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Subject[PATCH V5] Cleancache: shim to Xen Transcendent Memory
[PATCH V5] Cleancache: shim to Xen Transcendent Memory

Changes from V0 to V5:
- uses new in-kernel cleancache API to match cleancache V5 patch
- uses new Xen tmem ABI (v1) just pushed upstream to Xen
(skipped V1-V4 to match cleancache version numbers)

This companion patch to the cleancache V5 patchset (see
http://lkml.org/lkml/2010/9/3/383) provides one consumer
for the proposed cleancache internal kernel API. This
user is Xen Transcendent Memory ("tmem"), supported in Xen 4.0+.
(A second user, zmem, was separately posted by Nitin Gupta
and is not yet updated to cleancache V5.)

This patch affects Xen directories only; while broader review
is welcome, the patch is provided primarily to answer concerns
expressed about the apparent non-existence of consumers for
the proposed cleancache patch.

Xen tmem provides "hypervisor RAM" as an ephemeral page-oriented
pseudo-RAM store for cleancache pages, shared cleancache pages,
and frontswap pages. Tmem provides enterprise-quality concurrency,
full save/restore and live migration support, compression
and deduplication.

A presentation showing up to 8% faster performance and up to 52%
reduction in sectors read on a kernel compile workload, despite
aggressive in-kernel page reclamation ("self-ballooning") can be
found at:

http://oss.oracle.com/projects/tmem/dist/documentation/presentations/TranscendentMemoryXenSummit2010.pdf

Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>

Diffstat:
arch/x86/include/asm/xen/hypercall.h | 7
drivers/xen/Makefile | 1
drivers/xen/tmem.c | 264 +++++++++++++++++++++
include/xen/interface/xen.h | 22 +
4 files changed, 294 insertions(+)
diff -Napur linux-2.6.36-rc3/arch/x86/include/asm/xen/hypercall.h linux-2.6.36-rc3-cleancache_tmem_only/arch/x86/include/asm/xen/hypercall.h
--- linux-2.6.36-rc3/arch/x86/include/asm/xen/hypercall.h 2010-08-29 09:36:04.000000000 -0600
+++ linux-2.6.36-rc3-cleancache_tmem_only/arch/x86/include/asm/xen/hypercall.h 2010-09-02 14:30:25.000000000 -0600
@@ -423,6 +423,13 @@ HYPERVISOR_hvm_op(int op, void *arg)
return _hypercall2(unsigned long, hvm_op, op, arg);
}

+static inline int
+HYPERVISOR_tmem_op(
+ struct tmem_op *op)
+{
+ return _hypercall1(int, tmem_op, op);
+}
+
static inline void
MULTI_fpu_taskswitch(struct multicall_entry *mcl, int set)
{
diff -Napur linux-2.6.36-rc3/drivers/xen/Makefile linux-2.6.36-rc3-cleancache_tmem_only/drivers/xen/Makefile
--- linux-2.6.36-rc3/drivers/xen/Makefile 2010-08-29 09:36:04.000000000 -0600
+++ linux-2.6.36-rc3-cleancache_tmem_only/drivers/xen/Makefile 2010-09-02 14:30:47.000000000 -0600
@@ -1,5 +1,6 @@
obj-y += grant-table.o features.o events.o manage.o
obj-y += xenbus/
+obj-y += tmem.o

