linux-kernel - Re: [PATCH] proc: Avoid a thundering herd of threads freeing proc dentries

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Message-ID: <87k1036k9y.fsf@x220.int.ebiederm.org>
Date:   Fri, 19 Jun 2020 12:24:41 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Junxiao Bi <junxiao.bi@...cle.com>
Cc:     Matthew Wilcox <willy@...radead.org>, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        Matthew Wilcox <matthew.wilcox@...cle.com>,
        Srinivas Eeda <SRINIVAS.EEDA@...cle.com>,
        "joe.jin\@oracle.com" <joe.jin@...cle.com>,
        Wengang Wang <wen.gang.wang@...cle.com>
Subject: Re: [PATCH] proc: Avoid a thundering herd of threads freeing proc dentries

Junxiao Bi <junxiao.bi@...cle.com> writes:

> Hi Eric,
>
> The patch didn't improve lock contention.

Which raises the question where is the lock contention coming from.

Especially with my first variant.  Only the last thread to be reaped
would free up anything in the cache.

Can you comment out the call to proc_flush_pid entirely?

That will rule out the proc_flush_pid in d_invalidate entirely.

The only candidate I can think of d_invalidate aka (proc_flush_pid) vs ps.

Eric