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From: ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman)
To: cool linux <linux.cool.hot-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
Subject: Re: why this behavior in 3.16 kernel ?
Date: Thu, 04 Aug 2016 09:15:29 -0500	[thread overview]
Message-ID: <87h9b062ny.fsf@x220.int.ebiederm.org> (raw)
In-Reply-To: <CAJ5w2C=u_sNP4-ZHm1HH=stU-8ngbPDFuY7JimWqYPesPajkMg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> (cool linux's message of "Thu, 4 Aug 2016 12:49:36 +0530")

cool linux <linux.cool.hot-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> writes:

> Hi Eric/Andrew,
>
> Thanks for your response.
>
> I have commented out the synchronize_rcu() in namespace_unlock() which is
> located in /fs/namespace.c namespace_unlock() 
>
> now am able to see the result in fraction of seconds.

Interesting.   So it is just the fact you are serializing things in the
loop that makes things slow.

I would recommend syncrhonize_rcu_expidited but in this case since we
aren't holding a lock this is a case that looks like it will only show
up when testing (because things are needlessly serialized) and not in
the real world.

Eric

      parent reply	other threads:[~2016-08-04 14:15 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-08-03 11:08 why this behavior in 3.16 kernel ? cool linux
     [not found] ` <CAJ5w2CmDcXzOKppojwN2F5H-mFu_OM-XUoTWnTuLKrdoPG9iQg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-08-03 17:48   ` Eric W. Biederman
     [not found]     ` <877fbxhhfi.fsf-JOvCrm2gF+uungPnsOpG7nhyD016LWXt@public.gmane.org>
2016-08-04  1:14       ` Andrew Vagin
     [not found]         ` <20160804011401.GA20044-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2016-08-04  6:21           ` Andrew Vagin
     [not found]             ` <20160804062150.GB14503-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2016-08-04  7:19               ` cool linux
     [not found]                 ` <CAJ5w2C=u_sNP4-ZHm1HH=stU-8ngbPDFuY7JimWqYPesPajkMg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-08-04 14:15                   ` Eric W. Biederman [this message]

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