linux-kernel - Re: [PATCH 08/17] bio: reimplement bio_copy_user

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Message-ID: <49D46E72.7030301@kernel.org>
Date:	Thu, 02 Apr 2009 16:51:14 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Boaz Harrosh <bharrosh@...asas.com>
CC:	axboe@...nel.dk, linux-kernel@...r.kernel.org,
	fujita.tomonori@....ntt.co.jp
Subject: Re: [PATCH 08/17] bio: reimplement bio_copy_user_iov()

Boaz Harrosh wrote:
> On 04/02/2009 04:38 AM, Tejun Heo wrote:
>> Hello, Boaz.
>>
>> Boaz Harrosh wrote:
>>> Please consider that this code-path is used by me, in exofs and
>>> pNFS-objcets in a very very hot path, where memory pressure is a
>>> common scenario.
>> One quick question.  Don't the above paths map kernel pages to a
>> request?
>>
> 
> Well vfs-page-cache pages. Any ideas?

In that case it would go through blk_rq_map_kern_sg(), so unless you
wanna change the blk_rq_map_kern_sg() interface such that it uses
bvec, the sgl overhead doesn't matter anyway.  Of course, if it has
been buidling bios directly, that is a different story.

Thanks.

-- 
tejun
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