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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,


    > 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.


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