From: Roman Gushchin <roman.gushchin@linux.dev>
To: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
tkhai@ya.ru, hannes@cmpxchg.org, shakeelb@google.com,
mhocko@kernel.org, muchun.song@linux.dev, david@redhat.com,
shy828301@gmail.com, sultan@kerneltoast.com, dave@stgolabs.net,
penguin-kernel@I-love.SAKURA.ne.jp, paulmck@kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 0/8] make slab shrink lockless
Date: Mon, 27 Feb 2023 11:02:23 -0800 [thread overview]
Message-ID: <Y/z+P5cgeunD6u21@P9FQF9L96D> (raw)
In-Reply-To: <b7e8929c-8fd5-a248-f8a8-d9177fc01b4b@bytedance.com>
On Mon, Feb 27, 2023 at 09:31:51PM +0800, Qi Zheng wrote:
>
>
> On 2023/2/27 03:51, Andrew Morton wrote:
> > On Sun, 26 Feb 2023 22:46:47 +0800 Qi Zheng <zhengqi.arch@bytedance.com> wrote:
> >
> Save the above script, then run test and touch commands.
>
> Then we can use the following perf command to view hotspots:
>
> perf top -U -F 999
>
> 1) Before applying this patchset:
>
> 32.31% [kernel] [k] down_read_trylock
> 19.40% [kernel] [k] pv_native_safe_halt
> 16.24% [kernel] [k] up_read
> 15.70% [kernel] [k] shrink_slab
> 4.69% [kernel] [k] _find_next_bit
> 2.62% [kernel] [k] shrink_node
> 1.78% [kernel] [k] shrink_lruvec
> 0.76% [kernel] [k] do_shrink_slab
>
> 2) After applying this patchset:
>
> 27.83% [kernel] [k] _find_next_bit
> 16.97% [kernel] [k] shrink_slab
> 15.82% [kernel] [k] pv_native_safe_halt
> 9.58% [kernel] [k] shrink_node
> 8.31% [kernel] [k] shrink_lruvec
> 5.64% [kernel] [k] do_shrink_slab
> 3.88% [kernel] [k] mem_cgroup_iter
Not opposing the intention of the patchset in any way (I actually think
it's a good idea to make the shrinkers list lockless), but looking at
both outputs above I think that the main problem is not the contention on
the semaphore, but the reason of this contention.
It seems like often there is a long list of shrinkers which barely
can reclaim any memory, but we're calling them again and again.
In order to achieve real wins with real-life workloads, I guess
it's what we should optimize.
Thanks!
next prev parent reply other threads:[~2023-02-27 19:02 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-26 14:46 Qi Zheng
2023-02-26 14:46 ` [PATCH v3 1/8] mm: vmscan: add a map_nr_max field to shrinker_info Qi Zheng
2023-02-26 14:54 ` Qi Zheng
2023-02-26 14:46 ` [PATCH v3 2/8] mm: vmscan: make global slab shrink lockless Qi Zheng
2023-02-26 14:46 ` [PATCH v3 3/8] mm: vmscan: make memcg " Qi Zheng
2023-02-26 14:46 ` [PATCH v3 4/8] mm: vmscan: add shrinker_srcu_generation Qi Zheng
2023-02-26 14:46 ` [PATCH v3 5/8] mm: shrinkers: make count and scan in shrinker debugfs lockless Qi Zheng
2023-02-26 14:46 ` [PATCH v3 6/8] mm: vmscan: hold write lock to reparent shrinker nr_deferred Qi Zheng
2023-02-26 14:46 ` [PATCH v3 7/8] mm: vmscan: remove shrinker_rwsem from synchronize_shrinkers() Qi Zheng
2023-02-26 14:46 ` [PATCH v3 8/8] mm: shrinkers: convert shrinker_rwsem to mutex Qi Zheng
2023-02-26 19:51 ` [PATCH v3 0/8] make slab shrink lockless Andrew Morton
2023-02-27 13:31 ` Qi Zheng
2023-02-27 15:08 ` Mike Rapoport
2023-02-27 19:20 ` Kirill Tkhai
2023-02-27 19:32 ` Roman Gushchin
2023-02-27 19:47 ` Kirill Tkhai
2023-02-28 10:08 ` Qi Zheng
2023-02-28 10:04 ` Qi Zheng
2023-02-28 10:53 ` Qi Zheng
2023-02-28 18:40 ` Michal Hocko
2023-03-01 2:27 ` Qi Zheng
2023-02-27 19:02 ` Roman Gushchin [this message]
2023-02-28 10:11 ` Qi Zheng
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Y/z+P5cgeunD6u21@P9FQF9L96D \
--to=roman.gushchin@linux.dev \
--cc=akpm@linux-foundation.org \
--cc=dave@stgolabs.net \
--cc=david@redhat.com \
--cc=hannes@cmpxchg.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@kernel.org \
--cc=muchun.song@linux.dev \
--cc=paulmck@kernel.org \
--cc=penguin-kernel@I-love.SAKURA.ne.jp \
--cc=shakeelb@google.com \
--cc=shy828301@gmail.com \
--cc=sultan@kerneltoast.com \
--cc=tkhai@ya.ru \
--cc=zhengqi.arch@bytedance.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox