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authorRoman Gushchin <guro@fb.com>2018-06-07 17:07:46 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-06-07 17:34:36 -0700
commitbf8d5d52ffe89aac5b46ddb39dd1a4351fae5df4 (patch)
treee0b0457ddf128b0562eb403762b2f2de2292e8b1 /mm/vmscan.c
parentfb52bbaee598f58352d8732637ebe7013b2df79f (diff)
memcg: introduce memory.min
Memory controller implements the memory.low best-effort memory protection mechanism, which works perfectly in many cases and allows protecting working sets of important workloads from sudden reclaim. But its semantics has a significant limitation: it works only as long as there is a supply of reclaimable memory. This makes it pretty useless against any sort of slow memory leaks or memory usage increases. This is especially true for swapless systems. If swap is enabled, memory soft protection effectively postpones problems, allowing a leaking application to fill all swap area, which makes no sense. The only effective way to guarantee the memory protection in this case is to invoke the OOM killer. It's possible to handle this case in userspace by reacting on MEMCG_LOW events; but there is still a place for a fail-safe in-kernel mechanism to provide stronger guarantees. This patch introduces the memory.min interface for cgroup v2 memory controller. It works very similarly to memory.low (sharing the same hierarchical behavior), except that it's not disabled if there is no more reclaimable memory in the system. If cgroup is not populated, its memory.min is ignored, because otherwise even the OOM killer wouldn't be able to reclaim the protected memory, and the system can stall. [guro@fb.com: s/low/min/ in docs] Link: http://lkml.kernel.org/r/20180510130758.GA9129@castle.DHCP.thefacebook.com Link: http://lkml.kernel.org/r/20180509180734.GA4856@castle.DHCP.thefacebook.com Signed-off-by: Roman Gushchin <guro@fb.com> Reviewed-by: Randy Dunlap <rdunlap@infradead.org> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/vmscan.c')
-rw-r--r--mm/vmscan.c18
1 files changed, 17 insertions, 1 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 0e67b477ecef..03822f86f288 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2544,12 +2544,28 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
unsigned long reclaimed;
unsigned long scanned;
- if (mem_cgroup_low(root, memcg)) {
+ switch (mem_cgroup_protected(root, memcg)) {
+ case MEMCG_PROT_MIN:
+ /*
+ * Hard protection.
+ * If there is no reclaimable memory, OOM.
+ */
+ continue;
+ case MEMCG_PROT_LOW:
+ /*
+ * Soft protection.
+ * Respect the protection only as long as
+ * there is an unprotected supply
+ * of reclaimable memory from other cgroups.
+ */
if (!sc->memcg_low_reclaim) {
sc->memcg_low_skipped = 1;
continue;
}
memcg_memory_event(memcg, MEMCG_LOW);
+ break;
+ case MEMCG_PROT_NONE:
+ break;
}
reclaimed = sc->nr_reclaimed;