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From Yongming Zhao <ming....@gmail.com>
Subject Re: 3.3.5: performance regression?
Date Sat, 10 Aug 2013 16:09:08 GMT

在 2013-8-10,下午11:41,Reindl Harald <h.reindl@thelounge.net> 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.



>> please compare the Origin Side traffic during the test
> 
> the origin is 127.0.0.1:80 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.


> 
>> 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.


> 
>> 在 2013-8-10,下午11:14,Reindl Harald <h.reindl@thelounge.net> 写道:
>> 
>>> 
>>> Am 10.08.2013 16:46, schrieb Leif Hedstrom:
>>>> On Aug 10, 2013, at 7:21 AM, Reindl Harald <h.reindl@thelounge.net>
wrote:
>>>> 
>>>>> has anybody compared 3.2 / 3.3 in performance?
>>>>> 
>>>>> ab -c 200 -n 100000 http://<url>/rte/upload/logo.gif while "logo.gif"
is
>>>>> 643 bytes small and currently httpd without Trafficserver in front has
>>>>> nearly the same perfomrance with even lower CPU
>>>> 
>>>> I haven't seen this behavior. Are you positive the 3.3.5 results are cache
hits ? And if so, that they become RAM cache hits? Just trying to get some ideas here …
:)
>>> 
>>> i hope so, if not that would be a bug
>>> 
>>> [root@testserver:~]$ curl --head http://rhsoft.testserver/rte/upload/logo.gif
>>> HTTP/1.1 200 OK
>>> Date: Sat, 10 Aug 2013 15:09:31 GMT
>>> Last-Modified: Tue, 11 Apr 2006 10:40:40 GMT
>>> ETag: "283-411255ab33a00"
>>> Accept-Ranges: bytes
>>> Content-Length: 643
>>> Cache-Control: max-age=60
>>> Expires: Sat, 10 Aug 2013 15:10:31 GMT
>>> X-Content-Type-Options: nosniff
>>> Connection: close
>>> Content-Type: image/gif
>>> 
>>> on the origin mod_expires is in action to set 60 seconds
>>> cache for images because in our case we have 100% dynamic
>>> pages and the job of ATS is only hold back the image/css/js
>>> requests from the preforking apache and offer KeepAlive
>>> 
>>> the 60 seconds are reflected in the curl-repsonse abvove
>>> which comes from the origin (127.0.0.1:80)
>>> 
>>> <IfModule mod_expires.c>
>>> ExpiresActive On
>>> ExpiresByType image/jpeg A60
>>> ExpiresByType image/jpg A60
>>> ExpiresByType image/gif A60
>>> ExpiresByType image/png A60
>>> ExpiresByType text/css A60
>>> ExpiresByType text/html A60
>>> ExpiresByType text/javascript A60
>>> ExpiresByType text/comma-separated-values A60
>>> ExpiresByType text/tab-separated-values A60
>>> ExpiresByType application/javascript A60
>>> ExpiresByType application/x-javascript A60
>>> ExpiresByType application/xhtml+xml A60
>>> ExpiresByType application/xml A60
>>> <IfModule/>
>>> 
>>> 
>>>> Reclaimable freelist would not have these sort of performance discrepancies
>>> 
>>> yes, and it should not matter in a (ok small) cache with only a handful of objects
> 


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