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

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Message-ID: <c7fcf5f6-b289-96a6-0e1b-0969254c0f22@oracle.com>
Date:   Mon, 22 Jun 2020 10:16:05 -0700
From:   Junxiao Bi <junxiao.bi@...cle.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.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@...cle.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

On 6/22/20 8:20 AM, ebiederm@...ssion.com wrote:

> If I understand correctly, the Java VM is not exiting.  Just some of
> it's threads.
>
> That is a very different problem to deal with.  That are many
> optimizations that are possible when_all_  of the threads are exiting
> that are not possible when_many_  threads are exiting.
>
> Do you know if it is simply the cpu time or if it is the lock contention
> that is the problem?  If it is simply the cpu time we should consider if
> some of the locks that can be highly contended should become mutexes.
> Or perhaps something like Matthew's cpu pinning idea.

The problem is high %sys time.

Thanks,

Junxiao.