Messages in this thread | | | Date | Thu, 14 Aug 2008 22:02:47 +0200 | From | Joerg Roedel <> | Subject | Re: [PATCH 1/4] AMD IOMMU: use status bit instead of memory write-back for completion wait |
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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
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