Why do you care about performance when PAT is disabled? Brice Goglin <brice.goglin at gmail.com> wrote:
>Le 21/06/2013 07:00, H. Peter Anvin a ?crit : >> An awful lot of drivers, mostly DRI drivers, are still mucking with >> MTRRs directly as opposed to using ioremap_wc() or similar >interfaces. >> In addition to the architecture dependency, this is really >undesirable >> because MTRRs are a limited resource, whereas page table attributes >are not. >> >> Furthermore, this perpetuates the need for the horrific hack known as >> "MTRR cleanup". >> >> What, if anything, can we do to clean up this mess? >> >> -hpa >> > >The first network driver that used ioremap_wc() back in 2008 (myri10ge) >had to keep using MTRR because ioremap_wc() silently falls back to >ioremap_nocache() when PAT is disabled. > >I asked about this in https://lkml.org/lkml/2008/5/31/42 and there was >some talk about putting the MTRR addition in the nocache fallback path >but I guess nobody implemented the idea. > >Brice -- Sent from my mobile phone. Please excuse brevity and lack of formatting.
