From: Vlastimil Babka <vbabka@suse.cz>
To: Shu Ming <sming56@gmail.com>, Xunlei Pang <xlpang@linux.alibaba.com>
Cc: Christoph Lameter <cl@linux.com>,
Christoph Lameter <cl@gentwo.de>,
Pekka Enberg <penberg@kernel.org>, Roman Gushchin <guro@fb.com>,
Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
David Rientjes <rientjes@google.com>,
Matthew Wilcox <willy@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org, Wen Yang <wenyang@linux.alibaba.com>,
James Wang <jnwang@linux.alibaba.com>
Subject: Re: [PATCH v4 1/3] mm/slub: Introduce two counters for partial objects
Date: Mon, 22 Mar 2021 11:22:43 +0100 [thread overview]
Message-ID: <2ad0539f-2c38-714e-330e-7709bb07ebac@suse.cz> (raw)
In-Reply-To: <CANt8P=vwbshvNntPLAkEQFrRfeSHfd1bkxLUhmRXNS2CD_mO_w@mail.gmail.com>
On 3/22/21 2:46 AM, Shu Ming wrote:
> More precisely, ss will count partial objects like denty objects with
> "/sys/kernel/slab/dentry/partial" whose number can become huge.
Uh, that's interesting. Would you know what exactly it uses the value for? I can
think of several reasons why it might be misleading.
> On Thu, Mar 18, 2021 at 8:56 PM Xunlei Pang <xlpang@linux.alibaba.com> wrote:
>>
>>
>>
>> On 3/18/21 8:18 PM, Vlastimil Babka wrote:
>> > On 3/17/21 8:54 AM, Xunlei Pang wrote:
>> >> The node list_lock in count_partial() spends long time iterating
>> >> in case of large amount of partial page lists, which can cause
>> >> thunder herd effect to the list_lock contention.
>> >>
>> >> We have HSF RT(High-speed Service Framework Response-Time) monitors,
>> >> the RT figures fluctuated randomly, then we deployed a tool detecting
>> >> "irq off" and "preempt off" to dump the culprit's calltrace, capturing
>> >> the list_lock cost nearly 100ms with irq off issued by "ss", this also
>> >> caused network timeouts.
>> >
>> > I forgot to ask, how does "ss" come into this? It displays network connections
>> > AFAIK. Does it read any SLUB counters or slabinfo?
>> >
>>
>> ss may access /proc/slabinfo to acquire network related slab statistics.
>
next prev parent reply other threads:[~2021-03-22 10:23 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-17 7:54 [PATCH v4 0/3] mm/slub: Fix count_partial() problem Xunlei Pang
2021-03-17 7:54 ` [PATCH v4 1/3] mm/slub: Introduce two counters for partial objects Xunlei Pang
2021-03-17 18:45 ` Vlastimil Babka
2021-03-18 4:52 ` Xunlei Pang
2021-03-18 12:18 ` Vlastimil Babka
2021-03-18 12:56 ` Xunlei Pang
2021-03-22 1:46 ` Shu Ming
2021-03-22 10:22 ` Vlastimil Babka [this message]
2021-03-29 1:58 ` Shu Ming
2021-03-17 7:54 ` [PATCH v4 2/3] percpu: Export per_cpu_sum() Xunlei Pang
2021-03-17 7:54 ` [PATCH v4 3/3] mm/slub: Get rid of count_partial() Xunlei Pang
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