From: Will Deacon <will@kernel.org>
To: John Garry <john.garry@huawei.com>
Cc: trivial@kernel.org, maz@kernel.org, joro@8bytes.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 10:24 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1592846920-45338-1-git-send-email-john.garry@huawei.com>
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
[not found] ` <1592846920-45338-5-git-send-email-john.garry@huawei.com>
[not found] ` <202006230905.3HpPgtSC%lkp@intel.com>
[not found] ` <5ba2e240-b324-d316-c00c-38c03ee49baa@huawei.com>
2020-06-23 16:22 ` [PATCH 4/4] iommu/arm-smmu-v3: Remove cmpxchg() in arm_smmu_cmdq_issue_cmdlist() Robin Murphy
2020-06-24 8:15 ` John Garry
[not found] ` <CADRDgG4=uD3Ni6r7D3kHdSo=ketaXKGririHfFvPYq4qz8KjfQ@mail.gmail.com>
[not found] ` <ee2d7a1e-3e22-f25a-ced9-82ccced28f8c@huawei.com>
[not found] ` <CADRDgG5pOstGK=fm8s3Be_v8+vc-EyRYmpiMsTCeK-rMk2ZRQQ@mail.gmail.com>
2020-06-26 10:05 ` John Garry
2020-07-16 10:20 ` Will Deacon
2020-07-16 10:26 ` John Garry
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