[Devel] [PATCH rh7 v4] mm/memcg: fix cache growth above cache.limit_in_bytes

[Konstantin Khorenko]

Andrey, please port fixes for memcg.cache.limit_in_bytes feature to vz8 as well.

AFAIS, the initial patch has been committed to vz8 already:
vz8: 0d64967242fd mm/memcg: limit page cache in memcg hack

But vz7 has several more fixes for it, which are to be ported yet:
vz7: 1bfd6445b3f29f503d9693254826283a8be65cfe mm/memcg: reclaim memory.cache.limit_in_bytes from background
vz7: 7e96384c9557dc9bd2525a2afb95630c866c7090 mm/memcg: fix cache growth above cache.limit_in_bytes
vz7: d7bab0af6a65 mm: try harder to decrease cache.limit_in_bytes

Thank you.

--
Best regards,

Konstantin Khorenko,
Virtuozzo Linux Kernel Team

On 07/30/2020 06:02 PM, 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 <aryabinin at 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 > 0)
> +			try_to_free_mem_cgroup_pages(memcg, cache_overused,
> +					gfp_mask, MEM_CGROUP_RECLAIM_NOSWAP);
>
>  	} while ((memcg = parent_mem_cgroup(memcg)));
>  }
>