From: Will Deacon <will@kernel.org>
To: John Garry <john.garry@huawei.com>
Cc: trivial@kernel.org, maz@kernel.org, linux-kernel@vger.kernel.org,
linuxarm@huawei.com, iommu@lists.linux-foundation.org,
robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 0/4] iommu/arm-smmu-v3: Improve cmdq lock efficiency
Date: Thu, 16 Jul 2020 11:22:33 +0100 [thread overview]
Message-ID: <20200716102233.GC7036@willie-the-truck> (raw)
In-Reply-To: <20200716101940.GA7036@willie-the-truck>
On Thu, Jul 16, 2020 at 11:19:41AM +0100, Will Deacon wrote:
> On Tue, Jun 23, 2020 at 01:28:36AM +0800, John Garry wrote:
> > As mentioned in [0], the CPU may consume many cycles processing
> > arm_smmu_cmdq_issue_cmdlist(). One issue we find is the cmpxchg() loop to
> > get space on the queue takes approx 25% of the cycles for this function.
> >
> > This series removes that cmpxchg().
>
> How about something much simpler like the diff below?
Ah, scratch that, I don't drop the lock if we fail the cas with it held.
Let me hack it some more (I have no hardware so I can only build-test this).
Will
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next prev parent reply other threads:[~2020-07-16 10:22 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-22 17:28 [PATCH 0/4] iommu/arm-smmu-v3: Improve cmdq lock efficiency John Garry
2020-06-22 17:28 ` [PATCH 1/4] iommu/arm-smmu-v3: Fix trivial typo John Garry
2020-06-22 17:28 ` [PATCH 2/4] iommu/arm-smmu-v3: Calculate bits for prod and owner John Garry
2020-06-22 17:28 ` [PATCH 3/4] iommu/arm-smmu-v3: Always issue a CMD_SYNC per batch John Garry
2020-06-22 17:28 ` [PATCH 4/4] iommu/arm-smmu-v3: Remove cmpxchg() in arm_smmu_cmdq_issue_cmdlist() John Garry
2020-06-23 1:07 ` kernel test robot
2020-06-23 9:21 ` John Garry
2020-06-23 9:35 ` Rikard Falkeborn
2020-06-23 10:19 ` John Garry
2020-06-23 13:55 ` Rikard Falkeborn
2020-06-26 10:05 ` John Garry
2020-06-23 16:22 ` Robin Murphy
2020-06-24 8:15 ` John Garry
2020-07-16 10:20 ` Will Deacon
2020-07-16 10:26 ` John Garry
2020-07-08 13:00 ` [PATCH 0/4] iommu/arm-smmu-v3: Improve cmdq lock efficiency John Garry
2020-07-16 10:19 ` Will Deacon
2020-07-16 10:22 ` Will Deacon [this message]
2020-07-16 10:28 ` Will Deacon
2020-07-16 10:56 ` John Garry
2020-07-16 11:22 ` Robin Murphy
2020-07-16 11:30 ` John Garry
2020-07-16 11:32 ` Will Deacon
2020-07-16 16:50 ` John Garry
2020-07-16 13:31 ` John Garry
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