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From: "Michael S. Tsirkin" <mst@redhat.com>
To: Shirley Ma <mashirle@us.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>, Avi Kivity <avi@redhat.com>,
	"Xin, Xiaohui" <xiaohui.xin@intel.com>,
	David Miller <davem@davemloft.net>,
	netdev@vger.kernel.org, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 2/2] macvtap: TX zero copy between guest and host kernel
Date: Wed, 15 Sep 2010 12:10:00 +0200	[thread overview]
Message-ID: <20100915101000.GB28016@redhat.com> (raw)
In-Reply-To: <1284531675.24603.259.camel@localhost.localdomain>

On Tue, Sep 14, 2010 at 11:21:15PM -0700, Shirley Ma wrote:
> On Wed, 2010-09-15 at 07:12 +0200, Michael S. Tsirkin wrote:
> > Yes, I agree this patch is useful for demo purposes:
> > simple, and shows what kind of performance gains
> > we can expect for TX. 
> 
> Any other issue you can see in this patch beside vhost descriptors
> update?

Another issue is that macvtap can be bound to almost
anything, including e.g. a tap device or a bridge,
which might hang on to skb fragments for unlimited time.
Zero copy TX won't easily work there.
I can imagine either somehow triggering a data copy after the
fact (hard), or detecting such devices and avoiding
zero copy (unfortunate for guest to guest, and drivers
will need tuning).

>  Don't you think once I address vhost_add_used_and_signal update
> issue, it is a simple and complete patch for macvtap TX zero copy?
> 
> Thanks
> Shirley

I like the fact that the patch is simple. Unfortunately
I suspect it'll stop being simple by the time it's complete :)

-- 
MST

  reply	other threads:[~2010-09-15 10:16 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-09-13 20:43 [RFC PATCH 0/1] macvtap TX zero copy between guest and host kernel Shirley Ma
2010-09-13 20:47 ` RFC PATCH 1/2] macvtap: A new sock zero copy flag Shirley Ma
2010-09-13 20:48 ` [RFC PATCH 2/2] macvtap: TX zero copy between guest and host kernel Shirley Ma
2010-09-14  3:17   ` David Miller
2010-09-14  9:12     ` Avi Kivity
2010-09-14 15:05       ` Shirley Ma
2010-09-14 15:21         ` Arnd Bergmann
2010-09-14 15:22           ` Michael S. Tsirkin
2010-09-14 16:00             ` Shirley Ma
2010-09-14 16:29               ` Michael S. Tsirkin
2010-09-14 17:02                 ` Shirley Ma
2010-09-14 18:27                   ` Michael S. Tsirkin
2010-09-14 18:49                     ` Shirley Ma
2010-09-14 19:01                       ` Michael S. Tsirkin
2010-09-14 19:20                         ` Shirley Ma
2010-09-15  5:31                           ` Michael S. Tsirkin
2010-09-14 19:36                         ` Shirley Ma
2010-09-15  5:12                           ` Michael S. Tsirkin
2010-09-15  6:21                             ` Shirley Ma
2010-09-15 10:10                               ` Michael S. Tsirkin [this message]
2010-09-15 14:52                                 ` Shirley Ma
2010-09-15 15:04                                   ` Michael S. Tsirkin
2010-09-15 15:39                                     ` Michael S. Tsirkin
2010-09-15 17:00                                       ` Shirley Ma
2010-09-15 17:30                                         ` Michael S. Tsirkin
2010-09-15 18:48                                           ` Shirley Ma
2010-09-29  3:24                                   ` Shirley Ma
2010-09-29  8:16                                     ` Michael S. Tsirkin
2010-09-29  8:28                                       ` Michael S. Tsirkin
2010-09-29 14:33                                         ` Shirley Ma
2010-09-29 14:56                                         ` Shirley Ma
2010-09-29 14:31                                       ` Shirley Ma
2010-09-29 14:37                                       ` Shirley Ma
2010-09-29 15:14                                     ` Michael S. Tsirkin
2010-09-29 15:23                                       ` Shirley Ma
2010-09-15  2:46                 ` Xin, Xiaohui
2010-09-15  9:58                   ` Michael S. Tsirkin
2010-09-16  8:18                     ` Xin, Xiaohui
2010-09-16 10:02                       ` Michael S. Tsirkin
2010-09-15  1:56           ` Xin, Xiaohui
2010-09-15  1:50         ` Xin, Xiaohui
2010-09-15  2:40           ` Shirley Ma
2010-09-15  2:55             ` Xin, Xiaohui
2010-09-15  5:27             ` Michael S. Tsirkin
2010-09-15  6:17               ` Shirley Ma
2010-09-14 12:05 ` [RFC PATCH 0/1] macvtap " Michael S. Tsirkin
2010-09-14 15:15   ` Shirley Ma

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