676302 - Make mmap file format for xpt files

Status: RESOLVED WONTFIX

(Core :: XPCOM, defect)

Description

[Benjamin Stover (:stechz)]

Reading in typelib files takes around 50 milliseconds every startup on my Nexus S. We could instead make the file format look a lot more like how this data is stored in memory.

Comment 1

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

I think we'd wait on this until remeasuring after the DOM moves off XPConnect, but it might still be worth doing after that.

Comment 2

[(not currently active) Ted Mielczarek]

I thought about this a bit while writing xpt.py. bsmedberg had mentioned a while ago maybe just producing C++ code with structs instead of .xpt files for our built-in typelibs, that could be another option.

Comment 3

[Benjamin Smedberg]

How much of that time is I/O and how much is other things? We aren't going to significantly reduce the I/O by rearranging the data, right?

And yes, I think we could do this more easily by making XPT output structs and just compile them into libxul without trying to touch the XPT format.

Comment 4

[Benjamin Stover (:stechz)]

I don't have data on the I/O time vs CPU time. Autogenerating the files sounds like the best route to me though.

Comment 5

[Andrew McCreight [:mccr8] (PTO until 12-2)]

At this point, we're more likely to generate structs instead of messing with anything about how the current XPT files are loaded.