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From Reindl Harald <>
Subject Re: 3.3.5: performance regression?
Date Sat, 10 Aug 2013 16:15:41 GMT

Am 10.08.2013 18:09, schrieb Yongming Zhao:
> 在 2013-8-10,下午11:41,Reindl Harald <> 写道:
>> Am 10.08.2013 17:32, schrieb Yongming Zhao:
>>> if your requested URL is expires very often, then you may hit the 
>>> read-while-writer performance issue, we have fixed that read-while-writer
>>> in V3.3 that will make it really work.
>> but every 60 seconds is not that often in case of a apache-benchmark
>> it's a simple calculation how many cache-hits you can have within
>> this 60 seconds by 200 parallel requests of the same URL
> we care of the performance, but your case is mixing with the feature 
> of read-while-writer, if you get to know that read-while-writer may 
> affect your performance result, that will help us compare the result, 
> in the better understanding.

CONFIG proxy.config.cache.enable_read_while_writer INT 0
does not change anything

>>> please compare the Origin Side traffic during the test
>> the origin is but 6 prefork-processes
>> while "ab -c 200" is running indicates pretty clear
>> that all the work is ATS
>> [root@testserver:~]$ ps aux | grep httpd | wc -l
>> 6
> I mean, how many requests you get from the origin side during your testing, or hit ratio

*none* which is pretty clear in case of a preforking-httpd

StartServers             3
MinSpareServers          3
MaxSpareServers          5

so the 6 httpd-processes are the master-process and 5 idle workers

>>> and you'd better try the compare without expire issue, to make sure we have 
>>> not make critical regression there.
>> no - if this is a problem now *it is* a critical regression
>> the only reason trafficserver exists in our infrastructure
>> is to buffer high-traffic sites with a lot of images and
>> hold back the image-count multiplied with users requests
>> from teh preforking-apache
> if you want to enable read while writer, that means you care of the origin side traffic,

> and you may need to pay for the performance drop in speed(response time) on the proxy,

> when that url is getting fetched from the origin

please stop to insist in "read while writer"

* disable it does not change anything
* 100000 requests with 200 parallel are done within the 60 seconds expire
* hence we speak about *one* single URL, only *one* object requested and cached

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