[HTTPS-Everywhere] Startup time measurements in Chrome and Firefox

[Peter Eckersley]

On Fri, Jan 17, 2014 at 08:01:40PM -0800, Mike Perry wrote:
> 
> > We should measure this.  But we should definitely measure it in the case
> > where the entire sqlite file is in the OS page cache, so in TBB we
> > should /definitely/ read and discard its entire contents before playing.
> 
> Yes. Having solid numbers here would make me feel better about this.
>

So I have implemented some performance tests in the sqlite branch of my
github remote:

https://github.com/pde/https-everywhere/commits/sqlite

They operate by asking potentiallyApplicableRulesets() for each of the
Alexa top 10K domains, measuring overall ellapsed time, then doing it
again.  

Here's what I see:

Calling potentiallyApplicableRulesets() with 10000 domains
1088 hits: average call to potentiallyApplicableRulesets took 0.157 milliseconds
1088 hits: average subsequent call to potentiallyApplicableRulesets took 0.0513 milliseconds

So wrt Mike's fingerprinting concern, subsequent calls to
potentiallyApplicableRulesets() are 3x faster (and will be more so if we
put in the LRU cache) but the measurable difference is only a tenth of a
millisecond, which will be hard to exploit given that this is over the
top of the Tor network and repetitive measurement is impossible.

Along the way I noticed the very weird phenomenon that unless I prepend
"www." to the test domains I only get a handful of hits, more like 20
than 1088.  This makes me think that either there are lots and lots of
rulesets that target *.example.com and not example.com, or there's a bug
in the sqlite patch somewhere...

-- 
Peter Eckersley                            pde at eff.org
Technology Projects Director      Tel  +1 415 436 9333 x131
Electronic Frontier Foundation    Fax  +1 415 436 9993