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Subject[PATCH -mm 3/5] memcg: helper function for relcaim from shmem.
A new call, mem_cgroup_shrink_usage() is added for shmem handling
and relacing non-standard usage of mem_cgroup_charge/uncharge.

Now, shmem calls mem_cgroup_charge() just for reclaim some pages from
mem_cgroup. In general, shmem is used by some process group and not for
global resource (like file caches). So, it's reasonable to reclaim pages from
mem_cgroup where shmem is mainly used.

Changelog v3->v4
- fixed while loop to be do_while loop.
- fixed declaration in header file.
- adjusted to 2.6.26-rc2-mm1

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

---
include/linux/memcontrol.h | 7 +++++++
mm/memcontrol.c | 25 +++++++++++++++++++++++++
mm/shmem.c | 5 ++---
3 files changed, 34 insertions(+), 3 deletions(-)

Index: mm-2.6.26-rc2-mm1/mm/memcontrol.c
===================================================================
--- mm-2.6.26-rc2-mm1.orig/mm/memcontrol.c
+++ mm-2.6.26-rc2-mm1/mm/memcontrol.c
@@ -770,6 +770,31 @@ void mem_cgroup_end_migration(struct pag
}

/*
+ * A call to try to shrink memory usage under specified resource controller.
+ * This is typically used for page reclaiming for shmem for reducing side
+ * effect of page allocation from shmem, which is used by some mem_cgroup.
+ */
+int mem_cgroup_shrink_usage(struct mm_struct *mm, gfp_t gfp_mask)
+{
+ struct mem_cgroup *mem;
+ int progress = 0;
+ int retry = MEM_CGROUP_RECLAIM_RETRIES;
+
+ rcu_read_lock();
+ mem = mem_cgroup_from_task(rcu_dereference(mm->owner));
+ css_get(&mem->css);
+ rcu_read_unlock();
+
+ do {
+ progress = try_to_free_mem_cgroup_pages(mem, gfp_mask);
+ } while (!progress && --retry);
+
+ if (!retry)
+ return -ENOMEM;
+ return 0;
+}
+
+/*
* This routine traverse page_cgroup in given list and drop them all.
* *And* this routine doesn't reclaim page itself, just removes page_cgroup.
*/
Index: mm-2.6.26-rc2-mm1/mm/shmem.c
===================================================================
--- mm-2.6.26-rc2-mm1.orig/mm/shmem.c
+++ mm-2.6.26-rc2-mm1/mm/shmem.c
@@ -1321,13 +1321,12 @@ repeat:
unlock_page(swappage);
if (error == -ENOMEM) {
/* allow reclaim from this memory cgroup */
- error = mem_cgroup_cache_charge(swappage,
- current->mm, gfp & ~__GFP_HIGHMEM);
+ error = mem_cgroup_shrink_usage(current->mm,
+ gfp & ~__GFP_HIGHMEM);
if (error) {
page_cache_release(swappage);
goto failed;
}
- mem_cgroup_uncharge_cache_page(swappage);
}
page_cache_release(swappage);
goto repeat;
Index: mm-2.6.26-rc2-mm1/include/linux/memcontrol.h
===================================================================
--- mm-2.6.26-rc2-mm1.orig/include/linux/memcontrol.h
+++ mm-2.6.26-rc2-mm1/include/linux/memcontrol.h
@@ -37,6 +37,8 @@ extern int mem_cgroup_cache_charge(struc
extern void mem_cgroup_uncharge_page(struct page *page);
extern void mem_cgroup_uncharge_cache_page(struct page *page);
extern void mem_cgroup_move_lists(struct page *page, bool active);
+extern int mem_cgroup_shrink_usage(struct mm_struct *mm, gfp_t gfp_mask);
+
extern unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
struct list_head *dst,
unsigned long *scanned, int order,
@@ -102,6 +104,11 @@ static inline void mem_cgroup_uncharge_c
{
}

+static inline int mem_cgroup_shrink_usage(struct mm_struct *mm, gfp_t gfp_mask)
+{
+ return 0;
+}
+
static inline void mem_cgroup_move_lists(struct page *page, bool active)
{
}


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