Date: Thu, 08 Apr 2010 00:05:57 -0700 (PDT)
Message-Id: <20100408.000557.180546976.davem@davemloft.net>
To: eric.dumazet@gmail.com
Cc: yanmin_zhang@linux.intel.com, cl@linux-foundation.org,
       penberg@cs.helsinki.fi, netdev@vger.kernel.org, tj@kernel.org,
       alex.shi@intel.com, linux-kernel@vger.kernel.org, ling.ma@intel.com,
       tim.c.chen@intel.com, akpm@linux-foundation.org
Subject: Re: hackbench regression due to commit 9dfc6e68bfe6e
From: David Miller <davem@davemloft.net>
In-Reply-To: <1270710019.2215.4.camel@edumazet-laptop>
References: <1270702774.8141.49.camel@edumazet-laptop>
	<1270705153.8141.58.camel@edumazet-laptop>
	<1270710019.2215.4.camel@edumazet-laptop>
Mime-Version: 1.0
Content-Type: Text/Plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 929
Lines: 24

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Thu, 08 Apr 2010 09:00:19 +0200

> If run individually, the tests results are more what we would expect
> (slow), but if machine runs the two set of process concurrently, each
> group runs much faster...

BTW, I just discovered (thanks to the function graph tracer, woo hoo!)
that loopback TCP packets get fully checksum validated on receive.

I'm trying to figure out why skb->ip_summed ends up being
CHECKSUM_NONE in tcp_v4_rcv() even though it gets set to
CHECKSUM_PARTIAL in tcp_sendmsg().

I wonder how much this accounts for some of the hackbench
oddities... and other regressions in loopback tests we've seen.
:-)

Just FYI...
--
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/