Date: Tue, 7 Apr 2015 16:30:09 +0200
From: Michal Hocko <mhocko@suse.cz>
To: Ingo Molnar <mingo@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Sasha Levin <sasha.levin@oracle.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Rusty Russell <rusty@rustcorp.com.au>, Dave Jones <davej@redhat.com>,
        the arch/x86 maintainers <x86@kernel.org>
Subject: Re: Hang on large copy_from_user with PREEMPT_NONE
Message-ID: <20150407143009.GG7935@dhcp22.suse.cz>
References: <552204B8.40605@oracle.com>
 <CA+55aFztF9D1yK5zbbG9PiQufQU+6BX-hc4toDS_MHx4ieeYqQ@mail.gmail.com>
 <5522D9A8.5080104@oracle.com>
 <CA+55aFz8gByWhuAgW4fER8uw=q9E=tcN6LeS3YqCOqYsOfwPxA@mail.gmail.com>
 <20150407093145.GA10348@gmail.com>
 <20150407103955.GB14095@pd.tnic>
 <20150407110531.GA14136@gmail.com>
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On Tue 07-04-15 13:05:31, Ingo Molnar wrote:
> 
> * Borislav Petkov <bp@alien8.de> wrote:
> 
> > On Tue, Apr 07, 2015 at 11:31:45AM +0200, Ingo Molnar wrote:
> > > Would be nice to see the actual kernel .config, as there's a few
> > > debug features that can slow things down significantly, such as
> > > CONFIG_KMEMCHECK=y or in some cases CONFIG_DEBUG_PAGEALLOC=y.
> > 
> > He sent it here: https://lkml.kernel.org/r/55229D7E.6080309@oracle.com
> > 
> > I'm attaching it again.
> 
> Thanks. Nothing particularly expensive stands out to me at a quick 
> glance:-/

Sasha uses KASAN very often and it is enabled here as well. I guess this
might slow things really down.
-- 
Michal Hocko
SUSE Labs
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