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SubjectRe: Control page reclaim granularity
Date
Zheng Liu <gnehzuil.liu@gmail.com> writes:
> Hi Greg,
>
> Sorry, I forgot to say that I don't subscribe linux-mm and linux-kernel
> mailing list. So please Cc me.
>
> I am glad to receive your reply and I am very interesting for your
> approach. Actually I am not very familiar with CGroup. So would you
> please send your patch to me if you can? Thank you all the same.
>
> Regards,
> Zheng

Sorry for the delay, I had trouble finding my old prototype patch. The
patch below is based on v2.6.34. The patch is just an idea not a
complete solution.

From b1b127e0e1443446d51353b0d7a776bddc046009 Mon Sep 17 00:00:00 2001
From: Greg Thelen <gthelen@google.com>
Date: Sat, 5 Jun 2010 17:26:06 -0700
Subject: [PATCH] memcg: prototype of dentry/cgroup binding.

JUST A PROTOTYPE: DO NOT SUBMIT

This creates a /dev/cgroup/memory/X/memory.dir_roots file which one can
use to register a directory file descriptors. The idea is that future
charges to registered directories, including child inodes, will be
billed to memcg X rather than whatever memcg the faulting process runs
within.
---
fs/dcache.c | 4 +++
include/linux/dcache.h | 1 +
include/linux/memcontrol.h | 2 +-
mm/filemap.c | 3 ++
mm/memcontrol.c | 64 ++++++++++++++++++++++++++++++++++++++++++++
5 files changed, 73 insertions(+), 1 deletions(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index f1358e5..dda48d7 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -70,6 +70,7 @@ struct dentry_stat_t dentry_stat = {
static void __d_free(struct dentry *dentry)
{
WARN_ON(!list_empty(&dentry->d_alias));
+ BUG_ON(dentry->d_mem);
if (dname_external(dentry))
kfree(dentry->d_name.name);
kmem_cache_free(dentry_cache, dentry);
@@ -172,6 +173,7 @@ static struct dentry *d_kill(struct dentry *dentry)
struct dentry *parent;

list_del(&dentry->d_u.d_child);
+ mem_cgroup_disassociate_from_dentry(dentry);
dentry_stat.nr_dentry--; /* For d_free, below */
/*drops the locks, at that point nobody can reach this dentry */
dentry_iput(dentry);
@@ -953,6 +955,7 @@ struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
dentry->d_inode = NULL;
dentry->d_parent = NULL;
dentry->d_sb = NULL;
+ dentry->d_mem = NULL;
dentry->d_op = NULL;
dentry->d_fsdata = NULL;
dentry->d_mounted = 0;
@@ -964,6 +967,7 @@ struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
if (parent) {
dentry->d_parent = dget(parent);
dentry->d_sb = parent->d_sb;
+ dentry->d_mem = parent->d_mem;
} else {
INIT_LIST_HEAD(&dentry->d_u.d_child);
}
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index eebb617..523d58b 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -114,6 +114,7 @@ struct dentry {
unsigned long d_time; /* used by d_revalidate */
const struct dentry_operations *d_op;
struct super_block *d_sb; /* The root of the dentry tree */
+ struct mem_cgroup *d_mem; /* Optional memcg */
void *d_fsdata; /* fs-specific data */

unsigned char d_iname[DNAME_INLINE_LEN_MIN]; /* small names */
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 44301c6..a8b54f9 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -71,6 +71,7 @@ extern unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
struct mem_cgroup *mem_cont,
int active, int file);
extern void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask);
+void mem_cgroup_disassociate_from_dentry(struct dentry *dentry);
int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem);

extern struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page);
@@ -309,4 +310,3 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
#endif /* CONFIG_CGROUP_MEM_CONT */

#endif /* _LINUX_MEMCONTROL_H */
-
diff --git a/mm/filemap.c b/mm/filemap.c
index 140ebda..a9a525b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -400,8 +400,11 @@ int add_to_page_cache_locked(struct page *page, struct address_space *mapping,

VM_BUG_ON(!PageLocked(page));

+ VM_BUG_ON(page->mapping != NULL);
+ page->mapping = mapping; /* XXX: hack? */
error = mem_cgroup_cache_charge(page, current->mm,
gfp_mask & GFP_RECLAIM_MASK);
+ page->mapping = NULL; /* XXX: hack? */
if (error)
goto out;

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 8a79a6f..de9f150 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -793,6 +793,23 @@ void mem_cgroup_move_lists(struct page *page,
mem_cgroup_add_lru_list(page, to);
}

+static void mem_cgroup_associate_dentry(struct mem_cgroup *mem,
+ struct dentry *dentry)
+{
+ css_get(&mem->css);
+ BUG_ON(dentry->d_mem);
+ dentry->d_mem = mem;
+}
+
+void mem_cgroup_disassociate_from_dentry(struct dentry *dentry)
+{
+ if (!dentry->d_mem)
+ return;
+
+ css_put(&dentry->d_mem->css);
+ dentry->d_mem = NULL;
+}
+
int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
{
int ret;
@@ -1914,6 +1931,29 @@ static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm,
return 0;
prefetchw(pc);

+ /*
+ * If the page is inode and related dentry indicates a cgroup, then
+ * charge that cgroup. Otherwise fallback on the mm's cgroup.
+ *
+ * TODO(gthelen): this needs more thought.
+ */
+ if ((memcg == NULL) && !PageAnon(page)) {
+ struct address_space *as;
+ struct inode *inode;
+ struct dentry *dentry;
+
+ /* what kind of locking is needed to walk this? dcache_lock (gulp)? */
+ as = (struct address_space *)page_rmapping(page);
+ if (as != NULL) {
+ inode = as->host;
+ BUG_ON(inode == NULL);
+ list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
+ memcg = dentry->d_mem;
+ break;
+ }
+ }
+ }
+
mem = memcg;
ret = __mem_cgroup_try_charge(mm, gfp_mask, &mem, true);
if (ret || !mem)
@@ -3539,6 +3579,26 @@ unlock:
return ret;
}

+static int mem_cgroup_dir_roots_write(struct cgroup *cgrp, struct cftype *cft,
+ u64 dir_fd)
+{
+ struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
+ struct file *dir;
+ int status = 0;
+
+ dir = fget(dir_fd);
+ if (!dir)
+ return -EINVAL;
+
+ if (dir->f_dentry->d_mem)
+ status = -EINVAL;
+ else
+ mem_cgroup_associate_dentry(mem, dir->f_dentry);
+
+ fput(dir);
+ return status;
+}
+
static struct cftype mem_cgroup_files[] = {
{
.name = "usage_in_bytes",
@@ -3594,6 +3654,10 @@ static struct cftype mem_cgroup_files[] = {
.read_u64 = mem_cgroup_move_charge_read,
.write_u64 = mem_cgroup_move_charge_write,
},
+ {
+ .name = "dir_roots",
+ .write_u64 = mem_cgroup_dir_roots_write,
+ },
};

#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
--
1.7.7.3


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