linux-kernel - Re: [PATCH 5/8] cfq-iosched: remove @gfp_mask from cfq_find_alloc

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Message-ID: <x493821t0oi.fsf@segfault.boston.devel.redhat.com>
Date:	Tue, 09 Jun 2015 10:29:33 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	axboe@...nel.dk, linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org, vgoyal@...hat.com,
	avanzini.arianna@...il.com
Subject: Re: [PATCH 5/8] cfq-iosched: remove @gfp_mask from cfq_find_alloc_queue()

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

> Hey, Jeff.
>
> On Mon, Jun 08, 2015 at 04:27:10PM -0400, Jeff Moyer wrote:
>> >> Remove @gfp_mask from cfq_find_alloc_queue() and propagate the changes
>> >> to its callers.  This simplifies the function quite a bit and will
>> >> help making async queues per-cfq_group.
>> >
>> > Sorry, I disagree with this patch.  You've changed it so that all cfqq
>> > allocations are GFP_ATOMIC, and most, if not all of them simply don't
>> > need to be.
>> 
>> It occurs to me that replacing GFP_ATOMIC with GFP_NOWAIT in your patch
>> would address my concerns, and patches 6-8 would apply almost as-is.
>> What do you think about that?
>
> Oh yeah, it's okay to fail these allocations under memory pressure.
> GFP_NOWAIT is the better pick here.  It's GFP_ATOMIC mostly due to
> historic copy&paste anyway.  I'll change them to GFP_NOWAIT.

OK.  Assuming that's the only change, you can go ahead and add my
Reviewed-by: Jeff Moyer <jmoyer@...hat.com> to the next iteration.

Thanks!
Jeff
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