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Date: Fri, 01 May 2009 09:08:15 -0700 (PDT) From: David Miller <davem@...emloft.net> To: dada1@...mosbay.com Cc: andrew@...dna.net, jelaas@...il.com, netdev@...r.kernel.org Subject: Re: tx queue hashing hot-spots and poor performance (multiq, ixgbe) From: Eric Dumazet <dada1@...mosbay.com> Date: Fri, 01 May 2009 08:14:03 +0200 > [PATCH] net: skb_tx_hash() improvements > > When skb_rx_queue_recorded() is true, we dont want to use jash distribution > as the device driver exactly told us which queue was selected at RX time. > jhash makes a statistical shuffle, but this wont work with 8 static inputs. > > Later improvements would be to compute reciprocal value of real_num_tx_queues > to avoid a divide here. But this computation should be done once, > when real_num_tx_queues is set. This needs a separate patch, and a new > field in struct net_device. > > Reported-by: Andrew Dickinson <andrew@...dna.net> > Signed-off-by: Eric Dumazet <dada1@...mosbay.com> Applied, except that I changed the commit message header line to more reflect that this is in fact a bug fix. BTW, you don't need the reciprocol when num-tx-queues <= num-rx-queues (you can just use the RX queue recording as the hash, straight) and that's the kind of check what I intended to add to net-2.6 had you not beaten me to this patch. Also, thanks for giving me absolutely no credit for this whole thing in your commit message. I know I do that to you all the time :-/ How can you forget so quickly that I'm the one that even suggested the exact code change for Andrew to test in the first place? -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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