From: Andi Kleen <andi@firstfloor.org>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Andi Kleen <andi@firstfloor.org>,
Octavian Purdila <opurdila@ixiacom.com>,
Lucian Adrian Grijincu <lgrijincu@ixiacom.com>,
netdev@vger.kernel.org
Subject: Re: [RFC] [PATCH] udp: optimize lookup of UDP sockets to by including destination address in the hash key
Date: Thu, 5 Nov 2009 15:54:28 +0100 [thread overview]
Message-ID: <20091105145428.GS31511@one.firstfloor.org> (raw)
In-Reply-To: <4AF2CCD9.7010507@gmail.com>
> I assume cache is cold or even on other cpu (worst case), dealing with
> 100.000+ sockets or so...
Other CPU cache hit is actually typically significantly
faster than a DRAM access (unless you're talking about a very large NUMA
system and a remote CPU far away)
>
> If workload fits in one CPU cache/registers, we dont mind taking one
> or two cache lines per object, obviously.
It's more like part of your workload needs to fit.
For example if you use a tree and the higher levels fit into
the cache, having a few levels in the tree is (approximately) free.
That's why I'm not always fond of large hash tables. They pretty
much guarantee a lot of cache misses under high load, because
they have little locality.
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
next prev parent reply other threads:[~2009-11-05 14:54 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-04 21:03 [RFC] [PATCH] udp: optimize lookup of UDP sockets to by including destination address in the hash key Lucian Adrian Grijincu
2009-11-04 21:30 ` Eric Dumazet
2009-11-04 23:04 ` Octavian Purdila
2009-11-04 23:32 ` Eric Dumazet
2009-11-05 12:12 ` Andi Kleen
2009-11-05 13:02 ` Eric Dumazet
2009-11-05 14:54 ` Andi Kleen [this message]
2009-11-05 15:07 ` Eric Dumazet
2009-11-05 15:16 ` Andi Kleen
2009-11-05 16:25 ` Octavian Purdila
2009-11-05 16:36 ` Eric Dumazet
2009-11-05 17:03 ` Octavian Purdila
2009-11-05 17:39 ` Eric Dumazet
2009-11-06 18:34 ` Eric Dumazet
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