linux-kernel - Re: [RFT PATCH] blkio: alloc per cpu data from worker thread context( Re: kvm deadlock)

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Message-ID: <20111220204522.GI10752@google.com>
Date:	Tue, 20 Dec 2011 12:45:22 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	Nate Custer <nate@...nel.net>, Jens Axboe <axboe@...nel.dk>,
	Avi Kivity <avi@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>, kvm@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFT PATCH] blkio: alloc per cpu data from worker thread
 context( Re: kvm deadlock)

Hello,

On Tue, Dec 20, 2011 at 09:50:24AM -0500, Vivek Goyal wrote:
> So IIUC, existing mempool implementation is not directly usable for my
> requirement and I need to write some code of my own for the caching
> layer which always allocates objects from reserve and fills in the
> pool asynchronously with the help of a worker thread.

I've been looking at it and don't think allowing percpu allocator to
be called from no io path is a good idea.  The on-demand area filling
is tied into vmalloc area management which in turn is tied to arch
page table code and I really want to avoid pre-allocating full chunk -
it can be huge.  I'm trying to extend mempool to cover percpu areas,
so please wait a bit.

Thanks.

-- 
tejun
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