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From: Tejun Heo <tj@kernel.org>
To: David Miller <davem@davemloft.net>
Cc: linux-kernel@vger.kernel.org
Subject: Re: More problems in setup_pcpu_remap()
Date: Thu, 02 Apr 2009 13:42:57 +0900	[thread overview]
Message-ID: <49D44251.4000606@kernel.org> (raw)
In-Reply-To: <20090401.213112.96144152.davem@davemloft.net>

Hello,

David Miller wrote:
> The way this code is currently designed, it can exhaust all of the
> VMALLOC address space on both x86 and x86_64, and then some.
> 
> It allocates PMD_SIZE * num_possible_cpus() of vmalloc space.
> 
> PMD_SIZE is 2MB, num_possible_cpus() can be up to 4096....
> which can easily exceed (VMALLOC_END - VMALLOC_START)
> 
> Initially I had set out to implement sparc64 support for the new
> per-cpu stuff, but it looks like I'm stuck finding bugs in the x86
> implementation instead :-)

Eh... sorry about that.  :-)

I guess we'll have to put a cap on how high possible cpus can be for
remap allocator.  e.g. if single chunk size is over 20% of the whole
vmalloc area, don't use remap.  Does anyone have a good random %
number on mind?

Thanks.

-- 
tejun

  reply	other threads:[~2009-04-02  4:43 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-04-02  4:31 More problems in setup_pcpu_remap() David Miller
2009-04-02  4:42 ` Tejun Heo [this message]
2009-04-02  4:52   ` David Miller
2009-04-02  5:55     ` Tejun Heo
2009-04-02  7:07       ` David Miller
2009-04-02  7:22         ` Tejun Heo

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