[Lustre-discuss] LNET Performance Issue

[Liang Zhen]

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
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