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

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Date:	Tue, 9 Jun 2015 12:00:54 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Jeff Moyer <jmoyer@...hat.com>
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()

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.

Thanks.

-- 
tejun
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