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From "Vincent Bray" <>
Subject Avoiding mem_cache assumptions
Date Wed, 22 Aug 2007 18:33:21 GMT

It's a common misconception that because mem_cache uses 'memory'
rather disk_cache using 'disk', that one should assume the former is
somehow faster.

Documenting this misconception is fraught with not wanting to say
"this sucks", so let's not say that. How about:

Index: docs/manual/mod/mod_mem_cache.xml
--- docs/manual/mod/mod_mem_cache.xml   (revision 567358)
+++ docs/manual/mod/mod_mem_cache.xml   (working copy)
@@ -41,6 +41,11 @@

     <p>Content is stored in and retrieved from the cache using URI based
     keys. Content with access protection is not cached.</p>
+    <note><title>Note</title>Don't assume that because this module caches
+    memory it is faster than <module>mod_disk_cache</module>. Modern virtual
+    memory systems can make delivery from disk more efficient using
kernel level
+    <code>sendfile()</code> support.</note>

(I should note that this 'patch' is an addition to the <summary> atop

There are of course other issue related to per-worker caches in
mem_cache, but I don't know sendfile() from sendelbow(), so this is
the best I could come up with.

I'm not terribly diplomatic at the best of times, so is there a better
way to suggest that users try disk_cache first?


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