linux-kernel - Re: TTM page pool allocator

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Message-ID: <4A6764E0.7080302@shipmail.org>
Date:	Wed, 22 Jul 2009 21:13:36 +0200
From:	Thomas Hellström <thomas@...pmail.org>
To:	Jerome Glisse <glisse@...edesktop.org>
CC:	Michel Dänzer <michel@...nzer.net>,
	linux-kernel@...r.kernel.org, dri-devel@...ts.sf.net
Subject: Re: TTM page pool allocator

Jerome Glisse wrote:
> On Wed, 2009-07-22 at 15:16 +0200, Michel Dänzer wrote:
>   
>> On Tue, 2009-07-21 at 21:22 +0200, Jerome Glisse wrote:
>>     
>>> On Tue, 2009-07-21 at 20:00 +0200, Jerome Glisse wrote:
>>>       
>>>> On Tue, 2009-07-21 at 19:34 +0200, Jerome Glisse wrote:
>>>>         
>>>>> On Thu, 2009-06-25 at 17:53 +0200, Thomas Hellström wrote:
>>>>>           
>>>>>> 4) We could now skip the ttm_tt_populate() in ttm_tt_set_caching, since 
>>>>>> it will always allocate cached pages and then transition them.
>>>>>>
>>>>>>             
>>>>> Okay 4) is bad, what happens (my brain is a bit meltdown so i might be
>>>>> wrong) :
>>>>> 1 - bo get allocated tt->state = unpopulated
>>>>> 2 - bo is mapped few page are faulted tt->state = unpopulated
>>>>> 3 - bo is cache transitioned but tt->state == unpopulated but
>>>>>     they are page which have been touch by the cpu so we need
>>>>>     to clflush them and transition them, this never happen if
>>>>>     we don't call ttm_tt_populate and proceed with the remaining
>>>>>     of the cache transitioning functions
>>>>>
>>>>> As a workaround i will try to go through the pages tables and
>>>>> transition existing pages. Do you have any idea for a better
>>>>> plan ?
>>>>>
>>>>> Cheers,
>>>>> Jerome
>>>>>           
>>>> My workaround ruin the whole idea of pool allocation what happens
>>>> is that most bo get cache transition page per page. My thinking
>>>> is that we should do the following:
>>>> 	- is there is a least one page allocated then fully populate
>>>> 	the object and do cache transition on all the pages.
>>>> 	- otherwise update caching_state and leaves object unpopulated
>>>>
>>>> This needs that we some how reflect the fact that there is at least
>>>> one page allocated, i am thinking to adding a new state for that :
>>>> ttm_partialy_populated
>>>>
>>>> Thomas what do you think about that ?
>>>>
>>>> Cheers,
>>>> Jerome
>>>>         
>>> Attached updated patch it doesn't introduce ttm_partialy_populated
>>> but keep the populate call in cache transition. So far it seems to
>>> work properly on AGP platform
>>>       
>> Yeah, this one works for me as well.
>>
>>     
>>> and helps quite a lot with performances.
>>>       
>> Can't say I've noticed that however. How did you measure?
>>     
>
> gears 
Hmm,
In gears there shouldn't really be any buffer allocation / freeing going 
on at all once the display lists are set up, and gears should really be 
gpu bound in most cases.

what's the source of the buffer allocations / frees when gears is run?

/Thomas





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