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Message-ID: <4EDE5D09.1060404@hp.com> Date: Tue, 06 Dec 2011 10:20:57 -0800 From: Rick Jones <rick.jones2@...com> To: "John A. Sullivan III" <jsullivan@...nsourcedevel.com> CC: Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org Subject: Re: Latency difference between fifo and pfifo_fast On 12/06/2011 12:51 AM, Eric Dumazet wrote: > Le mardi 06 décembre 2011 à 03:39 -0500, John A. Sullivan III a écrit : > >>> ifconfig eth2 txqueuelen 0 >>> tc qdisc add dev eth2 root pfifo >>> tc qdisc del dev eth2 root >>> >>> >>> >>> >> Really? I didn't know one could do that. Thanks. However, with no >> queue length, do I have a significant risk of dropping packets? To >> answer your other response's question, these are Intel quad port e1000 >> cards. We are frequently pushing them to near line speed so >> 1,000,000,000 / 1534 / 8 = 81,486 pps - John > > You can remove qdisc layer, since NIC itself has a TX ring queue > > (check exact value with ethtool -g ethX) > > # ethtool -g eth2 > Ring parameters for eth2: > Pre-set maximums: > RX: 4078 > RX Mini: 0 > RX Jumbo: 0 > TX: 4078 > Current hardware settings: > RX: 254 > RX Mini: 0 > RX Jumbo: 0 > TX: 4078 ---- HERE ---- And while you are down at the NIC, if every microsecond is precious (no matter how close to epsilon compared to the latencies of spinning rust :) you might consider disabling interrupt coalescing via ethtool -C. rick jones -- 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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