From: Qi Zheng <zhengqi.arch@bytedance.com>
To: Roman Gushchin <roman.gushchin@linux.dev>
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: Tue, 28 Feb 2023 18:11:34 +0800 [thread overview]
Message-ID: <c949c89a-0b0d-723f-4c60-f6374b1993f3@bytedance.com> (raw)
In-Reply-To: <Y/z+P5cgeunD6u21@P9FQF9L96D>
On 2023/2/28 03:02, Roman Gushchin wrote:
> 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.
Yes, in the above scenario, there is indeed no lock contention problem.
>
> 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!
--
Thanks,
Qi
prev parent reply other threads:[~2023-02-28 10:11 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
2023-02-28 10:11 ` Qi Zheng [this message]
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