Re: [PATCH 5/8] cfq-iosched: remove @gfp_mask from cfq_find_alloc_queue()

From: Tejun Heo
Date: Mon Jun 08 2015 - 23:01:41 EST


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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