nostackp := $(call cc-option, -fno-stack-protector)
CFLAGS_features.o := $(nostackp)
diff -Napur linux-2.6.36-rc3/drivers/xen/tmem.c linux-2.6.36-rc3-cleancache_tmem_only/drivers/xen/tmem.c
--- linux-2.6.36-rc3/drivers/xen/tmem.c 1969-12-31 17:00:00.000000000 -0700
+++ linux-2.6.36-rc3-cleancache_tmem_only/drivers/xen/tmem.c 2010-09-02 16:07:11.000000000 -0600
@@ -0,0 +1,264 @@
+/*
+ * Xen implementation for transcendent memory (tmem)
+ *
+ * Copyright (C) 2009-2010 Oracle Corp. All rights reserved.
+ * Author: Dan Magenheimer
+ */
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/pagemap.h>
+#include <linux/cleancache.h>
+
+#include <xen/xen.h>
+#include <xen/interface/xen.h>
+#include <asm/xen/hypercall.h>
+#include <asm/xen/page.h>
+#include <asm/xen/hypervisor.h>
+
+#define TMEM_CONTROL 0
+#define TMEM_NEW_POOL 1
+#define TMEM_DESTROY_POOL 2
+#define TMEM_NEW_PAGE 3
+#define TMEM_PUT_PAGE 4
+#define TMEM_GET_PAGE 5
+#define TMEM_FLUSH_PAGE 6
+#define TMEM_FLUSH_OBJECT 7
+#define TMEM_READ 8
+#define TMEM_WRITE 9
+#define TMEM_XCHG 10
+
+/* Bits for HYPERVISOR_tmem_op(TMEM_NEW_POOL) */
+#define TMEM_POOL_PERSIST 1
+#define TMEM_POOL_SHARED 2
+#define TMEM_POOL_PAGESIZE_SHIFT 4
+#define TMEM_VERSION_SHIFT 24
+
+
+struct tmem_pool_uuid {
+ u64 uuid_lo;
+ u64 uuid_hi;
+};
+
+struct tmem_oid {
+ u64 oid[3];
+};
+
+#define TMEM_POOL_PRIVATE_UUID { 0, 0 }
+
+/* flags for tmem_ops.new_pool */
+#define TMEM_POOL_PERSIST 1
+#define TMEM_POOL_SHARED 2
+
+/* xen tmem foundation ops/hypercalls */
+
+static inline int xen_tmem_op(u32 tmem_cmd, u32 tmem_pool, struct tmem_oid oid,
+ u32 index, unsigned long gmfn, u32 tmem_offset, u32 pfn_offset, u32 len)
+{
+ struct tmem_op op;
+ int rc = 0;
+
+ op.cmd = tmem_cmd;
+ op.pool_id = tmem_pool;
+ op.u.gen.oid[0] = oid.oid[0];
+ op.u.gen.oid[1] = oid.oid[1];
+ op.u.gen.oid[2] = oid.oid[2];
+ op.u.gen.index = index;
+ op.u.gen.tmem_offset = tmem_offset;
+ op.u.gen.pfn_offset = pfn_offset;
+ op.u.gen.len = len;
+ set_xen_guest_handle(op.u.gen.gmfn, (void *)gmfn);
+ rc = HYPERVISOR_tmem_op(&op);
+ return rc;
+}
+
+static int xen_tmem_new_pool(struct tmem_pool_uuid uuid,
+ u32 flags, unsigned long pagesize)
+{
+ struct tmem_op op;
+ int rc = 0, pageshift;
+
+ for (pageshift = 0; pagesize != 1; pageshift++)
+ pagesize >>= 1;
+ flags |= (pageshift - 12) << TMEM_POOL_PAGESIZE_SHIFT;
+ flags |= TMEM_SPEC_VERSION << TMEM_VERSION_SHIFT;
+ op.cmd = TMEM_NEW_POOL;
+ op.u.new.uuid[0] = uuid.uuid_lo;
+ op.u.new.uuid[1] = uuid.uuid_hi;
+ op.u.new.flags = flags;
+ rc = HYPERVISOR_tmem_op(&op);
+ return rc;
+}
+
+/* xen generic tmem ops */
+
+static int xen_tmem_put_page(u32 pool_id, struct tmem_oid oid,
+ u32 index, unsigned long pfn)
+{
+ unsigned long gmfn = xen_pv_domain() ? pfn_to_mfn(pfn) : pfn;
+
+ return xen_tmem_op(TMEM_PUT_PAGE, pool_id, oid, index,
+ gmfn, 0, 0, 0);
+}
+
+static int xen_tmem_get_page(u32 pool_id, struct tmem_oid oid,
+ u32 index, unsigned long pfn)
+{
+ unsigned long gmfn = xen_pv_domain() ? pfn_to_mfn(pfn) : pfn;
+
+ return xen_tmem_op(TMEM_GET_PAGE, pool_id, oid, index,
+ gmfn, 0, 0, 0);
+}
+
+static int xen_tmem_flush_page(u32 pool_id, struct tmem_oid oid, u32 index)
+{
+ return xen_tmem_op(TMEM_FLUSH_PAGE, pool_id, oid, index,
+ 0, 0, 0, 0);
+}
+
+static int xen_tmem_flush_object(u32 pool_id, struct tmem_oid oid)
+{
+ return xen_tmem_op(TMEM_FLUSH_OBJECT, pool_id, oid, 0, 0, 0, 0, 0);
+}
+
+static int xen_tmem_destroy_pool(u32 pool_id)
+{
+ struct tmem_oid oid = { { 0 } };
+
+ return xen_tmem_op(TMEM_DESTROY_POOL, pool_id, oid, 0, 0, 0, 0, 0);
+}
+
+int tmem_enabled;
+
+static int __init enable_tmem(char *s)
