linux-kernel - Re: [PATCH RFC] [INET]: Get cirtical word in first 64bit of cache line

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Date:	Sun, 02 Dec 2012 09:20:11 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ling Ma <ling.ma.program@...il.com>
Cc:	linux-kernel@...r.kernel.org, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH RFC] [INET]: Get cirtical word in first 64bit of cache
 line

On Sun, 2012-12-02 at 21:25 +0800, Ling Ma wrote:
> Hi Eric,
> 
> Attached benchmark test-cwf.c(cc -o test-cwf test-cwf.c), the result
> shows when last level cache(LLC) miss and CPU fetches data from
> memory, critical word as first 64bit member in cache line has better
> performance(costs 158290336 cycles ) than other positions(offset 0x10,
> costs 164100732 ) in cache line, the performance is improved by 3.6%
> in this case.
> cpu-info is also involved too.
> 
> Thanks
> Ling

Thanks Ling.

Note that I was more interested by the case we read more fields per
cache line, like we do in tcp lookups. (skc_daddr, skc_rcv_saddr,
skc_bound_dev_if, skc_net).

I made changes to net-next to prepare your patch. 

You'll have to move both skc_rxhash & skc_portpair before the
skc_addrpair.

I have to fix an endianness sparse problem, I'll send a patch for this
in a separate thread right now.



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