linux-kernel - Re: sparc64 pcpu failures...

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Message-Id: <20090917.223723.07032792.davem@davemloft.net>
Date:	Thu, 17 Sep 2009 22:37:23 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	tj@...nel.org
Cc:	linux-kernel@...r.kernel.org
Subject: Re: sparc64 pcpu failures...

From: David Miller <davem@...emloft.net>
Date: Thu, 17 Sep 2009 22:18:07 -0700 (PDT)

> 
> Tejun, I just started seeing the following on sparc64:
> 
> [   56.422005] WARNING: at mm/vmalloc.c:1991 pcpu_get_vm_areas+0x1b4/0x5fc()
 ...
> Might this be a result of:
> 
> commit bcb2107fdbecef3de55d597d23453747af81ba88
> Author: Tejun Heo <tj@...nel.org>
> Date:   Fri Aug 14 15:00:53 2009 +0900
> 
>     sparc64: use embedding percpu first chunk allocator
>     
>     sparc64 currently allocates a large page for each cpu and partially
>     remap them into vmalloc area much like what lpage first chunk
>     allocator did.  As a 4M page is used for each cpu, this results in
>     very large unit size and also adds TLB pressure due to the double
>     mapping of pages in the first chunk.
>     
>     This patch converts sparc64 to use the embedding percpu first chunk
>     allocator which now knows how to handle NUMA configurations.  This
>     simplifies the code a lot, doesn't incur any extra TLB pressure and
>     results in better utilization of address space.
>     
>     Signed-off-by: Tejun Heo <tj@...nel.org>
>     Acked-by: David S. Miller <davem@...emloft.net>
> 
> Do you think?

I've verified that reverting this makes the problem go away.
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