From: David Miller <davem@davemloft.net>
To: andi@firstfloor.org
Cc: therbert@google.com, netdev@vger.kernel.org
Subject: Re: [PATCH] Software receive packet steering
Date: Mon, 20 Apr 2009 03:46:28 -0700 (PDT) [thread overview]
Message-ID: <20090420.034628.224469114.davem@davemloft.net> (raw)
In-Reply-To: <87eivnpqde.fsf@basil.nowhere.org>
From: Andi Kleen <andi@firstfloor.org>
Date: Mon, 20 Apr 2009 12:32:29 +0200
> Tom Herbert <therbert@google.com> writes:
>
>> +got_hash:
>> + hash %= cpus_weight_nr(mask);
>
> That looks rather heavyweight even on modern CPUs. I bet it's 40-50+ cycles
> alone forth the hweight and the division. Surely that can be done better?
The standard way to do this is to compute a 32-bit jenkins
hash, and do a 64-bit multiply of this value with a suitable
reciprocol.
This is what skb_tx_hash() is doing in net/core/dev.c
next prev parent reply other threads:[~2009-04-20 10:46 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-08 22:48 [PATCH] Software receive packet steering Tom Herbert
2009-04-08 23:08 ` Stephen Hemminger
2009-04-08 23:09 ` Stephen Hemminger
2009-04-08 23:15 ` David Miller
2009-04-09 16:43 ` Tom Herbert
2009-04-09 18:23 ` Ben Hutchings
2009-04-09 21:17 ` David Miller
2009-04-09 0:36 ` David Miller
2009-04-09 4:40 ` Tom Herbert
2009-04-09 5:24 ` David Miller
2009-04-20 10:32 ` Andi Kleen
2009-04-20 10:46 ` David Miller [this message]
2009-04-21 3:26 ` Tom Herbert
2009-04-21 9:48 ` Eric Dumazet
2009-04-21 15:46 ` Stephen Hemminger
2009-04-21 18:52 ` Tom Herbert
2009-04-22 9:21 ` David Miller
2009-04-22 15:46 ` Tom Herbert
2009-04-22 18:49 ` Rick Jones
2009-04-22 20:44 ` Jesper Dangaard Brouer
2009-04-23 6:58 ` Jens Axboe
2009-04-23 7:25 ` David Miller
2009-04-23 7:29 ` Jens Axboe
2009-04-23 9:12 ` Jens Laas
2009-04-22 14:33 ` Martin Josefsson
2009-04-23 7:34 ` David Miller
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