On 2013-02-06 06:56, Sorin Srbu wrote:
>> From: Les Mikesell [mailto:lesmikesell AT gmail DOT com]
>> You are testing sustained transfer times there.  The killer with small
>> files is the seek time while the disk head bounces around reading
>> little bits of directory and inode data.    And once you get started,
>> the server has to do approximately the same to check for matches -
>> possibly with other backups running.
> 
> I realized that afterwards. I'll be looking for some kind of random test 
> instead.

No, this is what you want:

/usr/bin/time -v find /home -mtime 1 >/dev/null

This will generate a list of all files in /home, checking each of their
modification times, and throw all the output away. This performs a total
directory traversal where each file's inode is checked. This is almost
certainly the limiting factor of your rsync.

The above spits out a lot of output. You are interested in "User time" (CPU
time in userspace) and "Elapsed (wall clock) time". Example from my PC:

tyler@baal:~$ /usr/bin/time -v find /home -mtime 1 >/dev/null
        Command being timed: "find /home -mtime 1"
        User time (seconds): 0.14
        System time (seconds): 0.96
        Percent of CPU this job got: 15%
        Elapsed (wall clock) time (h:mm:ss or m:ss): 0:07.07
        Average shared text size (kbytes): 0
        Average unshared data size (kbytes): 0
        Average stack size (kbytes): 0
        Average total size (kbytes): 0
        Maximum resident set size (kbytes): 2320
        Average resident set size (kbytes): 0
        Major (requiring I/O) page faults: 0
        Minor (reclaiming a frame) page faults: 1512
        Voluntary context switches: 2398
        Involuntary context switches: 196
        Swaps: 0
        File system inputs: 31000
        File system outputs: 0
        Socket messages sent: 0
        Socket messages received: 0
        Signals delivered: 0
        Page size (bytes): 4096
        Exit status: 0

Directory and inode data is cached by the kernel so subsequent runs are
faster. You can tune these with sysctl:

vm.swappiness
vm.vfs_cache_pressure

More information (shameless use of my blog):

http://www.tolaris.com/2008/09/28/making-the-gui-faster-in-ubuntu-linux/

Regards,
Tyler

-- 
"There is no 'eastern' and 'western' medicine. There's 'medicine' and
then there's 'stuff that has not been proven to work.'"
   -- Maki Naro, "The Red Flags of Quackery, v2.0", Sci-ence.org

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