linux-kernel - Re: Excessive kernel time inside ttm when scrolling on a r700 in a multimonitor setup

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Message-ID: <CAH3drwanacWd_b_ZF3eNiDSijuG2tXgjt8BsgYYUb+pjAV09VA@mail.gmail.com>
Date:	Mon, 17 Sep 2012 05:59:34 -0400
From:	Jerome Glisse <j.glisse@...il.com>
To:	Andres Freund <andres@...razel.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	David Airlie <airlied@...ux.ie>,
	Jerome Glisse <jglisse@...hat.com>,
	Alex Deucher <alexander.deucher@....com>
Subject: Re: Excessive kernel time inside ttm when scrolling on a r700 in a
 multimonitor setup

On Mon, Sep 17, 2012 at 5:13 AM, Andres Freund <andres@...razel.de> wrote:
> On Monday, September 17, 2012 10:47:10 AM Jerome Glisse wrote:
>> On Sun, Sep 16, 2012 at 7:18 PM, Andres Freund <andres@...razel.de> wrote:
>> > Hi everyone,
>> >
>> > In several gui programs, most notably and reproducably, I can trivially
>> > make Xorg spend the whole cpu time in the kernel. It might be an Xorg
>> > bug, but from my untrained gut feeling it doesn't look that way.
>> >
>> > Anything more you need than whats already in the email?
>>
>> > Here are some details:
>> Is it an AGP card ? It looks like it's the PAT update that kills perf
>> for you, not much we can do, the pool allocator is probably starve.
> If you mean AGP as in the old strange graphics bus, no. Its a pcie card.
>
> If that helps you, more detailedly the card is a: SAPPHIRE Radeon HD6870
>
> Unfortunately the manufacturers page is remarkably devoid of details...:
> http://www.sapphiretech.com/presentation/product/?cid=1&gid=3&sgid=1037&lid=1&pid=1270&leg=0
>
> Greetings,
>
> Andres

Well, then the issue is that it tries to allocate write combined pages
on PCIE which should not happen. I don't see how in the code you endup
in that path unless drm_pci_device_is_agp return true for some
reasons.

Cheers,
Jerome
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