[Server-devel] testing XS-on-XO

[Martin Langhoff]

On Mon, Jul 20, 2009 at 6:21 AM, Sameer Verma<sverma at sfsu.edu> wrote:
> I'd like to load test Moodle+Pg. Maybe Wen(@SF State) has some scripts to
> load test it? I know he's been working on that for a while now...cc'd.

You can get through a very simple test just by

 - enabling profiling (see the defines in config-dist.php, copy them
to config.php)

 - using ab against the homepage with the cookies "stolen" from
Browse.xo - you'll need 3 cookies IIRC

The performance is bad enough that just hitting a moderately heavy
page (such as the homepage) is a good "canary in the mine". If we can
make that page snappy (without cheating) we're in good shape.

There are a few things to try and benchmark -

 - Is the precompiler working correctly?

 - Is the Pg xlog a major factor? Switch off sync in Pg's
configuration, how much does it improve things?

 - Is contention over the PHP sessions directory a major issue? Try
with hashed directories - how much does it improve? (You need to use
the extra magic parameters in 'session_dir', and use a special config
setting in config.php - $CFG->respectsessionsettings=true IIRC)

Using sar during the tests is a good thing. IIRC, the SD card is on
the USB bus, and we may be swamping the USB channel, or just driving
the CPU crazy with interrupts.

>> How can you tell the type of card?
>
> It says so on the card.

Too easy! Actually, looking at the lables on the 3 cards I have, two
say 'class 6' or 'C6', the 3rd one doesn't say much.

>> The ones I have seem to be "sucks" and "sucks even more" models :-/
>
> Even with a class 6, I wonder how much of a difference it will make. Writing
> to SD cards is slow.

Well, the C6 cards I have aren't particularly fast :-(

cheers,



m
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 martin at laptop.org -- School Server Architect
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