[PATCH] RFC: Cache LTO streamer mappings

Jan Hubicka hubicka@ucw.cz
Wed Oct 12 12:31:00 GMT 2011

> On Sun, Oct 9, 2011 at 13:11, Andi Kleen <andi@firstfloor.org> wrote:
> > Is it still a good idea?
> Given that you found no speedups and it introduces added complexity, I
> think it's best if we revisit the idea later.  I never found bytecode
> reading to be a bottleneck in LTO, but perhaps Jan can comment what
> the experience is with Mozilla builds.

WPA is currently about 1/3 of reading&type merging, 1/3 of streaming out and
1/3 of inlining.  inlining is relatively easy to cure, so yes, streaming
performance is important.  The very basic streaming primitives actualy still
shows top in profile along with hashing and type comparing code.  I will post
some updated oprofiles into Mozilla PR.

Honestly I think we won't get any great speedups unless we work on reducing amount of
unnecesary info we pickle/unpickle.

> Diego.

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