From: Will Deacon <will@kernel.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Russell King - ARM Linux admin <linux@armlinux.org.uk>,
linux-arm-kernel@lists.infradead.org
Subject: Re: SMMU performance
Date: Wed, 2 Oct 2019 10:02:34 +0100 [thread overview]
Message-ID: <20191002090233.rqpmhyax2qztyhsr@willie-the-truck> (raw)
In-Reply-To: <250d78f8-a4d1-5ff0-e537-e7c2a49c0bf4@arm.com>
On Mon, Sep 30, 2019 at 01:00:00PM +0100, Robin Murphy wrote:
> On 30/09/2019 12:54, Will Deacon wrote:
> > On Mon, Sep 30, 2019 at 12:45:28PM +0100, Robin Murphy wrote:
> > > The major changes in 5.4 are for SMMUv3, so won't impact your platform.
> >
> > I was wondering whether rigging up the gather stuff would help here but,
> > looking at the backtrace, the time is spent on the sync itself so I suspect
> > it won't help. Hmm... I wonder if we can do better using a sequence number
> > so that we can ride off the back of somebody else's sync?
>
> The trouble with v2 is that then we'd have to introduce locking around the
> invalidates as well, in order to keep track of what the last 'command'
> issued in each context was - that's almost certainly going to have far more
> overhead than eliding syncs could possibly save.
I was thinking along the lines of allocating an ID to each flush, and then
updating a sync ID on sync, so you can elide the sync if the sync ID is
greater than your flush ID. But it's vague and I didn't try to implement
anything.
Will
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next prev parent reply other threads:[~2019-10-02 9:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-30 11:00 SMMU performance Russell King - ARM Linux admin
2019-09-30 11:45 ` Robin Murphy
2019-09-30 11:54 ` Will Deacon
2019-09-30 12:00 ` Robin Murphy
2019-10-02 9:02 ` Will Deacon [this message]
2019-10-02 11:09 ` Robin Murphy
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