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[bug #23542] Problem with performance, search it's to slow

From: James Youngman
Subject: [bug #23542] Problem with performance, search it's to slow
Date: Thu, 12 Jun 2008 09:17:56 +0000
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20080404 Iceweasel/ (Debian-

Follow-up Comment #2, bug #23542 (project findutils):

Obviously from the timing information you gave, we can see that almost all
the time is used up in I/O wait rather than user or system CPU time.  

Tools that are useful for finding out why your disk I/O are slow include
iostat and strace.   You can use strace for this task like this:

strace -c find /home/xxx/www -newer /home/xxx/flag > /dev/null

The result is a list of system calls with a summary of how much time is spent
in each.   You should read the strace documentation to understand how to
understand the output.

Although you mention that your filesystems are ext3, you don't indicate
whether the "dir_index" feature is both enabled and in use (because you've run
e2fsck -D).   I assume at this point that this will make a huge difference.  

As the anonymous poster said, it's likely that the differences in  runtime
are affected by cache warmth but I would also guess that somethign else is
going on since you didn't indicate there's a pattern to the run-time. 

The fundutils source tarball also builds by default a binary called "oldfind"
which uses a different algorithm.  It might be worth comparing the runtimes of
the two implementations.  

Lastly a point unrelated to findutils.   If you are serving static web
content out of /home/xxx/www, you have a very poor configuration.  Most Unix
filesystems deal badly with very large directories, and you would be wise to
avoid such an arangement.  One wayt of dealing with this issue is to separate
the URI view of your website from the filesystem layout of the HTML content by
using URL rewriting.  This technique will also allow you to maintain URI
stability; see http://www.w3.org/Provider/Style/URI for more information. 


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