linux-kernel - Re: [PATCH] regression: vmalloc easily fail.

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Message-ID: <20081105002149.GD27481@poweredge.glommer>
Date:	Tue, 4 Nov 2008 22:21:49 -0200
From:	Glauber Costa <glommer@...hat.com>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Avi Kivity <avi@...hat.com>, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, Jeremy Fitzhardinge <jeremy@...p.org>,
	Krzysztof Helt <krzysztof.h1@...zta.fm>
Subject: Re: [PATCH] regression: vmalloc easily fail.

On Fri, Oct 31, 2008 at 08:16:44AM +0100, Nick Piggin wrote:
> 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?

I said it worked with a single change. Shame on me, I was testing the wrong kernel
it does not work at all. I'll debug it more tomorrow.
> 
> 
> 
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