+{
+ tmem_enabled = 1;
+ return 1;
+}
+
+__setup("tmem", enable_tmem);
+
+/* cleancache ops */
+
+static void tmem_cleancache_put_page(int pool, struct cleancache_filekey key,
+ pgoff_t index, struct page *page)
+{
+ u32 ind = (u32) index;
+ struct tmem_oid oid = *(struct tmem_oid *)&key;
+ unsigned long pfn = page_to_pfn(page);
+
+ if (pool < 0)
+ return;
+ if (ind != index)
+ return;
+ mb(); /* ensure page is quiescent; tmem may address it with an alias */
+ (void)xen_tmem_put_page((u32)pool, oid, ind, pfn);
+}
+
+static int tmem_cleancache_get_page(int pool, struct cleancache_filekey key,
+ pgoff_t index, struct page *page)
+{
+ u32 ind = (u32) index;
+ struct tmem_oid oid = *(struct tmem_oid *)&key;
+ unsigned long pfn = page_to_pfn(page);
+ int ret;
+
+ /* translate return values to linux semantics */
+ if (pool < 0)
+ return -1;
+ if (ind != index)
+ return -1;
+ ret = xen_tmem_get_page((u32)pool, oid, ind, pfn);
+ if (ret == 1)
+ return 0;
+ else
+ return -1;
+}
+
+static void tmem_cleancache_flush_page(int pool, struct cleancache_filekey key,
+ pgoff_t index)
+{
+ u32 ind = (u32) index;
+ struct tmem_oid oid = *(struct tmem_oid *)&key;
+
+ if (pool < 0)
+ return;
+ if (ind != index)
+ return;
+ (void)xen_tmem_flush_page((u32)pool, oid, ind);
+}
+
+static void tmem_cleancache_flush_inode(int pool, struct cleancache_filekey key)
+{
+ struct tmem_oid oid = *(struct tmem_oid *)&key;
+
+ if (pool < 0)
+ return;
+ (void)xen_tmem_flush_object((u32)pool, oid);
+}
+
+static void tmem_cleancache_flush_fs(int pool)
+{
+ if (pool < 0)
+ return;
+ (void)xen_tmem_destroy_pool((u32)pool);
+}
+
+static int tmem_cleancache_init_fs(size_t pagesize)
+{
+ struct tmem_pool_uuid uuid_private = TMEM_POOL_PRIVATE_UUID;
+
+ return xen_tmem_new_pool(uuid_private, 0, pagesize);
+}
+
+static int tmem_cleancache_init_shared_fs(char *uuid, size_t pagesize)
+{
+ struct tmem_pool_uuid shared_uuid;
+
+ shared_uuid.uuid_lo = *(u64 *)uuid;
+ shared_uuid.uuid_hi = *(u64 *)(&uuid[8]);
+ return xen_tmem_new_pool(shared_uuid, TMEM_POOL_SHARED, pagesize);
+}
+
+static int use_cleancache = 1;
+
+static int __init no_cleancache(char *s)
+{
+ use_cleancache = 0;
+ return 1;
+}
+
+__setup("nocleancache", no_cleancache);
+
+static struct cleancache_ops tmem_cleancache_ops = {
+ .put_page = tmem_cleancache_put_page,
+ .get_page = tmem_cleancache_get_page,
+ .flush_page = tmem_cleancache_flush_page,
+ .flush_inode = tmem_cleancache_flush_inode,
+ .flush_fs = tmem_cleancache_flush_fs,
+ .init_shared_fs = tmem_cleancache_init_shared_fs,
+ .init_fs = tmem_cleancache_init_fs
+};
+
+static int __init xen_tmem_init(void)
+{
+ struct cleancache_ops old_ops;
+
+ if (!xen_domain())
+ return 0;
+#ifdef CONFIG_CLEANCACHE
+ BUG_ON(sizeof(struct cleancache_filekey) != sizeof(struct tmem_oid));
+ if (tmem_enabled && use_cleancache) {
+ char *s = "";
+ old_ops = cleancache_register_ops(&tmem_cleancache_ops);
+ if (old_ops.init_fs != NULL)
+ s = " (WARNING: cleancache_ops overridden)";
+ printk(KERN_INFO "cleancache enabled, RAM provided by "
+ "Xen Transcendent Memory%s\n",s);
+ }
+#endif
+ return 0;
+}
+
+module_init(xen_tmem_init)
diff -Napur linux-2.6.36-rc3/include/xen/interface/xen.h linux-2.6.36-rc3-cleancache_tmem_only/include/xen/interface/xen.h
--- linux-2.6.36-rc3/include/xen/interface/xen.h 2010-08-29 09:36:04.000000000 -0600
+++ linux-2.6.36-rc3-cleancache_tmem_only/include/xen/interface/xen.h 2010-09-02 14:31:42.000000000 -0600
@@ -58,6 +58,7 @@
#define __HYPERVISOR_event_channel_op 32
#define __HYPERVISOR_physdev_op 33
#define __HYPERVISOR_hvm_op 34
+#define __HYPERVISOR_tmem_op 38

