From: Chris Wilson <chris@chris-wilson.co.uk>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: Andi Shyti <andi.shyti@intel.com>,
Christian König <ckoenig.leichtzumerken@gmail.com>,
dri-devel <dri-devel@lists.freedesktop.org>,
"Kempczynski, Zbigniew" <zbigniew.kempczynski@intel.com>
Subject: Re: [PATCH] drm/mm: revert "Break long searches in fragmented address spaces"
Date: Tue, 31 Mar 2020 14:19:10 +0100 [thread overview]
Message-ID: <158566075049.18289.17918401274396829066@build.alporthouse.com> (raw)
In-Reply-To: <CAKMK7uGNxhZB9Fd3i7rGK42pAgoJACRoR_NrrXF6rfCFkrg4GQ@mail.gmail.com>
Quoting Daniel Vetter (2020-03-31 11:38:50)
> On Tue, Mar 31, 2020 at 11:20 AM Chris Wilson <chris@chris-wilson.co.uk> wrote:
> > Quoting Daniel Vetter (2020-03-31 10:16:18)
> > > On Tue, Mar 31, 2020 at 10:59:45AM +0200, Christian König wrote:
> > > > A not so gentle ping, since this pretty much broke all TTM based drivers.
> > > >
> > > > Could we revert this for now?
> > >
> > > Always ack for revert.
> > >
> > > Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> >
> > So you didn't check the earlier patch either?
>
> I did, but wasn't super sold on the idea of more flags to smack an r-b
> onto it, so figured I'll throw the default ack-for-revert on this
> meanwhile.
We allow userspace to poison the drm_mm at roughly 8K intervals, a
search space of 35b with typically O(N^2) behaviour and each node
traversal (rb_next/rb_prev) will itself be costly. Even our simple tests
can generate a search of several minutes before our patience runs out.o
Any drm_mm that allows for userspace to control alignment can be
arbitrarily fragmented, hence a raised eyebrow that this search would be
allowed in atomic context.
-Chris
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next prev parent reply other threads:[~2020-03-31 13:19 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-30 12:34 [PATCH] drm/mm: revert "Break long searches in fragmented address spaces" Christian König
2020-03-30 12:40 ` Chris Wilson
2020-03-31 8:59 ` Christian König
2020-03-31 9:16 ` Daniel Vetter
2020-03-31 9:20 ` Chris Wilson
2020-03-31 10:38 ` Daniel Vetter
2020-03-31 12:44 ` Christian König
2020-03-31 13:19 ` Chris Wilson [this message]
2020-04-01 7:29 ` Christian König
2020-04-01 8:53 ` Chris Wilson
2020-04-01 9:17 ` Christian König
2020-04-06 8:25 ` Christian König
2020-03-31 9:19 ` Chris Wilson
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