[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <ZdOtEgwuwDTtVw3L@tiehlicka>
Date: Mon, 19 Feb 2024 20:33:38 +0100
From: Michal Hocko <mhocko@...e.com>
To: "T.J. Mercier" <tjmercier@...gle.com>
Cc: Johannes Weiner <hannes@...xchg.org>,
Roman Gushchin <roman.gushchin@...ux.dev>,
Shakeel Butt <shakeelb@...gle.com>,
Muchun Song <muchun.song@...ux.dev>,
Andrew Morton <akpm@...ux-foundation.org>,
Efly Young <yangyifei03@...ishou.com>, android-mm@...gle.com,
yuzhao@...gle.com, mkoutny@...e.com,
Yosry Ahmed <yosryahmed@...gle.com>, cgroups@...r.kernel.org,
linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] mm: memcg: Use larger batches for proactive reclaim
On Tue 06-02-24 17:52:50, T.J. Mercier wrote:
> Before 388536ac291 ("mm:vmscan: fix inaccurate reclaim during proactive
> reclaim") we passed the number of pages for the reclaim request directly
> to try_to_free_mem_cgroup_pages, which could lead to significant
> overreclaim. After 0388536ac291 the number of pages was limited to a
> maximum 32 (SWAP_CLUSTER_MAX) to reduce the amount of overreclaim.
> However such a small batch size caused a regression in reclaim
> performance due to many more reclaim start/stop cycles inside
> memory_reclaim. The restart cost is amortized over more pages with
> larger batch sizes, and becomes a significant component of the runtime
> if the batch size is too small.
>
> Reclaim tries to balance nr_to_reclaim fidelity with fairness across
> nodes and cgroups over which the pages are spread. As such, the bigger
> the request, the bigger the absolute overreclaim error. Historic
> in-kernel users of reclaim have used fixed, small sized requests to
> approach an appropriate reclaim rate over time. When we reclaim a user
> request of arbitrary size, use decaying batch sizes to manage error while
> maintaining reasonable throughput.
>
> MGLRU enabled - memcg LRU used
> root - full reclaim pages/sec time (sec)
> pre-0388536ac291 : 68047 10.46
> post-0388536ac291 : 13742 inf
> (reclaim-reclaimed)/4 : 67352 10.51
>
> MGLRU enabled - memcg LRU not used
> /uid_0 - 1G reclaim pages/sec time (sec) overreclaim (MiB)
> pre-0388536ac291 : 258822 1.12 107.8
> post-0388536ac291 : 105174 2.49 3.5
> (reclaim-reclaimed)/4 : 233396 1.12 -7.4
>
> MGLRU enabled - memcg LRU not used
> /uid_0 - full reclaim pages/sec time (sec)
> pre-0388536ac291 : 72334 7.09
> post-0388536ac291 : 38105 14.45
> (reclaim-reclaimed)/4 : 72914 6.96
>
> Fixes: 0388536ac291 ("mm:vmscan: fix inaccurate reclaim during proactive reclaim")
> Signed-off-by: T.J. Mercier <tjmercier@...gle.com>
> Reviewed-by: Yosry Ahmed <yosryahmed@...gle.com>
> Acked-by: Johannes Weiner <hannes@...xchg.org>
> Acked-by: Shakeel Butt <shakeelb@...gle.com>
> Reviewed-by: Michal Koutný <mkoutny@...e.com>
Acked-by: Michal Hocko <mhocko@...e.com>
Sorry, I've missed this version
--
Michal Hocko
SUSE Labs
Powered by blists - more mailing lists