From: Joerg Roedel <joro@8bytes.org>
To: Ingo Oeser <ioe-lkml@rameria.de>
Cc: Joerg Roedel <joerg.roedel@amd.com>,
mingo@redhat.com, tglx@linutronix.de, hpa@zytor.com,
linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org
Subject: Re: [PATCH 1/4] AMD IOMMU: use status bit instead of memory write-back for completion wait
Date: Thu, 14 Aug 2008 22:02:47 +0200 [thread overview]
Message-ID: <20080814200247.GA26988@8bytes.org> (raw)
In-Reply-To: <200808142035.32422.ioe-lkml@rameria.de>
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
next prev parent reply other threads:[~2008-08-14 20:02 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-14 17:55 [PATCH 0/4] AMD IOMMU updates for 2.6.27-rc3 Joerg Roedel
2008-08-14 17:55 ` [PATCH 1/4] AMD IOMMU: use status bit instead of memory write-back for completion wait Joerg Roedel
2008-08-14 18:35 ` Ingo Oeser
2008-08-14 20:02 ` Joerg Roedel [this message]
2008-08-14 17:55 ` [PATCH 2/4] AMD IOMMU: initialize device table properly Joerg Roedel
2008-08-14 17:55 ` [PATCH 3/4] AMD IOMMU: replace LOW_U32 macro with generic lower_32_bits Joerg Roedel
2008-08-14 17:55 ` [PATCH 4/4] AMD IOMMU: initialize dma_ops after sysfs registration Joerg Roedel
2008-08-15 11:57 ` [PATCH 0/4] AMD IOMMU updates for 2.6.27-rc3 Ingo Molnar
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