linux-kernel - Re: [PATCH] x86: Run checksumming in parallel accross multiple alu's

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Message-ID: <1381848748.2045.50.camel@edumazet-glaptop.roam.corp.google.com>
Date:	Tue, 15 Oct 2013 07:52:28 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Sébastien Dugué <sebastien.dugue@...l.net>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Neil Horman <nhorman@...driver.com>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Subject: Re: [PATCH] x86: Run checksumming in parallel accross multiple alu's

On Tue, 2013-10-15 at 07:26 -0700, Eric Dumazet wrote:

> And the receiver should also do the same : (ethtool -K eth0 rx off)
> 
>     10.55%    netserver  [kernel.kallsyms]  [k]
> csum_partial_copy_generic            

I get the csum_partial() if disabling prequeue.

echo 1 >/proc/sys/net/ipv4/tcp_low_latency

    24.49%      swapper  [kernel.kallsyms]  [k]
csum_partial                        
                |
                --- csum_partial
                    skb_checksum
                    __skb_checksum_complete_head
                    __skb_checksum_complete
                    tcp_rcv_established
                    tcp_v4_do_rcv
                    tcp_v4_rcv
                    ip_local_deliver_finish
                    ip_local_deliver
                    ip_rcv_finish
                    ip_rcv

So yes, we can call csum_partial() in receive path in this case.



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