487756 - implement text system instrumentation

Status: NEW

(Core :: Graphics: Text, enhancement)

Description

[John Daggett (:jtd)]

Within gfx text code we spend a lot of time determining glyphs used for a particular run of text, it would be good to put in instrumentation that would tell use more about the performance of that system.  

- what's the relative performance of simple vs. complex text?
- what's the relative hit/miss ratio's of our various caches (frame text run, text run word cache, font cache, etc.)?
- what's the relative performance of cached vs. uncached for each given cache and what factors (lang?) affect it?
- how often does font fallback (font group/pref fonts/system fonts) occur?
- for a given set of pages (grouped by lang/country/type), how often does font fallback occur?  what sort of temporal locality do fallback patterns have (i.e. is fallback relatively random or is there a certain consistency to when/how it occurs)?

I'm imaging something that involves DTrace probes where supported, some sort of logging mechanism otherwise.  It would be nice to have a way of recording a sequence of text run creations so that these could be replayed using a standalone tool to measure text system performance.

Comment 1

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

Dunno if it's useful, but I have a super old patch at http://people.mozilla.com/~vladimir/misc/xxxxxx-xpcom-probe-framework where I tried to make a generic cross-platform probe framework.  I think this was pre-dtrace or around the same time, with me wanting dtrace on win32... this could be extended probably to generate dtrace probes where possible maybe.