Re: [Bug 10328] New: [regression] performance drop for glx

Ingo Molnar
2008-03-26T05:29:49Z

* Suresh Siddha <suresh.b.siddha@intel.com> wrote:

> fb drivers are using ioremap()/ioremap_nocache(), followed by mtrr_add
> with WC attribute. Recent changes in page attribute code made both
> ioremap()/ioremap_nocache() mappings as UC (instead of previous UC-).
> This breaks the graphics performance, as the effective memory type is
> UC instead of expected WC.
>
> The correct way to fix this is to add ioremap_wc() (which uses UC- in
> the absence of PAT kernel support and WC with PAT) and change all the
> fb drivers to use this new ioremap_wc() API.
>
> We can take this correct and longer route for post 2.6.25. For now,
> revert back to the UC- behavior for ioremap/ioremap_nocache.

thanks Suresh, applied.

Ingo