From: Stefan Hajnoczi <stefanha@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>,
linux-scsi <linux-scsi@vger.kernel.org>,
kvm <kvm@vger.kernel.org>, "Michael S. Tsirkin" <mst@redhat.com>,
hutao@cn.fujitsu.com, linux-kernel <linux-kernel@vger.kernel.org>,
Linux Virtualization <virtualization@lists.linux-foundation.org>
Subject: Re: [PATCH v2 1/5] virtio: add functions for piecewise addition of buffers
Date: Wed, 19 Dec 2012 13:40:57 +0100 [thread overview]
Message-ID: <CAJSP0QUNQHSak_jUWA0jfDuKgfVFsyJb0252OxWzQzUcj653bg@mail.gmail.com> (raw)
In-Reply-To: <50D1AD38.7070606@redhat.com>
On Wed, Dec 19, 2012 at 1:04 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
> Il 19/12/2012 11:47, Stefan Hajnoczi ha scritto:
>> On Tue, Dec 18, 2012 at 01:32:48PM +0100, Paolo Bonzini wrote:
>> What is the purpose of count_sg?
>
> It is needed to decide whether to use an indirect or a direct buffer.
> The idea is to avoid a memory allocation if the driver is providing us
> with separate sg elements (under the assumption that they will be few).
Ah, this makes sense now. I saw it affects the decision whether to go
indirect or not but it wasn't obvious why.
> Originally I wanted to use a mix of direct and indirect buffer (direct
> if add_buf received a one-element scatterlist, otherwise indirect). It
> would have had the same effect, without having to specify count_sg in
> advance. The spec is not clear if that is allowed or not, but in the
> end they do not work with either QEMU or vhost, so I chose this
> alternative instead.
Okay.
Stefan
WARNING: multiple messages have this Message-ID (diff)
From: Stefan Hajnoczi <stefanha@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm <kvm@vger.kernel.org>,
linux-scsi <linux-scsi@vger.kernel.org>,
"Michael S. Tsirkin" <mst@redhat.com>,
hutao@cn.fujitsu.com, linux-kernel <linux-kernel@vger.kernel.org>,
Linux Virtualization <virtualization@lists.linux-foundation.org>,
Stefan Hajnoczi <stefanha@redhat.com>
Subject: Re: [PATCH v2 1/5] virtio: add functions for piecewise addition of buffers
Date: Wed, 19 Dec 2012 13:40:57 +0100 [thread overview]
Message-ID: <CAJSP0QUNQHSak_jUWA0jfDuKgfVFsyJb0252OxWzQzUcj653bg@mail.gmail.com> (raw)
In-Reply-To: <50D1AD38.7070606@redhat.com>
On Wed, Dec 19, 2012 at 1:04 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
> Il 19/12/2012 11:47, Stefan Hajnoczi ha scritto:
>> On Tue, Dec 18, 2012 at 01:32:48PM +0100, Paolo Bonzini wrote:
>> What is the purpose of count_sg?
>
> It is needed to decide whether to use an indirect or a direct buffer.
> The idea is to avoid a memory allocation if the driver is providing us
> with separate sg elements (under the assumption that they will be few).
Ah, this makes sense now. I saw it affects the decision whether to go
indirect or not but it wasn't obvious why.
> Originally I wanted to use a mix of direct and indirect buffer (direct
> if add_buf received a one-element scatterlist, otherwise indirect). It
> would have had the same effect, without having to specify count_sg in
> advance. The spec is not clear if that is allowed or not, but in the
> end they do not work with either QEMU or vhost, so I chose this
> alternative instead.
Okay.
