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From Rainer Jung <>
Subject Re: Serious mod_jk performance issue
Date Wed, 13 Dec 2006 07:20:52 GMT
If noone finds a reason for it, I can go into it during the weekend. I
would try to reproduce and research on Solaris. Concerning your data for
Solaris: Apache and Tomcat were both on Solaris? The same machine or
different? Network between Client (Browser?) and Apache was 100MBit or



Jess Holle schrieb:
> We're seeing a *serious *performance issue with mod_jk and large (e.g.
> 500MB+) file transfers.  [This is with Apache 2.0.55, Tomcat 5.0.30, and
> various recent mod_jk including 1.2.20.]
> The performance of downloading the file via Apache is good, as is the
> performance when downloading directly from Tomcat.  The performance when
> downloading from Tomcat through Apache via mod_jk is, however, quite
> abysmal.  I'd obviously expect *some* degradation due to the extra
> interprocess hop, but given that this is a just a single-user,
> single-request test, I'd expect that the network would still be the
> limiting factor -- or at least that the degradation would be in the
> order of 25% of less.  What we're seeing, however, is far worse:
>    On Windows:
>        * Apache 2.0.55, Tomcat 5.0.30, and mod_jk 1.2.20 - Started at
>          10 MB/sec ended at 3 MB/sec with mod_deflate disabled (1.5
>          MB/sec with mod_deflate enabled)
>        * Apache 2.0.55, Tomcat 5.0.30, and mod_jk 1.2.19 - Disabling
>          JkFlushPackets only slightly improved performance.
>        * Apache 2.2.3 with Tomcat 5.5.20 w/ the native connector -
>          Didn't work period.  I didn't have a chance to look into it,
>          but the download failed after getting serveral packets (!)
>        * Apache 2.2.3 with Tomcat 5.5.20 w/o the native connector - Was
>          only slightly slower than going straight through Apache
>          about 7-8 MB/sec
>    On Solaris:
>        * Apache 2.0.55, Tomcat 5.0.30, recent mod_jk - Fairly constant
>          4MB/s when going through mod_jk, 10MB/s when just downloading
>          via Apache
>    [This issue originally was thought to be Windows specific, which is
>    why we have many more results for Windows.]
> Obviously if our end goal was simple static file transfers we'd just
> share/mirror them to Apache to solve this (we need the load balancing
> flexibility, etc, of mod_jk, so directly using Tomcat is not really an
> option -- nor is doing non-AJP-proxying).  The static file case is the
> simplified reproduction of our real issue, however, which is large file
> downloads from our (Java-based) content store.
> We had much better results with Apache 2.2.3 and Tomcat 5.5.20 with
> tcnative, but we really don't want to force a move to 2.2.x and Tomcat
> 5.5.x in this case and we've had issues with tcnative (which we *hope*
> may be resolved with 1.1.8).  Overall we'd much prefer to get mod_jk
> working reasonably than to force a disruptive move to 2.2.x right now.
> Is this a known issue?  Any pointers as to where/how to look for the
> performance bottleneck?  Some VTune examination showed that almost all
> of Apache's CPU time during this time was in libapr.dll, but that's
> obviously not terribly specific.
> -- 
> Jess Holle

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