lkml.org 
[lkml]   [2008]   [Aug]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/4] AMD IOMMU: use status bit instead of memory write-back for completion wait
On Thu, Aug 14, 2008 at 08:35:30PM +0200, Ingo Oeser wrote:
> Hi Joerg,
>
> On Thursday 14 August 2008, Joerg Roedel wrote:
> > diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
> > index 22d7d05..028e945 100644
> > --- a/arch/x86/kernel/amd_iommu.c
> > +++ b/arch/x86/kernel/amd_iommu.c
> > @@ -122,9 +119,15 @@ static int iommu_completion_wait(struct amd_iommu *iommu)
> >
> > while (!ready && (i < EXIT_LOOP_COUNT)) {
> > ++i;
> > - cpu_relax();
>
> Could you elaborate, why you had to remove this?
>
> Busy waiting loops should always do cpu_relay()
> to reduce heat procution and power consumption while idle.

I removed it because its not idling anymore in that loop imho. It reads
data from MMIO and does a small calculation with it.

Joerg



\
 
 \ /
  Last update: 2008-08-14 22:05    [W:0.043 / U:1.484 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site