/* Architecture-specific hypercall definitions. */
#define __HYPERVISOR_arch_0 48
@@ -461,6 +462,27 @@ typedef uint8_t xen_domain_handle_t[16];
#define __mk_unsigned_long(x) x ## UL
#define mk_unsigned_long(x) __mk_unsigned_long(x)

+#define TMEM_SPEC_VERSION 1
+
+struct tmem_op {
+ uint32_t cmd;
+ int32_t pool_id;
+ union {
+ struct { /* for cmd == TMEM_NEW_POOL */
+ uint64_t uuid[2];
+ uint32_t flags;
+ } new;
+ struct {
+ uint64_t oid[3];
+ uint32_t index;
+ uint32_t tmem_offset;
+ uint32_t pfn_offset;
+ uint32_t len;
+ GUEST_HANDLE(void) gmfn; /* guest machine page frame */
+ } gen;
+ } u;
+};
+
#else /* __ASSEMBLY__ */

/* In assembly code we cannot use C numeric constant suffixes. */
--- linux-2.6.36-rc3/fs/ocfs2/super.c 2010-08-29 09:36:04.000000000 -0600
+++ linux-2.6.36-rc3-cleancache/fs/ocfs2/super.c 2010-08-30 09:20:43.000000000 -0600
@@ -42,6 +42,7 @@
#include <linux/seq_file.h>
#include <linux/quotaops.h>
#include <linux/smp_lock.h>
+#include <linux/cleancache.h>

#define MLOG_MASK_PREFIX ML_SUPER
#include <cluster/masklog.h>
@@ -2284,6 +2285,8 @@ static int ocfs2_initialize_super(struct
mlog_errno(status);
goto bail;
}
+ sb->cleancache_poolid =
+ cleancache_init_shared_fs((char *)&uuid_net_key, PAGE_SIZE);

bail:
mlog_exit(status);

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