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From:   Shu Ming <sming56@gmail.com>
Date:   Mon, 22 Mar 2021 09:46:27 +0800
Message-ID: <CANt8P=vwbshvNntPLAkEQFrRfeSHfd1bkxLUhmRXNS2CD_mO_w@mail.gmail.com>
Subject: Re: [PATCH v4 1/3] mm/slub: Introduce two counters for partial objects
To:     Xunlei Pang <xlpang@linux.alibaba.com>
Cc:     Vlastimil Babka <vbabka@suse.cz>, 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>
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More precisely, ss will count partial objects like denty objects with
"/sys/kernel/slab/dentry/partial"   whose number can become huge.

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.