From: David Miller <davem@davemloft.net>
To: mst@redhat.com
Cc: jasowang@redhat.com, eric.dumazet@gmail.com,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
ebiederm@xmission.com, Ian.Campbell@citrix.com
Subject: Re: [PATCHv3 0/6] tun zerocopy support
Date: Sun, 22 Jul 2012 12:40:20 -0700 (PDT) [thread overview]
Message-ID: <20120722.124020.1299343386554149788.davem@davemloft.net> (raw)
In-Reply-To: <20120721220534.GA22912@redhat.com>
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: Sun, 22 Jul 2012 01:05:34 +0300
> I agree a small win in CPU use is nothing to write home about,
> I don't yet understand why the win is so small - macvtap has zero copy
> supported for a while and it has exactly same issues.
> I hope adding tun zerocopy support upstream will help us
> make progress faster and find the bottleneck, so far not many people use
> macvtap so zero copy mode there didn't make progress.
>
> I do know why local performance regresses with zero copy enabled:
> instead of plain copy to user we got get user pages and then memcpy.
> We'll need some logic here to detect this and turn off zero copy.
>
> The core patches will also be helpful for Ian's more ambitious work.
>
> Overall I think it's a step in the right direction and it's easier to
> work if core parts are upstream, but if you think we need to wait
> until the gains are more significant, I understand that too.
Ok, I've applied this series, let's see what happens.
prev parent reply other threads:[~2012-07-22 19:40 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-20 19:23 [PATCHv3 0/6] tun zerocopy support Michael S. Tsirkin
2012-07-20 19:23 ` [PATCHv3 1/6] skbuff: add an api to orphan frags Michael S. Tsirkin
2012-07-20 19:23 ` [PATCHv3 2/6] skbuff: convert to skb_orphan_frags Michael S. Tsirkin
2012-07-20 19:23 ` [PATCHv3 4/6] tun: orphan frags on xmit Michael S. Tsirkin
2012-07-20 19:23 ` [PATCHv3 5/6] net: orphan frags on receive Michael S. Tsirkin
2012-07-20 19:23 ` [PATCHv3 3/6] skbuff: export skb_copy_ubufs Michael S. Tsirkin
2012-07-20 19:23 ` [PATCHv3 6/6] tun: experimental zero copy tx support Michael S. Tsirkin
2012-07-21 0:49 ` [PATCHv3 0/6] tun zerocopy support David Miller
2012-07-21 22:05 ` Michael S. Tsirkin
2012-07-22 19:40 ` David Miller [this message]
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