[zeromq-dev] zeromq performance

Charles Remes lists at chuckremes.com
Sat Jun 7 18:55:00 CEST 2014


This is a very interesting result. It’s probably worthwhile to add this to the FAQ.

It would be interesting to test this scenario with the ZMQ_AFFINITY option for zmq_setsockopt. If you have a chance, could you let us know if setting the I/O thread affinity results in a similar performance difference?

cr

On Jun 7, 2014, at 7:44 AM, Paul Phillips <paul at marketgridsystems.com> wrote:

> I have tracked down the source of this “problem”.  It turns out that the running multiple local-remote sets is not the key, it is actually related to what processor core things are running on.  If the local_lat and the remote_lat run on the same core then the comms is very fast (whether ipc or tcp).  If they are on separate cores, the comms is slower.  When I ran multiple sets, it just turned out that for some reason, the second local and remote set would be on the same core.  I can replicate the whole thing using taskset to force local_lat and remote_lat either to different or the same cores.
> 
> I have pasted my results from two runs, the first using separate cores and the second using the same core and the results are very different - 25 micros latency vs 7 micros latency (I have printed a couple of extra things at the end and renamed the executables to xlocal_lat and xremote_lat but they are the same code from the perf directory in the distribution of 4.0.4).
> 
> (MarketGrid)[Paul at CentOS65-Dev tmp]$ taskset -c 0 ./xlocal_lat ipc://testport2 100 100000 &
> [1] 3566
> (MarketGrid)[Paul at CentOS65-Dev tmp]$ taskset -c 1 ./xremote_lat ipc://testport2 100 100000 &
> [2] 3578
> (MarketGrid)[Paul at CentOS65-Dev tmp]$ message size: 100 [B]
> roundtrip count: 100000
> average latency: 25.421 [us]
> elapssed: 5084170
> throughput: 19668
> 
> [1]-  Done                    taskset -c 0 ./xlocal_lat ipc://testport2 100 100000
> [2]+  Done                    taskset -c 1 ./xremote_lat ipc://testport2 100 100000
> (MarketGrid)[Paul at CentOS65-Dev tmp]$ 
> (MarketGrid)[Paul at CentOS65-Dev tmp]$ 
> (MarketGrid)[Paul at CentOS65-Dev tmp]$ taskset -c 0 ./xlocal_lat ipc://testport2 100 100000 &
> [1] 3581
> (MarketGrid)[Paul at CentOS65-Dev tmp]$ taskset -c 0 ./xremote_lat ipc://testport2 100 100000 &
> [2] 3584
> (MarketGrid)[Paul at CentOS65-Dev tmp]$ message size: 100 [B]
> roundtrip count: 100000
> average latency: 7.016 [us]
> elapssed: 1403130
> throughput: 71269
> 
> [1]-  Done                    taskset -c 0 ./xlocal_lat ipc://testport2 100 100000
> [2]+  Done                    taskset -c 0 ./xremote_lat ipc://testport2 100 100000
> (MarketGrid)[Paul at CentOS65-Dev tmp]$ 
> 
> Regards, Paul Phillips
> Director, MarketGrid Systems Pty Ltd
> t: +61 419 048 874
> e: paul at marketgridsystems.com
> 
> 
> 
> On 7 Jun 2014, at 6:17 pm, Pieter Hintjens <ph at imatix.com> wrote:
> 
>> How many messages are you sending? There will be a start-up cost that
>> can be disproportionate if you send only a few messages.
>> 
>> On Sat, Jun 7, 2014 at 6:54 AM, Paul Phillips
>> <paul at marketgridsystems.com> wrote:
>>> Hi.  I have an interesting scenario when testing zeromq 4.0.4 on CentOS 6.5.
>>> When I run local_lat and remote_lat using ipc, I get a latency of around 30
>>> micros.  However, if I run them once in the background with a large round
>>> trips setting (so they keep running for a long time) and then run a second
>>> set, the second set always returns a latency of around 7 micros.  Basically,
>>> once I have one lot of stuff running in the background, subsequent stuff
>>> always seems to run much faster.  Is there any known explanation for this
>>> behaviour?
>>> 
>>> Regards, Paul Phillips
>>> 
>>> Director, MarketGrid Systems Pty Ltd
>>> t: +61 419 048 874
>>> e: paul at marketgridsystems.com
>>> 
>>> 
>>> 
>>> 
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