DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws;
  s=s1024; d=ms2.inr.ac.ru;
  b=Y2alxgB+/WmAcOVrNyMBzCaMtbuk61hZzP+q+U0LA9WWEgSuJ/CxY+zGfJa1GZpFbuG4h3BNUeRPFNEL9wqQiiINVCXVBOezFnoXTCuJ7/OLDojo+8+2kTFTIAn8cytahxtx3QOvIgJkyBLHsI++/cpUGc/M4L1rP+GtEc3pBdc=;
Date: Tue, 19 Sep 2006 01:03:21 +0400
From: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
To: Andi Kleen <ak@suse.de>
Cc: "Vladimir B. Savkin" <master@sectorb.msk.ru>,
       Jesper Dangaard Brouer <hawk@diku.dk>,
       Harry Edmon <harry@atmos.washington.edu>, linux-kernel@vger.kernel.org,
       netdev@vger.kernel.org
Subject: Re: Network performance degradation from 2.6.11.12 to 2.6.16.20
Message-ID: <20060918210321.GA4780@ms2.inr.ac.ru>
References: <4492D5D3.4000303@atmos.washington.edu> <200609181754.37623.ak@suse.de> <20060918162847.GA4863@ms2.inr.ac.ru> <200609181850.22851.ak@suse.de>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <200609181850.22851.ak@suse.de>
User-Agent: Mutt/1.5.6i
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1255
Lines: 39

Hello!

> But that never happens right? 

Right.

Well, not right. It happens. Simply because you get packet
with newer timestamp after previous handler saw this packet
and did some actions. I just do not see any bad consequences.


> And do you have some other prefered way to solve this? Even if the timer
> was fast it would be still good to avoid it in the fast path when DHCPD
> is running.

No. The way, which you suggested, seems to be the best.


1. It even does not disable possibility to record timestamp inside
   driver, which Alan was afraid of. The sequence is:

	if (!skb->tstamp.off_sec)
                net_timestamp(skb);

2. Maybe, netif_rx() should continue to get timestamp in netif_rx().

3. NAPI already introduced almost the same inaccuracy. And it is really
   silly to waste time getting timestamp in netif_receive_skb() a few
   moments before the packet is delivered to a socket.

4. ...but clock source, which takes one of top lines in profiles
   must be repaired yet. :-)

Alexey
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/