.vm_set.list)) {
    + new_head = list_entry(
    + head->shared.vm_set.list.next,
    + struct vm_area_struct,
    + shared.vm_set.list);
    + list_del_init(&head->shared.vm_set.list);
    + }
    + else
    + new_head = NULL;
    +
    + prio_tree_replace(root, &vma->shared.prio_tree_node,
    + &head->shared.prio_tree_node);
    + head->vm_set_head = new_head;
    + if (new_head)
    + new_head->vm_set_head = head;
    +
    + }
    + else {
    + node = vma->vm_set_head;
    + if (!list_empty(&vma->shared.vm_set.list)) {
    + new_head = list_entry(
    + vma->shared.vm_set.list.next,
    + struct vm_area_struct,
    + shared.vm_set.list);
    + list_del_init(&vma->shared.vm_set.list);
    + node->vm_set_head = new_head;
    + new_head->vm_set_head = node;
    + }
    + else
    + node->vm_set_head = NULL;
    + }
    + INIT_VMA_SHARED(vma);
    + return;
    + }
    +
    + prio_tree_remove(root, &vma->shared.prio_tree_node);
    + INIT_VMA_SHARED(vma);
    +}
    +
    +void __init prio_tree_init(void)
    +{
    + unsigned int i;
    +
    + for (i = 0; i < ARRAY_SIZE(index_bits_to_maxindex) - 1; i++)
    + index_bits_to_maxindex[i] = (1UL << (i + 1)) - 1;
    + index_bits_to_maxindex[ARRAY_SIZE(index_bits_to_maxindex) - 1] = ~0UL;
    +}
    diff -puN mm/shmem.c~prio_tree_core mm/shmem.c
    --- mmlinux-2.6/mm/shmem.c~prio_tree_core 2004-03-21 16:25:01.000000000 -0500
    +++ mmlinux-2.6-jaya/mm/shmem.c 2004-03-21 16:25:01.000000000 -0500
    @@ -1328,7 +1328,7 @@ static void do_shmem_file_read(struct fi
    * virtual addresses, take care about potential aliasing
    * before reading the page on the kernel side.
    */
    - if (!list_empty(&mapping->i_mmap_shared))
    + if (!prio_tree_empty(&mapping->i_mmap_shared))
    flush_dcache_page(page);
    /*
    * Mark the page accessed if we read the beginning.
    diff -puN mm/swap_state.c~prio_tree_core mm/swap_state.c
    --- mmlinux-2.6/mm/swap_state.c~prio_tree_core 2004-03-21 16:25:01.000000000 -0500
    +++ mmlinux-2.6-jaya/mm/swap_state.c 2004-03-21 16:25:01.000000000 -0500
    @@ -32,8 +32,8 @@ struct address_space swapper_space = {
    .locked_pages = LIST_HEAD_INIT(swapper_space.locked_pages),
    .a_ops = &swap_aops,
    .backing_dev_info = &swap_backing_dev_info,
    - .i_mmap = LIST_HEAD_INIT(swapper_space.i_mmap),
    - .i_mmap_shared = LIST_HEAD_INIT(swapper_space.i_mmap_shared),
    + .i_mmap = PRIO_TREE_ROOT_INIT,
    + .i_mmap_shared = PRIO_TREE_ROOT_INIT,
    .i_shared_sem = __MUTEX_INITIALIZER(swapper_space.i_shared_sem),
    .truncate_count = ATOMIC_INIT(0),
    .private_lock = SPIN_LOCK_UNLOCKED,
    diff -puN mm/vmscan.c~prio_tree_core mm/vmscan.c
    --- mmlinux-2.6/mm/vmscan.c~prio_tree_core 2004-03-21 16:25:01.000000000 -0500
    +++ mmlinux-2.6-jaya/mm/vmscan.c 2004-03-21 16:25:01.000000000 -0500
    @@ -191,9 +191,9 @@ static inline int page_mapping_inuse(str
    return 1;

    /* File is mmap'd by somebody. */
    - if (!list_empty(&mapping->i_mmap))
    + if (!prio_tree_empty(&mapping->i_mmap))
    return 1;
    - if (!list_empty(&mapping->i_mmap_shared))
    + if (!prio_tree_empty(&mapping->i_mmap_shared))
    return 1;

    return 0;
    _

    -
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