From: Will Deacon <will.deacon@arm.com>
To: John Garry <john.garry@huawei.com>
Cc: Vijay Kilary <vkilari@codeaurora.org>,
Jean-Philippe Brucker <jean-philippe.brucker@arm.com>,
Jon Masters <jcm@redhat.com>, Jan Glauber <jglauber@marvell.com>,
iommu@lists.linux-foundation.org,
Jayachandran Chandrasekharan Nair <jnair@marvell.com>,
Robin Murphy <robin.murphy@arm.com>
Subject: Re: [RFC CFT 0/6] Try to reduce lock contention on the SMMUv3 command queue
Date: Mon, 17 Jun 2019 19:15:48 +0100 [thread overview]
Message-ID: <20190617181548.GO30800@fuggles.cambridge.arm.com> (raw)
In-Reply-To: <7c5a590c-dd7f-2e17-6c99-ac95ff59af07@huawei.com>
Hi John,
On Mon, Jun 17, 2019 at 02:38:59PM +0100, John Garry wrote:
> On 11/06/2019 14:45, Will Deacon wrote:
> > Hi all,
> >
> > This patch series is an attempt to reduce lock contention when inserting
> > commands into the Arm SMMUv3 command queue. Unfortunately, our initial
> > benchmarking has shown mixed results across the board and the changes in
> > the last patch don't appear to justify their complexity. Based on that,
> > I only plan to queue the first patch for the time being.
> >
> > Anyway, before I park this series, I thought it was probably worth
> > sharing it in case it's useful to somebody. If you have a system where
> > you believe I/O performance to be limited by the SMMUv3 command queue
> > then please try these patches and let me know what happens, even if it's
> > just more bad news.
> >
> > Patches based on 5.2-rc3. I've also pushed them out to my iommu/devel
> > branch for the moment:
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/log/?h=iommu/devel
> >
>
> For command queue lock contention, we had this series previously:
> https://lore.kernel.org/linux-iommu/61b4c3e5f1322dfe96ca2062a7fe058298340996.1539782799.git.robin.murphy@arm.com/#t
>
> I am just wondering does this have any future?
The functionality of that series is subsumed by the patches I've posted
here, although if I can't get the cmpxchg() loop working well here then
we could revisit just making the change proposed by Robin. The problem is
that we'll still have serialisation on access to the command queue, and
therefore it will remain a scalability bottleneck as long as the fast-path
needs to queue for a lock.
However, I've still got a few tricks up my sleeve so I'm hoping to get a
new version of this lot out in the coming weeks.
Will
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
prev parent reply other threads:[~2019-06-17 18:15 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-11 13:45 [RFC CFT 0/6] Try to reduce lock contention on the SMMUv3 command queue Will Deacon
2019-06-11 13:45 ` [RFC CFT 1/6] iommu/arm-smmu-v3: Increase maximum size of queues Will Deacon
2019-06-11 13:45 ` [RFC CFT 2/6] iommu/arm-smmu-v3: Separate s/w and h/w views of prod and cons indexes Will Deacon
2019-06-11 13:46 ` [RFC CFT 3/6] iommu/arm-smmu-v3: Drop unused 'q' argument from Q_OVF macro Will Deacon
2019-06-11 13:46 ` [RFC CFT 4/6] iommu/arm-smmu-v3: Move low-level queue fields out of arm_smmu_queue Will Deacon
2019-06-11 13:46 ` [RFC CFT 5/6] iommu/arm-smmu-v3: Operate directly on low-level queue where possible Will Deacon
2019-06-11 13:46 ` [RFC CFT 6/6] iommu/arm-smmu-v3: Reduce contention during command-queue insertion Will Deacon
2019-06-17 13:38 ` [RFC CFT 0/6] Try to reduce lock contention on the SMMUv3 command queue John Garry
2019-06-17 18:15 ` Will Deacon [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190617181548.GO30800@fuggles.cambridge.arm.com \
--to=will.deacon@arm.com \
--cc=iommu@lists.linux-foundation.org \
--cc=jcm@redhat.com \
--cc=jean-philippe.brucker@arm.com \
--cc=jglauber@marvell.com \
--cc=jnair@marvell.com \
--cc=john.garry@huawei.com \
--cc=robin.murphy@arm.com \
--cc=vkilari@codeaurora.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).