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    SubjectRe: TTM page pool allocator
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    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, 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

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