lkml.org 
[lkml]   [2012]   [Feb]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH 34/36] block: implement bio_associate_current()
Date
Tejun Heo <tj@kernel.org> writes:

> Hey, Jeff.

Hi, Tejun!

> On Wed, Feb 22, 2012 at 08:45:02AM -0500, Jeff Moyer wrote:
>> Tejun Heo <tj@kernel.org> writes:
>>
>> > -v2: #ifdef CONFIG_BLK_CGROUP added around bio->bi_ioc dereference in
>> > rq_ioc() to fix build breakage.
>>
>> This is useful for cfq without blk cgroups as well, right? Why have you
>> limited the scope like this?
>
> Because blk-throttle is the only current user. We can move the
> BLK_CGROUP to cover just bi_css later on as we add more users.

I guess you're going to make me read the whole patch set. ;-) What I'm
getting at is CFQ uses the io_context to make its scheduling decisions.
If we can propagate the issuer's I/O context from bio creation all the
way down to the I/O scheduler, then we can do a better job of accounting
I/O (and hence scheduling, preemption, etc). As Vivek mentioned
previously, we have seen performance issues with the dm-crypt target and
CFQ, precisely because all of the I/O is submitted in the context of a
worker thread, and the the process that initiated the I/O is unknown at
that point.

Hopefully I've either cleared up my question, or proven to you that I do
need to go read the rest of the patch set to understand why my question
doesn't make sense. Let me know which is the case. ;-)

Cheers,
Jeff


\
 
 \ /
  Last update: 2012-02-22 20:37    [W:0.090 / U:0.032 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site