674579 - Mobile: consider manually separating hot startup libxul from the rest

Status: RESOLVED INVALID

(Developer Infrastructure :: Source Code Analysis, defect)

Description

[Benjamin Stover (:stechz)]

To reduce the number of I/O accesses during startup before XRE_main, we could separate the code needed for startup from the rest of libxul.so. Taras estimates that we use about 20% of our binary code during startup, so this could cut reading and relocating down to a fraction of its current time.

Perhaps we could even speculatively load the other library after startup in a background thread?

PGO has the potential to do this work as well, but on Android we would probably need a custom version of GCC to move forward this way. To me this looks like a lot of work.

Comment 1

[(dormant account)]

(In reply to comment #0)
> PGO has the potential to do this work as well, but on Android we would
> probably need a custom version of GCC to move forward this way. To me this
> looks like a lot of work.

It really isn't. It's a few months of work.

Comment 2

[Mike Hommey [:glandium]]

(In reply to comment #0)
> Taras estimates that we use about 20% of our binary code during startup.

That's really more like 50%, IMO. And there are things that are hard to separate from each other.

Things I noted on the etherpad that could probably be separated out, with binary sizes:
- media libraries (vpx = 116k, ogg = 6k, nestegg = 12k, tremor = 67k, theora = 38k, sydneyaudio = 4k ; overall might not be worth the bother)
- svg (870k for libgkcontentsvg_s)
- webgl (buried in gfx, not sure it's big, but angle is 214k)
- uconv (714k, but we don't need all the converters until much later)
- necko (1M, that seems like a whole lot)
- (...)

Comment 3

[(dormant account)]

we need necko for startup.

Comment 4

[Mike Hommey [:glandium]]

(In reply to comment #3)
> we need necko for startup.

we certainly don't need most of it.

Comment 5

[Alon Zakai (:azakai)]

Is this bug covered by bug 632954 (PGO for android)?

Comment 6

[(dormant account)]

(In reply to Alon Zakai (:azakai) from comment #5)
> Is this bug covered by bug 632954 (PGO for android)?

It is not. In theory bug 686805 will make make this bug redundant

Comment 7

[Alon Zakai (:azakai)]

Ok, thanks for the info.