linux-kernel - Re: [PATCH 34/36] block: implement bio_associate

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 22 Feb 2012 14:33:43 -0500
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	axboe@...nel.dk, vgoyal@...hat.com, ctalbott@...gle.com,
	rni@...gle.com, linux-kernel@...r.kernel.org,
	Kent Overstreet <koverstreet@...gle.com>
Subject: Re: [PATCH 34/36] block: implement bio_associate_current()

Tejun Heo <tj@...nel.org> writes:

> Hey, Jeff.

Hi, Tejun!

> On Wed, Feb 22, 2012 at 08:45:02AM -0500, Jeff Moyer wrote:
>> Tejun Heo <tj@...nel.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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/