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Date: Sun, 28 Sep 2014 22:08:43 -0700 From: Alexei Starovoitov <ast@...mgrid.com> To: Eric Dumazet <eric.dumazet@...il.com> Cc: Or Gerlitz <gerlitz.or@...il.com>, "David S. Miller" <davem@...emloft.net>, Jesper Dangaard Brouer <brouer@...hat.com>, Eric Dumazet <edumazet@...gle.com>, John Fastabend <john.r.fastabend@...el.com>, Linux Netdev List <netdev@...r.kernel.org>, Amir Vadai <amirv@...lanox.com>, Or Gerlitz <or.gerlitz@...il.com> Subject: Re: [PATCH net-next] mlx4: optimize xmit path On Sun, Sep 28, 2014 at 7:22 PM, Eric Dumazet <eric.dumazet@...il.com> wrote: > On Sun, 2014-09-28 at 13:49 -0700, Alexei Starovoitov wrote: > >> I see. So xmit_more=true overrides blueflame=on settings. > > Yes, unless Mellanox folks have another way. > >> I wonder what is the performance difference bf=on vs bf=off, >> also whether a burst of N packets via bf is slower than >> burst via queue+doorbell. >> Some fun exploration for driver experts :) > > Prior situation : bf=on : ~4.5 Mpps > > queue + doorbell every 8 packets : ~8 Mpps, up to 10Mpps if tuned > properly. > > Rewritten mlx4 tx path and no burst (bf=on doorbell at every packet) : > 5.3 Mpps > > With the full mlx4 patch and burst = 8 -> 14.9 Mpps > > This is on a 40Gb NIC, with 108 bytes packets. > > (Using <= 104 bytes packets actually gives lower pps because of > 'inlining' done by the driver : 8 Mpps for PKTSIZE=40 ) > > # cat /sys/module/mlx4_en/parameters/inline_thold > 104 nice. Understood. All makes sense. I'm not sure whether it's worth to break it down into small pieces. Imo it's good to go as-is. 'inlining' tuning can come later. Thanks again! -- 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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