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Date: Thu, 20 Jan 2011 12:19:27 +0100
From: Tejun Heo <tj@kernel.org>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>, Pekka Enberg <penberg@kernel.org>,
        Ingo Molnar <mingo@elte.hu>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: percpu related boot crash on x86
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Hello,

On Thu, Jan 20, 2011 at 12:12:47PM +0100, Eric Dumazet wrote:
> Le jeudi 20 janvier 2011 à 11:47 +0100, Peter Zijlstra a écrit :
> > On Thu, 2011-01-20 at 10:31 +0200, Pekka Enberg wrote:
> > >    if (!irqs_disabled())
> > > 
> > > guard around the debugging code to make vfree() always work with IRQs 
> > > disabled. 
> > 
> > That won't be sufficient, __purge_vmap_area_lazy() needs to call
> > flush_tlb_kernel_range() occasionally.
> > 
> > There really is a good reason vmalloc()/vfree() don't work with
> > interrupts disabled.
> 
> Hmm, I would try to increase PERCPU_DYNAMIC_RESERVE, or pcpu_mem_alloc()
> could try to use kzalloc() even for allocations bigger than one PAGE,
> and fallback to vzalloc().

It already handles all those stuff.  As I wrote in the other message,
I don't think this problem has much to do with percpu allocator
itself.

> We have more alloc_percpu() uses, we also should try to use first chunk
> if possible.

Yeah, but that's true.  It's probably too small at this point.  Maybe
there should be a way to monitor percpu memory status, a proc entry or
something so that we can have more data on sizing.

Thanks.

-- 
tejun