Re: [PATCH] Improve Atheros ethernet driver not to do order 4 GFP_ATOMIC allocation

[Chris Snook <chris.snook@gmail.com>]

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On Tue, Dec 1, 2015 at 12:35 PM David Miller <davem@davemloft.net> wrote:

> From: Michal Hocko <mhocko@kernel.org>
> Date: Mon, 30 Nov 2015 14:21:29 +0100
>
> > On Sat 28-11-15 15:51:13, Pavel Machek wrote:
> >>
> >> atl1c driver is doing order-4 allocation with GFP_ATOMIC
> >> priority. That often breaks  networking after resume. Switch to
> >> GFP_KERNEL. Still not ideal, but should be significantly better.
> >
> > It is not clear why GFP_KERNEL can replace GFP_ATOMIC safely neither
> > from the changelog nor from the patch context.
>
> Earlier in the function we do a GFP_KERNEL kmalloc so:
>
> ¯\_(ツ)_/¯
>
> It should be fine.
>

AFAICT, the people who benefit from GFP_ATOMIC are the people running all
their storage over NFS/iSCSI who are suspending their machines while
they're so busy they don't have any clean order 4 pagecache to drop, and
want the machine to panic rather than hang. The people who benefit from
GFP_KERNEL are the people who use their laptop for a while, put it to
sleep, and then wake it up again. I think the latter is the use case we
should be optimizing for.

-- Chris

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