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From apacheuser...@aim.com
Subject Re: [users@httpd] mod_mem_cache question...
Date Sat, 02 Sep 2006 02:19:44 GMT
 Thanks Joshua for the quick reply. Guess this means using mod_mem_cache will not give me the
best cache hit/miss ratio as compared to mod_disk_cache ?
 
 Is the way I have configured apache wrong ? Is it possible to run only 1 instance of httpd
on a box to maximize the cache hit/miss ratio ? Would this approach cause other problems ?
Is there any other MPM I should look at ?
 
 I will look into mod_disk_cache as well..but can you please help me with the above questions...Thanks
in advance...
 
    
 -----Original Message-----
 From: joshua@slive.ca
 To: users@httpd.apache.org
 Sent: Fri, 1 Sep 2006 6:55 PM
 Subject: Re: [users@httpd] mod_mem_cache question...
 
  On 9/1/06, apacheuser123@aim.com <apacheuser123@aim.com> wrote: 
 > 
 > 
 > Hi, 
 > 
 > I have an Apache 2.2.2 setup on a Redhat box. Caching is implemented using 
 > mod_mem_cache. 
 > Apache was built to use worker MPM. Here are the relevant sections from 
 > httpd.conf 
 > 
 > # 
 > # mod_cache/mod_mem_cache settings 
 > # 
 > <IfModule cache_module> 
 > <IfModule mem_cache_module> 
 > CacheEnable mem / 
 > CacheStoreNoStore On 
 > MCacheSize 4096 
 > MCacheMaxObjectCount 200 
 > MCacheMinObjectSize 1 
 > MCacheMaxObjectSize 524288 
 > </IfModule> 
 > </IfModule> 
 > 
 > # 
 > # Worker MPM settings 
 > # 
 > <IfModule mpm_worker_module> 
 > StartServers 1 
 > MaxClients 250 
 > ThreadsPerChild 50 
 > MinSpareThreads 25 
 > MaxSpareThreads 75 
 > </IfModule> 
 > 
 > When I startup Apache, I notice there are multiple httpd( 1 parent and 2 
 > child ) instances. 
 > Question I had is, 
 > 
 > 1. Does this mean that at any time there are could be multiple memory 
 > caches equal to the number of running 
 > httpd instances ? or is the cache somehow shared between child processes ? 
 
 Yes, there is a separate cache for each child process. 
 
 > 
 > 2. How are requests handled ? For instance, do all requests go the first 
 > child process, till it has no 
 > more free threads at which point the the second child process is called 
 > into action ? 
 
 The allocation is essentially random depending on who is holding the 
 accept mutex. 
 
 You should really consider using mod_disk_cache instead. It uses a 
 cache that is shared between all processes, and is often as fast or 
 faster than mod_mem_cache because the OS can optimize the memory 
 caching part. 
 
 Joshua. 
 
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