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From Pranav Desai <>
Subject Need some help tuning for large file performance
Date Thu, 16 Sep 2010 23:04:54 GMT

I am running some performance test with large files. As mentioned in
one of the earlier threads I am using curl-loader for testing with
randomization in the URL to stress the cache.

Version: 2.0.1

CONFIG proxy.config.cache.ram_cache.size LLONG 2097152000
CONFIG proxy.config.cache.ram_cache_cutoff LLONG 100048576

/mnt/cache/trafficserver 60368709120
the file is 15MB in size.

2x Intel Xeon Quad Core 2.4GHz, 12GB RAM.

Here are some numbers.

test1	 sessions	 iter	 cache_size/      url                   hitrate
   avg                           throughput
                                          ram	         randomness	 	
     resp. time

Test1	 500	        50	 56GB/2GB	 1	                 99%	 75sec	
Test2	 500	        50	 56GB/2GB	 0-2k	         45%	 200+
Test3	 500	        50	 4GB/2GB	         0-20k	        0.2%	 75sec	

* The url randomness is just a number within that range in the URL.
* There are 500 clients each access the URL 50 times.

* So in the best case scenario with only a single URL, I can get 700+
Mbps and I think I can get more if I use 2 client machines and more
network cards. Currently the testbed is limited to 1Gbps.
* As I can increase the randomness, so essentially there are 2000
unique URLs, the performance drops significantly.
* The third test suggest that if the cache is small the performance is
good. I even tried with 0-2k random value instead of 20k, but the
throughput doesnt drop.
* So it seems like a large cache just kills the performance.
* The other thing I notices was the IOwait on 1 cpu core was 100%, the
others where pretty idle. Shouldnt the IO load be distributed evenly ?
Is using a file based cache killing it ? maybe its using only 1

Leif mentioned in an earlier thread about the threads_per_disk
settings which I didnt know about, I will run some more tests with

I think I am not using the optimal settings. In production I believe
people are using much large caches. So if someone can share what
hardware configuration they use, I would appreciate it. Number of
drives, raid0 raid1 etc. And what kind of performance you are seeing
from the cache.

Thanks for your time.

-- pranav

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