While it's possible the default credits (8 as I recall) is not enough for peak performance, it seems to me that something else is wrong: Each 1MB RPC should take ~300uS (based on MPI/IB xfer rates of 3.2+ GB/s), so that means there is another 400uS overhead per RPC that is not masked with 8 concurrent RPCs, in addition to the overhead masked when he increased concurrency. This is crazy, with a 1uS network latency.
Unless the RPCs are are being broken into tiny chunks or something -- does lnet do single-page xfers and not use a rendezvous protocol for full-sized RPCs? It definitely seems that something is broken when o2iblnd gets ~1/3 of the MPI BW, given that lnd was designed for high-speed xfers. The max_rpcs_in_flight normally needs tweaking to improve disk concurrency, where a single client needs to drive a high queue depth. Still finding it hard to believe 8 1MB concurrent RPCs can't handle the network. Kevin On Feb 20, 2012, at 5:44 PM, "Jeremy Filizetti" <<mailto:[email protected]><mailto:[email protected]>[email protected]<mailto:[email protected]>> wrote: Am I reading your earlier post correctly that you have a single server acting as the MDS and OSS? Have you changed your peer_credits and credits for ko2iblnd kernel module on the server and client? You also mentioned changing osc.*.max_dirty_mb, you probably need to adjust osc.*.max_rpcs_in_flight as well. Can you post your rpc stats "lctl get_param osc.*.rpc_stats"? I would guess they are bunching up around 7-8 if your running with the default max_rpcs_in_flight=8. Jeremy On Mon, Feb 20, 2012 at 4:59 PM, Barberi, Carl E <<mailto:[email protected]><mailto:[email protected]><mailto:[email protected]>[email protected]<mailto:[email protected]>> wrote: Thank you. This did help. With the concurrency set to 16, I was able to get a max write speed of 1138 MB/s. Any ideas on how we can make that faster, though? Ideally, we’d like to get to 1.5 GB/s. Carl From: Liang Zhen [mailto:<mailto:[email protected]><mailto:[email protected]><mailto:[email protected]>[email protected]<mailto:[email protected]>] Sent: Thursday, February 16, 2012 1:45 AM To: Barberi, Carl E Cc: '<mailto:[email protected]><mailto:[email protected]><mailto:[email protected]>[email protected]<mailto:[email protected]>' Subject: EXTERNAL: Re: [Lustre-discuss] LNET Performance Issue Hi, I assume you are using "size=1M" for brw test right? performance could increase if you set "concurrency" while adding brw test, i.e: --concurrency=16 Liang On Feb 16, 2012, at 3:30 AM, Barberi, Carl E wrote: We are having issues with LNET performance over Infiniband. We have a configuration with a single MDT and six (6) OSTs. The Lustre client I am using to test is configured to use 6 stripes (lfs setstripe -c 6 /mnt/lustre). When I perform a test using the following command: dd if=/dev/zero of=/mnt/lustre/test.dat bs=1M count=2000 I typically get a write rate of about 815 MB/s, and we never exceed 848 MB/s. When I run obdfilter-survey, we easily get about 3-4GB/s write speed, but when I run a series of lnet-selftests, the read and write rates range from 850MB/s – 875MB/s max. I have performed the following optimizations to increase the data rate: On the Client: lctl set_param osc.*.checksums=0 lctl set_param osc.*.max_dirty_mb=256 On the OSTs lctl set_param obdfilter.*.writethrough_cache_enable=0 lctl set_param obdfilter.*.read_cache_enable=0 echo 4096 > /sys/block/<devices>/queue/nr_requests I have also loaded the ib_sdp module, which also brought an increase in speed. However, we need to be able to record at no less than 1GB/s, which we cannot achieve right now. Any thoughts on how I can optimize LNET, which clearly seems to be the bottleneck? Thank you for any help you can provide, Carl Barberi _______________________________________________ Lustre-discuss mailing list <mailto:[email protected]><mailto:[email protected]><mailto:[email protected]>[email protected]<mailto:[email protected]> <http://lists.lustre.org/mailman/listinfo/lustre-discuss><http://lists.lustre.org/mailman/listinfo/lustre-discuss><http://lists.lustre.org/mailman/listinfo/lustre-discuss>http://lists.lustre.org/mailman/listinfo/lustre-discuss _______________________________________________ Lustre-discuss mailing list <mailto:[email protected]><mailto:[email protected]><mailto:[email protected]>[email protected]<mailto:[email protected]> <http://lists.lustre.org/mailman/listinfo/lustre-discuss><http://lists.lustre.org/mailman/listinfo/lustre-discuss><http://lists.lustre.org/mailman/listinfo/lustre-discuss>http://lists.lustre.org/mailman/listinfo/lustre-discuss _______________________________________________ Lustre-discuss mailing list <mailto:[email protected]><mailto:[email protected]>[email protected]<mailto:[email protected]> <http://lists.lustre.org/mailman/listinfo/lustre-discuss><http://lists.lustre.org/mailman/listinfo/lustre-discuss>http://lists.lustre.org/mailman/listinfo/lustre-discuss Confidentiality Notice: This e-mail message, its contents and any attachments to it are confidential to the intended recipient, and may contain information that is privileged and/or exempt from disclosure under applicable law. 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