Re: TTM page pool allocator

[Thomas HellstrÃm]

Jerome Glisse wrote:
> On Thu, 2009-06-25 at 17:53 +0200, Thomas HellstrÃm 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



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/