[stgt] Worker Threads

GProcunier at symcor.com GProcunier at symcor.com
Mon Sep 26 22:20:22 CEST 2011


Our network is 10Gbit end to end not 1Gbit as you mentioned earlier.

Regarding latency, I personally feel something is off with what the UCS 
network cards are rated for and what Linux ends up showing:

[root at storage02 mnt]# ping
PING ( 56(84) bytes of data.
64 bytes from icmp_seq=1 ttl=64 time=0.185 ms
64 bytes from icmp_seq=2 ttl=64 time=0.156 ms
64 bytes from icmp_seq=3 ttl=64 time=0.158 ms
64 bytes from icmp_seq=4 ttl=64 time=0.154 ms
64 bytes from icmp_seq=5 ttl=64 time=0.151 ms
64 bytes from icmp_seq=6 ttl=64 time=0.153 ms
--- ping statistics ---
6 packets transmitted, 6 received, 0% packet loss, time 5429ms
rtt min/avg/max/mdev = 0.151/0.159/0.185/0.017 ms

(More relevant) 

[root at storage02 ~]# netperf -H -t TCP_SENDFILE  -F 100M -C -c 
-l 60  -- -m 16M -s 16M -S 16M
TCP SENDFILE TEST from ( port 0 AF_INET to 
( port 0 AF_INET
Recv   Send    Send                          Utilization       Service 
Socket Socket  Message  Elapsed              Send     Recv     Send Recv
Size   Size    Size     Time     Throughput  local    remote   local 
bytes  bytes   bytes    secs.    10^6bits/s  % S      % S      us/KB us/KB

33554432 33554432 16777216    60.03      9259.27   1.14     3.27     0.242 

[root at storage02 ~]# modinfo enic
license:        GPL
author:         Scott Feldman <scofeldm at cisco.com>
description:    Cisco VIC Ethernet NIC Driver
srcversion:     EB6B26B5EEA5A1C378A1BD6
alias:          pci:v00001137d00000044sv*sd*bc*sc*i*
alias:          pci:v00001137d00000043sv*sd*bc*sc*i*
vermagic:       2.6.32-131.0.15.el6.x86_64 SMP mod_unload modversions 

Reading the product specs for this card, it is rated for 10-12 us, yet we 
are seeing latency of 180us+, thoughts ?  Does anyone else on a 10Gbit 
local network experience this kind of latency ?

Is there a general rule of thumb to determine how latency is going to 
affect IO with iSCSI ?


Greg Procunier
UNIX Administrator III - Enterprise Servers and Storage
1 Robert Speck Parkway, Suite 400, Mississauga, Ontario L4Z 4E7
Office: 416-673-3320 
Mobile: 647-895-2977
Email: gprocunier at symcor.com

"Bennett, Jeffrey" <jab at sdsc.edu> wrote on 09/26/2011 04:11:15 PM:

> From: "Bennett, Jeffrey" <jab at sdsc.edu>
> To: "GProcunier at symcor.com" <GProcunier at symcor.com>, FUJITA Tomonori
> <fujita.tomonori at lab.ntt.co.jp>
> Cc: "agrover at redhat.com" <agrover at redhat.com>, 
> "fujita.tomonori at lab.ntt.co.jp" <fujita.tomonori at lab.ntt.co.jp>, 
> "stgt at vger.kernel.org" <stgt at vger.kernel.org>, "stgt-
> owner at vger.kernel.org" <stgt-owner at vger.kernel.org>
> Date: 09/26/2011 04:11 PM
> Subject: RE: Worker Threads
> Thanks Greg, you did a great job documenting all of your testing.
> We have noticed a great improvement in random performance (4kb 
> blocksize) over iSER when using 128 worker threads in comparison 
> with 4 worker threads. I don't have the numbers in front of me but 
> something around 200.000 random read IOPS and 4GB/sec is what we see
> in our system using 16 flash drives and QDR IB.
> It seems you are using 1Gbit network so maybe in your particular 
> case, given the latency of Ethernet-based network, increasing the 
> worker threads does not help with random i/o, even when using a ramdisk.
> jab
> -----Original Message-----
> From: GProcunier at symcor.com [mailto:GProcunier at symcor.com] 
> Sent: Monday, September 26, 2011 1:02 PM
> To: FUJITA Tomonori
> Cc: agrover at redhat.com; fujita.tomonori at lab.ntt.co.jp; Bennett, 
> Jeffrey; stgt at vger.kernel.org; stgt-owner at vger.kernel.org
> Subject: Re: Worker Threads
> Few additional things.
> 1) my apologies, lotus notes is the devil and did all sorts of 
> terrible things to the formatting of initial post when viewed on 
> http://lists.wpkg.org/pipermail/stgt/2011-September/004782.html
> 2) I have yet to see anyone post a detailed setup / results showing 
> 1000+ MB/s throughput between open-iSCSI and stgt, so hopefully this
> helps people.
> 3) I am surprised the iops are so low for small block tests, kind of
> makes you wonder about the validity of the splash page of http://
> www.open-iscsi.org/ which boasts 50k+ iops with small block sizes. 
> Using a ramdisk eliminates the storage as a contention point so 
> really all that is left is the initiator and the target.
> 4) tgt-admin needs some serious updating/work/rewrite, missing many 
> flags / cant add nullio devices via it etc etc.  My patch for 
> bsflags is the tip of the iceberg as far as problems with that tool.
> Cheers,
> --
> Greg Procunier
> UNIX Administrator III - Enterprise Servers and Storage
> 1 Robert Speck Parkway, Suite 400, Mississauga, Ontario L4Z 4E7
> Office: 416-673-3320
> Mobile: 647-895-2977
> Email: gprocunier at symcor.com
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 10.0.1410 / Virus Database: 1520/3920 - Release Date: 09/26/11

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