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SubjectRe: TTM page pool allocator
Jerome Glisse wrote:
> On Thu, 2009-06-25 at 17:53 +0200, Thomas Hellström wrote:
>
>> Jerome Glisse skrev:
>>
>>> Hi,
>>>
>>> Thomas i attach a reworked page pool allocator based on Dave works,
>>> this one should be ok with ttm cache status tracking. It definitely
>>> helps on AGP system, now the bottleneck is in mesa vertex's dma
>>> allocation.
>>>
>>> Cheers,
>>> Jerome
>>>
>>>
>> Hi, Jerome!
>> In general it looks very good. Some things that need fixing:
>>
>> 1) We must have a way to hand back pages. I still not quite understand
>> how the shrink callbacks work and whether they are applicable. Another
>> scheme would be to free, say 1MB when we have at least 2MB available.
>>
>> 2) We should avoid including AGP headers if AGP is not configured.
>> Either reimplement unmap_page_from_agp or map_page_into_agp or move them
>> out from the AGP headers. We've hade complaints before from people with
>> AGP free systems that the code doesn't compile.
>>
>> 3) Since we're allocating (and freeing) in batches we should use the
>> set_pages_array() interface to avoid a global tlb flush per page.
>>
>> 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,

Right.

> this never happen if
> we don't call ttm_tt_populate and proceed with the remaining
> of the cache transitioning functions
>

Why can't we just skip ttm_tt_populate and proceed with the remaining of
the cache transitioning functions? Then all pages currently allocated to
the TTM will be transitioned.

/Thomas



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