From: Avi Kivity <avi@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: markmc@redhat.com, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
Sasha Levin <levinsasha928@gmail.com>
Subject: Re: [PATCH] virtio-ring: Use threshold for switching to indirect descriptors
Date: Sun, 04 Dec 2011 14:06:34 +0200 [thread overview]
Message-ID: <4EDB624A.3030403@redhat.com> (raw)
In-Reply-To: <20111204120132.GB18758@redhat.com>
On 12/04/2011 02:01 PM, Michael S. Tsirkin wrote:
> >
> > How much better?
> >
> > I think that if indirects benefit networking, then we're doing something
> > wrong. What's going on? Does the ring get filled too early? If so we
> > should expand it.
>
> The ring is physically contigious.
> With 256 entries and 64 bytes each, that's already 16K.
A descriptor is just 16 bytes. There's also the used ring, but that's a
mistake if you have out of order completion. We should have used copying.
16kB worth of descriptors is 1024 entries. With 4kB buffers, that's 4MB
worth of data, or 4 ms at 10GbE line speed. With 1500 byte buffers it's
just 1.5 ms. In any case I think it's sufficient.
--
error compiling committee.c: too many arguments to function
WARNING: multiple messages have this Message-ID (diff)
From: Avi Kivity <avi@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Sasha Levin <levinsasha928@gmail.com>,
Rusty Russell <rusty@rustcorp.com.au>,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
markmc@redhat.com
Subject: Re: [PATCH] virtio-ring: Use threshold for switching to indirect descriptors
Date: Sun, 04 Dec 2011 14:06:34 +0200 [thread overview]
Message-ID: <4EDB624A.3030403@redhat.com> (raw)
In-Reply-To: <20111204120132.GB18758@redhat.com>
On 12/04/2011 02:01 PM, Michael S. Tsirkin wrote:
> >
> > How much better?
> >
> > I think that if indirects benefit networking, then we're doing something
> > wrong. What's going on? Does the ring get filled too early? If so we
> > should expand it.
>
> The ring is physically contigious.
> With 256 entries and 64 bytes each, that's already 16K.
A descriptor is just 16 bytes. There's also the used ring, but that's a
mistake if you have out of order completion. We should have used copying.
16kB worth of descriptors is 1024 entries. With 4kB buffers, that's 4MB
worth of data, or 4 ms at 10GbE line speed. With 1500 byte buffers it's
just 1.5 ms. In any case I think it's sufficient.
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2011-12-04 12:06 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-29 9:33 [PATCH] virtio-ring: Use threshold for switching to indirect descriptors Sasha Levin
2011-11-29 9:33 ` Sasha Levin
2011-11-29 12:56 ` Michael S. Tsirkin
2011-11-29 12:56 ` Michael S. Tsirkin
2011-11-29 13:34 ` Sasha Levin
2011-11-29 13:34 ` Sasha Levin
2011-11-29 13:54 ` Michael S. Tsirkin
2011-11-29 14:21 ` Sasha Levin
2011-11-29 14:21 ` Sasha Levin
2011-11-29 14:54 ` Michael S. Tsirkin
2011-11-29 14:54 ` Michael S. Tsirkin
2011-11-29 14:58 ` Avi Kivity
2011-11-29 14:58 ` Avi Kivity
2011-11-30 16:11 ` Sasha Levin
2011-11-30 16:11 ` Sasha Levin
2011-11-30 16:17 ` Sasha Levin
2011-11-30 16:17 ` Sasha Levin
2011-12-01 2:42 ` Rusty Russell
2011-12-01 2:42 ` Rusty Russell
2011-12-01 7:58 ` Michael S. Tsirkin
2011-12-01 7:58 ` Michael S. Tsirkin
2011-12-01 8:09 ` Sasha Levin
2011-12-01 8:09 ` Sasha Levin
2011-12-01 10:26 ` Michael S. Tsirkin
2011-12-01 10:26 ` Michael S. Tsirkin
2011-12-02 0:46 ` Rusty Russell
2011-12-02 0:46 ` Rusty Russell
2011-12-03 11:50 ` Sasha Levin
2011-12-03 11:50 ` Sasha Levin
2011-12-04 11:06 ` Michael S. Tsirkin
2011-12-04 11:06 ` Michael S. Tsirkin
2011-12-04 15:15 ` Michael S. Tsirkin
2011-12-04 15:15 ` Michael S. Tsirkin
2011-12-04 11:52 ` Avi Kivity
2011-12-04 11:52 ` Avi Kivity
2011-12-04 12:01 ` Michael S. Tsirkin
2011-12-04 12:01 ` Michael S. Tsirkin
2011-12-04 12:06 ` Avi Kivity [this message]
2011-12-04 12:06 ` Avi Kivity
2011-12-04 15:11 ` Michael S. Tsirkin
2011-12-04 15:11 ` Michael S. Tsirkin
2011-12-04 15:16 ` Avi Kivity
2011-12-04 15:16 ` Avi Kivity
2011-12-04 16:00 ` Michael S. Tsirkin
2011-12-04 16:00 ` Michael S. Tsirkin
2011-12-04 16:33 ` Avi Kivity
2011-12-04 16:33 ` Avi Kivity
2011-12-05 0:10 ` Rusty Russell
2011-12-05 0:10 ` Rusty Russell
2011-12-05 9:52 ` Avi Kivity
2011-12-05 9:52 ` Avi Kivity
2011-12-06 5:07 ` Rusty Russell
2011-12-06 5:07 ` Rusty Russell
2011-12-06 9:58 ` Avi Kivity
2011-12-06 9:58 ` Avi Kivity
2011-12-06 12:03 ` Rusty Russell
2011-12-06 12:03 ` Rusty Russell
2011-12-07 13:37 ` Avi Kivity
2011-12-07 13:37 ` Avi Kivity
2011-12-04 12:13 ` Sasha Levin
2011-12-04 12:13 ` Sasha Levin
2011-12-04 16:22 ` Michael S. Tsirkin
2011-12-04 16:22 ` Michael S. Tsirkin
2011-12-04 17:34 ` Sasha Levin
2011-12-04 17:34 ` Sasha Levin
2011-12-04 17:37 ` Avi Kivity
2011-12-04 17:37 ` Avi Kivity
2011-12-04 17:39 ` Sasha Levin
2011-12-04 17:39 ` Sasha Levin
2011-12-04 18:23 ` Sasha Levin
2011-12-04 18:23 ` Sasha Levin
2011-12-07 14:02 ` Sasha Levin
2011-12-07 14:02 ` Sasha Levin
2011-12-07 15:48 ` Michael S. Tsirkin
2011-12-07 15:48 ` Michael S. Tsirkin
2011-12-08 9:44 ` Rusty Russell
2011-12-08 9:44 ` Rusty Russell
2011-12-08 10:37 ` Sasha Levin
2011-12-08 10:37 ` Sasha Levin
2011-12-09 5:33 ` Rusty Russell
2011-12-09 5:33 ` Rusty Russell
2011-11-29 13:54 ` Michael S. Tsirkin
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