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From: Shu Ming <sming56@gmail.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Xunlei Pang <xlpang@linux.alibaba.com>,
	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, 29 Mar 2021 09:58:52 +0800	[thread overview]
Message-ID: <CANt8P=uD1X4wMHeomCVmE2ggvTSn6h3H7Fcwmu-FrEqzgrtRiQ@mail.gmail.com> (raw)
In-Reply-To: <2ad0539f-2c38-714e-330e-7709bb07ebac@suse.cz>

I am not sure how people are using partial object accounting.  I
believe it is used as a memory usage hint of slabs.

On Mon, Mar 22, 2021 at 6:22 PM Vlastimil Babka <vbabka@suse.cz> wrote:
>
> 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.
> >
>


  reply	other threads:[~2021-03-29  1:59 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
2021-03-29  1:58           ` Shu Ming [this message]
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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