Messages in this thread | | | Date | Wed, 16 Apr 2008 15:18:17 -0700 | From | Suresh Siddha <> | Subject | Re: [v2.6.26] what's brewing in x86.git for v2.6.26 |
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On Wed, Apr 16, 2008 at 01:37:30PM -0700, Roland Dreier wrote: > > - PAT support - first step towards phasing out MTRR's for cache > > attribute control > > I just grabbed your tree and I see that there is no > pgprot_writecombine() for x86. I see that pci_mmap_page_range() handles > write combining but there's no way for a PCI driver to allow userspace > to mmap() part of a BAR with WC enabled. Doing this gives a big > performance boost for running low-latency apps on InfiniBand hardware > driven by the mlx4 driver (look for the FIXME about it in > drivers/infiniband/hw/mlx4/main.c). Are there any plans to handle this > somehow?
Yes. We are planning to fix this by tracking the attribute usage specified in the pgprot field of remap_pfn_range(). Once the attribute is tracked properly, we can add pgprot_writecombine() for WC case.
This should also help the other drivers like video fb etc which specify the UC/WC attribute for user level mmap.
thanks, suresh
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