The patch titled
memcg: fix behavior under memory.limit equals to memsw.limit
has been added to the -mm tree. Its filename is
memcg-fix-behavior-under-memorylimit-equals-to-memswlimit.patch
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Subject: memcg: fix behavior under memory.limit equals to memsw.limit
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
A user can set memcg.limit_in_bytes == memcg.memsw.limit_in_bytes when the
user just want to limit the total size of applications, in other words,
not very interested in memory usage itself. In this case, swap-out will
be done only by global-LRU.
But, under current implementation, memory.limit_in_bytes is checked at
first and try_to_free_page() may do swap-out. But, that swap-out is
useless for memsw.limit_in_bytes and the thread may hit limit again.
This patch tries to fix the current behavior at memory.limit ==
memsw.limit case. And documentation is updated to explain the behavior of
this special case.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
Cc: Balbir Singh <balbir@xxxxxxxxxx>
Cc: Li Zefan <lizf@xxxxxxxxxxxxxx>
Cc: Dhaval Giani <dhaval@xxxxxxxxxxxxxxxxxx>
Cc: YAMAMOTO Takashi <yamamoto@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/cgroups/memory.txt | 17 +++++++++++------
mm/memcontrol.c | 19 +++++++++++++++++++
2 files changed, 30 insertions(+), 6 deletions(-)
diff -puN Documentation/cgroups/memory.txt~memcg-fix-behavior-under-memorylimit-equals-to-memswlimit Documentation/cgroups/memory.txt
--- a/Documentation/cgroups/memory.txt~memcg-fix-behavior-under-memorylimit-equals-to-memswlimit
+++ a/Documentation/cgroups/memory.txt
@@ -152,14 +152,19 @@ When swap is accounted, following files
usage of mem+swap is limited by memsw.limit_in_bytes.
-Note: why 'mem+swap' rather than swap.
+* why 'mem+swap' rather than swap.
The global LRU(kswapd) can swap out arbitrary pages. Swap-out means
to move account from memory to swap...there is no change in usage of
-mem+swap.
-
-In other words, when we want to limit the usage of swap without affecting
-global LRU, mem+swap limit is better than just limiting swap from OS point
-of view.
+mem+swap. In other words, when we want to limit the usage of swap without
+affecting global LRU, mem+swap limit is better than just limiting swap from
+OS point of view.
+
+* What happens when a cgroup hits memory.memsw.limit_in_bytes
+When a cgroup his memory.memsw.limit_in_bytes, it's useless to do swap-out
+in this cgroup. Then, swap-out will not be done by cgroup routine and file
+caches are dropped. But as mentioned above, global LRU can do swapout memory
+from it for sanity of the system's memory management state. You can't forbid
+it by cgroup.
2.5 Reclaim
diff -puN mm/memcontrol.c~memcg-fix-behavior-under-memorylimit-equals-to-memswlimit mm/memcontrol.c
--- a/mm/memcontrol.c~memcg-fix-behavior-under-memorylimit-equals-to-memswlimit
+++ a/mm/memcontrol.c
@@ -177,6 +177,9 @@ struct mem_cgroup {
unsigned int swappiness;
+ /* set when res.limit == memsw.limit */
+ bool memsw_is_minimum;
+
/*
* statistics. This must be placed at the end of memcg.
*/
@@ -847,6 +850,10 @@ static int mem_cgroup_hierarchical_recla
int ret, total = 0;
int loop = 0;
+ /* If memsw_is_minimum==1, swap-out is of-no-use. */
+ if (root_mem->memsw_is_minimum)
+ noswap = true;
+
while (loop < 2) {
victim = mem_cgroup_select_victim(root_mem);
if (victim == root_mem)
@@ -1752,6 +1759,12 @@ static int mem_cgroup_resize_limit(struc
break;
}
ret = res_counter_set_limit(&memcg->res, val);
+ if (!ret) {
+ if (memswlimit == val)
+ memcg->memsw_is_minimum = true;
+ else
+ memcg->memsw_is_minimum = false;
+ }
mutex_unlock(&set_limit_mutex);
if (!ret)
@@ -1799,6 +1812,12 @@ static int mem_cgroup_resize_memsw_limit
break;
}
ret = res_counter_set_limit(&memcg->memsw, val);
+ if (!ret) {
+ if (memlimit == val)
+ memcg->memsw_is_minimum = true;
+ else
+ memcg->memsw_is_minimum = false;
+ }
mutex_unlock(&set_limit_mutex);
if (!ret)
_
Patches currently in -mm which might be from kamezawa.hiroyu@xxxxxxxxxxxxxx are
migration-only-migrate_prep-once-per-move_pages.patch
page-allocator-use-integer-fields-lookup-for-gfp_zone-and-check-for-errors-in-flags-passed-to-the-page-allocator.patch
page-allocator-use-integer-fields-lookup-for-gfp_zone-and-check-for-errors-in-flags-passed-to-the-page-allocator-fix-gfp-zone-patch.patch
mm-add-swap-cache-interface-for-swap-reference.patch
mm-modify-swap_map-and-add-swap_has_cache-flag.patch
mm-modify-swap_map-and-add-swap_has_cache-flag-update.patch
mm-reuse-unused-swap-entry-if-necessary.patch
mm-reuse-unused-swap-entry-if-necessary-update.patch
cgroups-forbid-noprefix-if-mounting-more-than-just-cpuset-subsystem.patch
cgroups-forbid-noprefix-if-mounting-more-than-just-cpuset-subsystem-fix.patch
cgroups-forbid-noprefix-if-mounting-more-than-just-cpuset-subsystem-fix2.patch
memcg-add-file-based-rss-accounting.patch
memcg-add-file-based-rss-accounting-fix-mem_cgroup_update_mapped_file_stat-oops.patch
memcg-remove-mem_cgroup_cache_charge_swapin.patch
memcg-remove-some-redundant-checks.patch
memcg-remove-unneeded-forward-declaration-from-schedh.patch
memcg-fix-swap-accounting.patch
memcg-fix-swap-accounting-update.patch
memcg-fix-behavior-under-memorylimit-equals-to-memswlimit.patch
--
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