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From Justin Erenkrantz <>
Subject mod_cache performance
Date Tue, 03 Aug 2004 10:13:51 GMT
--On Monday, August 2, 2004 2:49 PM -0400 Bill Stoddard <> 

> To get mod_cache/mod_mem_cache (I know little or nothing about
> mod_disk_cache) really performing competatively against best-of-breed caches
> will require bypassing output filters (and prebuilding headers) and possibly

Here's some comparative numbers to chew on.

One client and one server on 100Mbps network (cheapy 100Base-T switch);
50 simulated users hitting 7 URLs 100 times with flood (35,000 requests).

mod_disk_cache: Requests: 35000 Time: 40.91 Req/Sec: 856.78
mod_mem_cache:  Requests: 35000 Time: 54.90 Req/Sec: 637.81
no cache:       Requests: 35000 Time: 54.86 Req/Sec: 638.81
squid:          Requests: 35000 Time: 105.35 Req/Sec: 332.25

mod_disk_cache completely filled out the network at ~50% CPU usage.
    [Can't push through more than ~8MB/sec (~64Mb/sec) without GigE.]
mod_mem_cache filled up the CPU but not the network
    [Poor scaling characteristics.  It goes to 100% CPU with just 5 users!]
No caching was better CPU-wise (less utilization) than mod_mem_cache
    [Still not as good network or CPU-wise as mod_disk_cache]
squid was really inefficient both CPU and network-wise.

The squid numbers *completely* baffle me.  I have to believe I've got 
something stupid configured in squid (or I did something stupid with flood; 
but the network traces and truss output convince me otherwise).  My squid is 
using the default RHEL3 installation (Squid Cache: Version 2.5.STABLE3).

squid and httpd are on the same box - I may try to move squid to another box - 
will see if I have time tomorrow to find a suitable target to move to...

For those playing along at home, I am hitting the following URLs with flood:


HTH.  -- justin

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