| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Fri, 3 Dec 2010 22:38:00 +0900 From: Simon Horman <horms@...ge.net.au> To: Eric Dumazet <eric.dumazet@...il.com> Cc: Ben Hutchings <bhutchings@...arflare.com>, netdev@...r.kernel.org Subject: Re: Bonding, GRO and tcp_reordering On Wed, Dec 01, 2010 at 01:34:45PM +0900, Simon Horman wrote: > On Tue, Nov 30, 2010 at 05:04:33PM +0100, Eric Dumazet wrote: > > Le mardi 30 novembre 2010 à 15:42 +0000, Ben Hutchings a écrit : > > > On Tue, 2010-11-30 at 22:55 +0900, Simon Horman wrote: To clarify my statement in a previous email that GSO had no effect: I re-ran the tests and I still haven't observed any affect of GSO on my results. However, I did notice that in order for GRO on the server to have effect I also need TSO enabled on the client. I thought that I had previously checked that but I was mistaken. Enabling TSO on the client while leaving GSO disabled on the server resulted in increased CPU utilisation on the client, from ~15% to ~20%. > > > > The only other parameter that seemed to have significant effect was to > > > > increase the mtu. In the case of MTU=9000, GRO seemed to have a negative > > > > impact on throughput, though a significant positive effect on CPU > > > > utilisation. > > > [...] > > > > > > Increasing MTU also increases the interval between packets on a TCP flow > > > using maximum segment size so that it is more likely to exceed the > > > difference in delay. > > > > > > > GRO really is operational _if_ we receive in same NAPI run several > > packets for the same flow. > > > > As soon as we exit NAPI mode, GRO packets are flushed. > > > > Big MTU --> bigger delays between packets, so big chance that GRO cannot > > trigger at all, since NAPI runs for one packet only. > > > > One possibility with big MTU is to tweak "ethtool -c eth0" params > > rx-usecs: 20 > > rx-frames: 5 > > rx-usecs-irq: 0 > > rx-frames-irq: 5 > > so that "rx-usecs" is bigger than the delay between two MTU full sized > > packets. > > > > Gigabit speed means 1 nano second per bit, and MTU=9000 means 72 us > > delay between packets. > > > > So try : > > > > ethtool -C eth0 rx-usecs 100 > > > > to get chance that several packets are delivered at once by NIC. > > > > Unfortunately, this also add some latency, so it helps bulk transferts, > > and slowdown interactive traffic > > Thanks Eric, > > I was tweaking those values recently for some latency tuning > but I didn't think of them in relation to last night's tests. > > In terms of my measurements, its just benchmarking at this stage. > So a trade-off between throughput and latency is acceptable, so long > as I remember to measure what it is. Thanks, rx-usecs was set to 3 and changing it to 15 on the server did seem increase throughput with 1500 byte packets. Although CPU utilisation increased too, disproportionally so on the client. MTU=1500, client,server:tcp_reordering=3, client:GSO=off, client:TSO=on, server:GRO=off, server:rx-usecs=3(default) # netperf -c -4 -t TCP_STREAM -H 172.17.60.216 TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 172.17.60.216 (172.17.60.216) port 0 AF_INET Recv Send Send Utilization Service Demand Socket Socket Message Elapsed Send Recv Send Recv Size Size Size Time Throughput local remote local remote bytes bytes bytes secs. 10^6bits/s % S % U us/KB us/KB 87380 16384 16384 10.00 1591.34 16.35 5.80 1.683 2.390 MTU=1500, client,server:tcp_reordering=3(default), client:GSO=off, client:TSO=on, server:GRO=off server:rx-usecs=15 # netperf -c -4 -t TCP_STREAM -H 172.17.60.216 TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 172.17.60.216 (172.17.60.216) port 0 AF_INET Recv Send Send Utilization Service Demand Socket Socket Message Elapsed Send Recv Send Recv Size Size Size Time Throughput local remote local remote bytes bytes bytes secs. 10^6bits/s % S % U us/KB us/KB 87380 16384 16384 10.00 1774.38 23.75 7.58 2.193 2.801 I also saw an improvement with GRO enabled on the server and TSO enabled on the client. Although in this case I found rx-usecs=45 to be the best value. MTU=1500, client,server:tcp_reordering=3(default), client:GSO=off, client:TSO=on, server:GRO=on server:rx-usecs=3(default) # netperf -c -4 -t TCP_STREAM -H 172.17.60.216 TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 172.17.60.216 (172.17.60.216) port 0 AF_INET Recv Send Send Utilization Service Demand Socket Socket Message Elapsed Send Recv Send Recv Size Size Size Time Throughput local remote local remote bytes bytes bytes secs. 10^6bits/s % S % U us/KB us/KB 87380 16384 16384 10.00 2553.27 13.31 3.35 0.854 0.860 MTU=1500, client,server:tcp_reordering=3(default), client:GSO=off, client:TSO=on, server:GRO=on server:rx-usecs=45 # netperf -c -4 -t TCP_STREAM -H 172.17.60.216 TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 172.17.60.216 (172.17.60.216) port 0 AF_INET Recv Send Send Utilization Service Demand Socket Socket Message Elapsed Send Recv Send Recv Size Size Size Time Throughput local remote local remote bytes bytes bytes secs. 10^6bits/s % S % U us/KB us/KB 87380 16384 16384 10.00 2727.53 29.45 9.48 1.769 2.278 I did not observe any improvement in throughput when increasing rx-usecs from 3 when using mtu=9000 although there was a slight increase in CPU utilisation (maybe, there is quite a lot of noise in the results). -- 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
Powered by blists - more mailing lists