Re: [PATCH 08/17] bio: reimplement bio_copy_user_iov()

From: Tejun Heo
Date: Thu Apr 02 2009 - 03:51:37 EST


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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