From: Rusty Russell <rusty@rustcorp.com.au>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Ohad Ben-Cohen <ohad@wizery.com>
Cc: linux-arm-kernel@lists.infradead.org,
"Michael S. Tsirkin" <mst@redhat.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
virtualization@lists.linux-foundation.org
Subject: Re: [RFC] virtio: use mandatory barriers for remote processor vdevs
Date: Sat, 03 Dec 2011 15:44:36 +1030 [thread overview]
Message-ID: <87hb1iqls3.fsf@rustcorp.com.au> (raw)
In-Reply-To: <1322867384.11728.20.camel@pasglop>
On Sat, 03 Dec 2011 10:09:44 +1100, Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> On Tue, 2011-11-29 at 14:31 +0200, Ohad Ben-Cohen wrote:
> > A trivial, albeit sub-optimal, solution would be to simply revert
> > commit d57ed95 "virtio: use smp_XX barriers on SMP". Obviously, though,
> > that's going to have a negative impact on performance of SMP-based
> > virtualization use cases.
>
> Have you measured the impact of using normal barriers (non-SMP ones)
> like we use on normal HW drivers unconditionally ?
>
> IE. If the difference is small enough I'd say just go for it and avoid
> the bloat.
Yep. Plan is:
1) Measure the difference.
2) Difference unmeassurable? Use normal barriers (ie. revert d57ed95).
3) Difference small? Revert d57ed95 for 3.2, revisit for 3.3.
4) Difference large? Runtime switch based on "if you're PCI" for 3.2,
revisit for 3.3.
Cheers,
Rusty.
next prev parent reply other threads:[~2011-12-03 5:14 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1322569886-13055-1-git-send-email-ohad@wizery.com>
2011-11-29 13:11 ` [RFC] virtio: use mandatory barriers for remote processor vdevs Michael S. Tsirkin
2011-11-29 13:57 ` Ohad Ben-Cohen
2011-11-29 15:16 ` Michael S. Tsirkin
2011-11-30 11:45 ` Ohad Ben-Cohen
2011-11-30 14:59 ` Michael S. Tsirkin
2011-11-30 16:04 ` Ohad Ben-Cohen
[not found] ` <CAK=WgbYyFdLftE_kp2_JOThVhn-FzGsDqVqKn0Jwm2teQyZBNA@mail.gmail.com>
2011-11-30 16:15 ` Michael S. Tsirkin
2011-11-30 16:24 ` Ohad Ben-Cohen
2011-11-30 23:27 ` Ohad Ben-Cohen
2011-11-30 23:43 ` Michael S. Tsirkin
2011-12-01 6:20 ` Ohad Ben-Cohen
2011-11-29 15:19 ` Michael S. Tsirkin
2011-11-30 11:55 ` Ohad Ben-Cohen
2011-11-30 14:50 ` Michael S. Tsirkin
2011-11-30 22:43 ` Ohad Ben-Cohen
2011-11-30 23:13 ` Michael S. Tsirkin
2011-12-01 2:28 ` Rusty Russell
2011-12-01 7:15 ` Ohad Ben-Cohen
2011-12-01 8:12 ` Michael S. Tsirkin
2011-12-02 0:26 ` Rusty Russell
2011-12-01 6:14 ` Ohad Ben-Cohen
2011-12-01 9:09 ` Michael S. Tsirkin
2011-12-02 23:09 ` Benjamin Herrenschmidt
2011-12-03 5:14 ` Rusty Russell [this message]
2011-12-11 12:25 ` Michael S. Tsirkin
2011-12-11 22:27 ` Benjamin Herrenschmidt
2011-12-12 3:06 ` Amos Kong
2011-12-12 5:12 ` Rusty Russell
2011-12-12 23:56 ` Amos Kong
2011-12-19 2:35 ` Rusty Russell
2011-12-19 2:19 ` Amos Kong
2011-12-19 2:41 ` Benjamin Herrenschmidt
2011-12-19 7:21 ` Amos Kong
2011-12-19 2:50 ` Amos Kong
2011-12-19 8:37 ` Rusty Russell
2011-12-03 6:01 ` Ohad Ben-Cohen
2011-11-29 12:31 Ohad Ben-Cohen
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