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From: David Miller <davem@davemloft.net>
To: david.vrabel@citrix.com
Cc: netdev@vger.kernel.org, xen-devel@lists.xenproject.org,
	ian.campbell@citrix.com, wei.liu2@citrix.com,
	malcolm.crossley@citrix.com
Subject: Re: [PATCHv1 net-next] xen-netback: remove unconditional pull_skb_tail in guest Tx path
Date: Tue, 04 Nov 2014 16:41:13 -0500 (EST)	[thread overview]
Message-ID: <20141104.164113.2265592775058059992.davem@davemloft.net> (raw)
In-Reply-To: <1415035431-27485-1-git-send-email-david.vrabel@citrix.com>

From: David Vrabel <david.vrabel@citrix.com>
Date: Mon, 3 Nov 2014 17:23:51 +0000

> From: Malcolm Crossley <malcolm.crossley@citrix.com>
> 
> Unconditionally pulling 128 bytes into the linear buffer is not
> required. Netback has already grant copied up-to 128 bytes from the
> first slot of a packet into the linear buffer. The first slot normally
> contain all the IPv4/IPv6 and TCP/UDP headers.
> 
> The unconditional pull would often copy frag data unnecessarily.  This
> is a performance problem when running on a version of Xen where grant
> unmap avoids TLB flushes for pages which are not accessed.  TLB
> flushes can now be avoided for > 99% of unmaps (it was 0% before).
> 
> Grant unmap TLB flush avoidance will be available in a future version
> of Xen (probably 4.6).
> 
> Signed-off-by: Malcolm Crossley <malcolm.crossley@citrix.com>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>

Now that this has been discussed a bit, it is possible to get an ack or two?

Thanks.

  parent reply	other threads:[~2014-11-04 21:41 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-11-03 17:23 [PATCHv1 net-next] xen-netback: remove unconditional pull_skb_tail in guest Tx path David Vrabel
2014-11-03 17:39 ` Ian Campbell
2014-11-03 17:46   ` David Vrabel
2014-11-03 17:55     ` Ian Campbell
2014-11-03 18:23     ` [Xen-devel] " Zoltan Kiss
2014-11-04 21:17       ` David Miller
2014-11-04 21:43         ` Eric Dumazet
2014-11-05 10:46           ` David Vrabel
2014-11-05 10:53             ` Ian Campbell
2014-11-05  9:51         ` Ian Campbell
2014-11-05 17:15           ` David Miller
2014-11-04 21:41 ` David Miller [this message]
2014-11-05  9:53   ` Ian Campbell
2014-11-05 17:16     ` David Miller

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