Date: Fri, 31 Oct 2008 08:16:44 +0100
From: Nick Piggin <npiggin@suse.de>
To: Glauber Costa <glommer@redhat.com>
Cc: Avi Kivity <avi@redhat.com>, linux-kernel@vger.kernel.org,
       kvm@vger.kernel.org, aliguori@codemonkey.ws,
       Jeremy Fitzhardinge <jeremy@goop.org>,
       Krzysztof Helt <krzysztof.h1@poczta.fm>
Subject: Re: [PATCH] regression: vmalloc easily fail.
Message-ID: <20081031071644.GD19268@wotan.suse.de>
References: <1225234513-3996-1-git-send-email-glommer@redhat.com> <20081028232944.GA3759@wotan.suse.de> <20081029094856.GD4269@poweredge.glommer> <20081029101145.GB5953@wotan.suse.de> <49083B14.6070402@redhat.com> <20081029104333.GD5953@wotan.suse.de> <20081029220737.GF11532@poweredge.glommer> <20081030044941.GA9470@wotan.suse.de> <20081030112854.GA18634@poweredge.glommer>
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On Thu, Oct 30, 2008 at 09:28:54AM -0200, Glauber Costa wrote:
> On Thu, Oct 30, 2008 at 05:49:41AM +0100, Nick Piggin wrote:
> > On Wed, Oct 29, 2008 at 08:07:37PM -0200, Glauber Costa wrote:
> > > On Wed, Oct 29, 2008 at 11:43:33AM +0100, Nick Piggin wrote:
> > > > On Wed, Oct 29, 2008 at 12:29:40PM +0200, Avi Kivity wrote:
> > > > > Nick Piggin wrote:
> > > > > >Hmm, spanning <30MB of memory... how much vmalloc space do you have?
> > > > > >
> > > > > >  
> > > > > 
> > > > > From the original report:
> > > > > 
> > > > > >VmallocTotal:     122880 kB
> > > > > >VmallocUsed:       15184 kB
> > > > > >VmallocChunk:      83764 kB
> > > > > 
> > > > > So it seems there's quite a bit of free space.
> > > > > 
> > > > > Chunk is the largest free contiguous region, right?  If so, it seems the 
> > > > 
> > > > Yes.
> > > > 
> > > > 
> > > > > problem is unrelated to guard pages, instead the search isn't finding a 
> > > > > 1-page area (with two guard pages) for some reason, even though lots of 
> > > > > free space is available.
> > > > 
> > > > Hmm. The free area search could be buggy...
> > > Do you want me to grab any specific info of it? Or should I just hack myself
> > > randomly into it? I'll probably have some time for that tomorrow.
> > 
> > I took a bit of a look. Does this help you at all?
> > 
> > I still think we should get rid of the guard pages in non-debug kernels
> > completely, but hopefully this will fix your problems?
> unfortunately, it doesn't.
> problem still happen in a kernel with this patch.

That's weird. Any chance you could dump a list of all the vmap area start
and end adresses and their flags before returning failure?


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