linux-kernel - Re: drm/nouneau: 5.11 cycle regression bisected to 461619f5c324 "drm/nouveau: switch to new allocator"

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Message-ID: <bfd62492-e6a9-3899-dd7d-87b7800f45c7@amd.com>
Date:   Wed, 10 Feb 2021 11:52:11 +0100
From:   Christian König <christian.koenig@....com>
To:     Mike Galbraith <efault@....de>, lkml <linux-kernel@...r.kernel.org>
Cc:     nouveau@...ts.freedesktop.org, Ben Skeggs <bskeggs@...hat.com>,
        Dave Airlie <airlied@...hat.com>
Subject: Re: drm/nouneau: 5.11 cycle regression bisected to 461619f5c324
 "drm/nouveau: switch to new allocator"

Am 10.02.21 um 11:46 schrieb Mike Galbraith:
> On Wed, 2021-02-10 at 11:34 +0100, Christian König wrote:
>> What seems to happen here is that your system is low on resources and we
>> just try to free up pages.
> FWIW, box has oodles generic ram free right after boot.

Then I have no idea what happens here.

The returned pages are identical, only the overhead to allocate them is 
reduced significantly.

The only other idea I have is that this somehow changes the timing and 
exposes a bug somewhere else.

You could try to replace the "for (order = min(MAX_ORDER - 1UL, 
__fls(num_pages)); num_pages;" in ttm_pool_alloc() with "for (order = 0; 
num_pages;" to get the old behavior.

Regards,
Christian.

>
> 	-Mike
>