From: "Christian König" <ckoenig.leichtzumerken@gmail.com>
To: Chris Wilson <chris@chris-wilson.co.uk>, Daniel Vetter <daniel@ffwll.ch>
Cc: "Kempczynski, Zbigniew" <zbigniew.kempczynski@intel.com>,
Andi Shyti <andi.shyti@intel.com>,
dri-devel <dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH] drm/mm: revert "Break long searches in fragmented address spaces"
Date: Wed, 1 Apr 2020 09:29:34 +0200 [thread overview]
Message-ID: <547dca13-bd62-9319-ee44-6894ee1b60af@gmail.com> (raw)
In-Reply-To: <158566075049.18289.17918401274396829066@build.alporthouse.com>
Am 31.03.20 um 15:19 schrieb Chris Wilson:
> 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.
Wow, that is indeed quite a lot.
What is the criteria use for ordering the tree? Just the size or is that
size+alignment?
Never looked into this, but maybe we have a low hanging fruit for an
improvement here?
I'm not 100% sure, but moving away from atomic context wouldn't be that
easy.
Christian.
> -Chris
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next prev parent reply other threads:[~2020-04-01 7:29 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
2020-04-01 7:29 ` Christian König [this message]
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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