On 7/30/20 6:52 PM, Evgenii Shatokhin wrote:
> Hi,
>
> On 30.07.2020 18:02, Andrey Ryabinin wrote:
>> Exceeding cache above cache.limit_in_bytes schedules high_work_func()
>> which tries to reclaim 32 pages. If cache generated fast enough or it allows
>> cgroup to steadily grow above cache.limit_in_bytes because we don't reclaim
>> enough. Try to reclaim exceeded amount of cache instead.
>>
>> https://jira.sw.ru/browse/PSBM-106384
>> Signed-off-by: Andrey Ryabinin <aryabi...@virtuozzo.com>
>> ---
>>
>> - Changes since v1: add bug link to changelog
>> - Changes since v2: Fix cache_overused check (We should check if it's
>> positive).
>> Made this stupid bug during cleanup, patch was tested without bogus
>> cleanup,
>> so it shoud work.
>> - Chnages since v3: Compilation fixes, properly tested now.
>>
>> mm/memcontrol.c | 10 +++++++---
>> 1 file changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index 3cf200f506c3..16cbd451a588 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -3080,12 +3080,16 @@ static void reclaim_high(struct mem_cgroup *memcg,
>> {
>> do {
>> + long cache_overused;
>> +
>> if (page_counter_read(&memcg->memory) > memcg->high)
>> try_to_free_mem_cgroup_pages(memcg, nr_pages, gfp_mask, 0);
>> - if (page_counter_read(&memcg->cache) > memcg->cache.limit)
>> - try_to_free_mem_cgroup_pages(memcg, nr_pages, gfp_mask,
>> - MEM_CGROUP_RECLAIM_NOSWAP);
>> + cache_overused = page_counter_read(&memcg->cache) -
>> + memcg->cache.limit;
>
> If cache_overused is less than 32 pages, the kernel would try to reclaim less
> than before the patch. It it OK, or should it try to reclaim at least 32
> pages?
It's ok, try_to_free_mem_cgroup_pages will increase it:
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
unsigned long nr_pages,
gfp_t gfp_mask,
int flags)
....
.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
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