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From Leif Hedstrom <>
Subject Re: Need some help tuning for large file performance
Date Fri, 17 Sep 2010 02:57:57 GMT
  On 09/16/2010 08:09 PM, Pranav Desai wrote:
> On
> Done. Using 2 disks. Do you recommend a raid config for better performance ?

No, I recommend RAID only if you really, really care for redundancy / 
reliability. ATS will automatically "load balance" across any disks that 
you throw at it.

> Here are my tcp mem parameters. And req/sec isnt of concern here so I
> should be ok with the listen queue and backlogs. If you have any
> particular setting in mind please let me know.
> net.ipv4.tcp_mem = 1339776      1786368 2679552
> net.ipv4.tcp_wmem = 4096        87380   8388608
> net.ipv4.tcp_rmem = 4096        87380   8388608

These would only make a difference if there's a latency between the 
client and the server (which is generally not the case in a "lab").  The 
above are for the autoscaling window sizes I think, which seem 
reasonable. There are settings in records.config to bump up the initial 
window size for the connections:


You definitely want to tune that mmap setting I mentioned earlier, and a 
few other interesting sysctl's would be

     net.ipv4.tcp_max_syn_backlog (set it pretty high)
     net.ipv4.tcp_syncookies (enable it)
     net.ipv4.tcp_ecn (probably want it disabled)
     net.ipv4.tcp_max_tw_buckets (increase for lots of sockets I think)

> I think I can reproduce it but under load, so it might be a bit
> difficult to debug it especially with all the threads. I will try to
> get to a simpler test case to reproduce it. Maybe I can run
> traffic_server alone with a single network and io thread ? How do you
> guys normally debug it ?

I think we should move the discussions related to this crasher problem 
to the mailing list (information how to 
subscribe to it is on There's a wider 
crowd there that might be able to help as well, in particular John 
Plevyak knows the cache better than anyone else on the planet.

That much said, if you can reproduce it with restrictions like you 
mention, that'll certainly help. Or, just describe how to setup the 
environment, and what "load" to send to it, that might also help. But 
the more you can limit the parameters / tests / time necessary to 
reproduce it, the better.


-- leif

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