netdev - Re: [PATCH v6] net: batch skb dequeueing from softnet input_pkt

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Date:	Sun, 02 May 2010 08:56:06 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	David Miller <davem@...emloft.net>, hadi@...erus.ca,
	xiaosuo@...il.com, therbert@...gle.com, shemminger@...tta.com,
	netdev@...r.kernel.org, lenb@...nel.org, arjan@...radead.org
Subject: Re: [PATCH v6] net: batch skb dequeueing from softnet
 input_pkt_queue

Le samedi 01 mai 2010 à 13:00 +0200, Andi Kleen a écrit :
> On Fri, Apr 30, 2010 at 04:38:57PM -0700, David Miller wrote:
> > From: Andi Kleen <ak@...goyle.fritz.box>
> > Date: Thu, 29 Apr 2010 23:41:44 +0200
> > 
> > >     Use io_schedule() in network stack to tell cpuidle governour to guarantee lower latencies
> > > 
> > >     XXX: probably too aggressive, some of these sleeps are not under high load.
> > > 
> > >     Based on a bug report from Eric Dumazet.
> > >     
> > >     Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> > 
> > I like this, except that we probably don't want the delayacct_blkio_*() calls
> > these things do.
> 
> Yes.
> 
> It needs more work, please don't apply it yet, to handle the "long sleep" case.
> 
> Still curious if it fixes Eric's test case.
> 

I tried it on the right spot (since my bench was only doing recvmsg()
calls, I had to patch wait_for_packet() in net/core/datagram.c

udp_recvmsg -> __skb_recv_datagram -> wait_for_packet ->
schedule_timeout

Unfortunatly, using io_schedule_timeout() did not solve the problem.

Tell me if you need some traces or something.

Thanks !

diff --git a/net/core/datagram.c b/net/core/datagram.c
index 95b851f..051fd5b 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -113,7 +113,7 @@ static int wait_for_packet(struct sock *sk, int *err, long *timeo_p)
 		goto interrupted;
 
 	error = 0;
-	*timeo_p = schedule_timeout(*timeo_p);
+	*timeo_p = io_schedule_timeout(*timeo_p);
 out:
 	finish_wait(sk_sleep(sk), &wait);
 	return error;


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