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From: Eric Dumazet <dada1@cosmosbay.com>
To: Alexey Dobriyan <adobriyan@gmail.com>
Cc: David Miller <davem@davemloft.net>,
	netdev@vger.kernel.org, shemminger@vyatta.com, "Zhang,
	Yanmin" <yanmin_zhang@linux.intel.com>
Subject: Re: [PATCH] net: make sure struct dst_entry refcount is aligned on 64 bytes
Date: Fri, 14 Nov 2008 14:37:38 +0100	[thread overview]
Message-ID: <491D7F22.9020707@cosmosbay.com> (raw)
In-Reply-To: <20081114132230.GA27462@x200.localdomain>

Alexey Dobriyan a écrit :

> Hmm, indeed.
> 
> I tried moving __refcnt et al to the very beginning, but it seems to make
> things worse (on x86_64, almost within statistical error).
> 
> And there is no way to use offset_of() inside struct definition. :-(

Yes, it is important that the beginning of structure contain read mostly fields.

refcnt being the most written field (incremented / decremented for each packet),
it is really important to move it outside of the first 128 bytes 
(192 bytes on 64 bit arches) of dst_entry

I wonder if some real hot dst_entries could be splitted (one copy for each stream),
to reduce ping-pongs.


  reply	other threads:[~2008-11-14 13:37 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-11-14  8:09 [PATCH] net: speedup dst_release() Eric Dumazet
2008-11-14  8:54 ` David Miller
2008-11-14  9:04   ` Eric Dumazet
2008-11-14  9:36     ` Alexey Dobriyan
2008-11-14 10:47       ` [PATCH] net: make sure struct dst_entry refcount is aligned on 64 bytes Eric Dumazet
2008-11-14 11:35         ` Alexey Dobriyan
2008-11-14 11:43           ` Eric Dumazet
2008-11-14 13:22             ` Alexey Dobriyan
2008-11-14 13:37               ` Eric Dumazet [this message]
2008-11-17  3:46         ` David Miller

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