Stefan
next prev parent reply other threads:[~2012-12-19 12:48 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-18 12:32 [PATCH v2 0/5] Multiqueue virtio-scsi, and API for piecewise buffer submission Paolo Bonzini
2012-12-18 12:32 ` Paolo Bonzini
2012-12-18 12:32 ` [PATCH v2 1/5] virtio: add functions for piecewise addition of buffers Paolo Bonzini
2012-12-18 12:32 ` Paolo Bonzini
2012-12-18 13:36 ` Michael S. Tsirkin
2012-12-18 13:36 ` Michael S. Tsirkin
2012-12-18 13:43 ` Paolo Bonzini
2012-12-18 13:43 ` Paolo Bonzini
2012-12-18 13:59 ` Michael S. Tsirkin
2012-12-18 13:59 ` Michael S. Tsirkin
2012-12-18 14:32 ` Paolo Bonzini
2012-12-18 14:32 ` Paolo Bonzini
2012-12-18 15:06 ` Michael S. Tsirkin
2012-12-18 15:06 ` Michael S. Tsirkin
2012-12-19 10:47 ` Stefan Hajnoczi
2012-12-19 10:47 ` Stefan Hajnoczi
2012-12-19 12:04 ` Paolo Bonzini
2012-12-19 12:04 ` Paolo Bonzini
2012-12-19 12:40 ` Stefan Hajnoczi [this message]
2012-12-19 12:40 ` Stefan Hajnoczi
2012-12-19 16:51 ` Michael S. Tsirkin
2012-12-19 16:51 ` Michael S. Tsirkin
2012-12-19 16:52 ` Michael S. Tsirkin
2012-12-19 16:52 ` Michael S. Tsirkin
2013-01-02 5:03 ` Rusty Russell
2013-01-02 5:03 ` Rusty Russell
2013-01-03 8:58 ` Wanlong Gao
2013-01-03 8:58 ` Wanlong Gao
2013-01-03 8:58 ` Wanlong Gao
2013-01-06 23:32 ` Rusty Russell
2013-01-06 23:32 ` Rusty Russell
2013-01-06 23:32 ` Rusty Russell
2013-01-03 9:22 ` Paolo Bonzini
2013-01-03 9:22 ` Paolo Bonzini
2013-01-07 0:02 ` Rusty Russell
2013-01-07 0:02 ` Rusty Russell
2013-01-07 14:27 ` Paolo Bonzini
2013-01-08 0:12 ` Rusty Russell
2013-01-08 0:12 ` Rusty Russell
2013-01-10 8:44 ` Paolo Bonzini
2012-12-18 12:32 ` [PATCH v2 2/5] virtio-scsi: use functions for piecewise composition " Paolo Bonzini
2012-12-18 12:32 ` Paolo Bonzini
2012-12-18 13:37 ` Michael S. Tsirkin
2012-12-18 13:37 ` Michael S. Tsirkin
2012-12-18 13:35 ` Paolo Bonzini
2012-12-18 13:35 ` Paolo Bonzini
2012-12-18 12:32 ` [PATCH v2 3/5] virtio-scsi: redo allocation of target data Paolo Bonzini
2012-12-18 12:32 ` Paolo Bonzini
2012-12-18 12:32 ` [PATCH v2 4/5] virtio-scsi: pass struct virtio_scsi to virtqueue completion function Paolo Bonzini
2012-12-18 12:32 ` Paolo Bonzini
2012-12-18 12:32 ` [PATCH v2 5/5] virtio-scsi: introduce multiqueue support Paolo Bonzini
2012-12-18 13:57 ` Michael S. Tsirkin
2012-12-18 13:57 ` Michael S. Tsirkin
2012-12-18 14:08 ` Paolo Bonzini
2012-12-18 14:08 ` Paolo Bonzini
2012-12-18 15:03 ` Michael S. Tsirkin
2012-12-18 15:03 ` Michael S. Tsirkin
2012-12-18 15:51 ` Paolo Bonzini
2012-12-18 15:51 ` Paolo Bonzini
2012-12-18 16:02 ` Michael S. Tsirkin
2012-12-18 16:02 ` Michael S. Tsirkin
2012-12-25 12:41 ` Wanlong Gao
2012-12-25 12:41 ` Wanlong Gao
2012-12-19 11:27 ` Stefan Hajnoczi
2012-12-19 11:27 ` Stefan Hajnoczi
2012-12-18 12:32 ` Paolo Bonzini
2012-12-18 13:42 ` [PATCH v2 0/5] Multiqueue virtio-scsi, and API for piecewise buffer submission Michael S. Tsirkin
2012-12-18 13:42 ` Michael S. Tsirkin
2012-12-24 6:44 ` Wanlong Gao
2012-12-24 6:44 ` Wanlong Gao
2012-12-18 22:18 ` Rolf Eike Beer
2012-12-19 8:52 ` Paolo Bonzini
2012-12-19 8:52 ` Paolo Bonzini
2012-12-19 11:32 ` Michael S. Tsirkin
2012-12-19 11:32 ` Michael S. Tsirkin
2012-12-18 22:18 ` Rolf Eike Beer
2013-01-15 9:48 ` [PATCH 1/2] virtio-scsi: split out request queue set affinity function Wanlong Gao
2013-01-15 9:48 ` Wanlong Gao
2013-01-15 9:50 ` [PATCH 2/2] virtio-scsi: reset virtqueue affinity when doing cpu hotplug Wanlong Gao
2013-01-15 9:50 ` Wanlong Gao
2013-01-16 3:31 ` Rusty Russell
2013-01-16 3:31 ` Rusty Russell
2013-01-16 3:55 ` Wanlong Gao
2013-01-16 3:55 ` Wanlong Gao
2013-02-06 17:27 ` Paolo Bonzini
2013-02-06 17:27 ` Paolo Bonzini
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