Fix crbug/24815. Changes affect profiler "lazy" mode used for V8 in Chromium.

Fix crbug/24815. Changes affect profiler "lazy" mode used for V8 in Chromium.

- don't engage the processing thread of CPU profiling until the first time profiling is resumed, this saves us a thread allocation for the majority of users;
- don't log shared libraries addresses: this is useless for JS-only profiling, and also consumes time on startup.

Committed: http://code.google.com/p/v8/source/detail?r=3154

[Søren Thygesen Gjesse, 2009-10-28 08:51:10]

LGTM for solving http://crbug.com/24815

However I think the naming and effects of flags prof/prof_auto/prof_lazy should
be revised. Maybe some of this configuration can be moved to the API.

http://codereview.chromium.org/340013/diff/1/2
File src/log.cc (right):

http://codereview.chromium.org/340013/diff/1/2#newcode250
Line 250: : head_(0),
Four space indent for :.

http://codereview.chromium.org/340013/diff/1/2#newcode263
Line 263: if (!FLAG_prof_lazy) {
This is a bit subtle, as the use of prof_lazy (which should be renamed) does not
necessarily imply that JavaScript only profiling is intended.

[mnaganov (inactive), 2009-10-28 09:12:08]

Thanks, Søren! I agree with you that we need to simplify those flags. I've
created http://code.google.com/p/v8/issues/detail?id=487 to track this issue.

On 2009/10/28 08:51:10, Søren Gjesse wrote:
> LGTM for solving http://crbug.com/24815
> 
> However I think the naming and effects of flags prof/prof_auto/prof_lazy
should
> be revised. Maybe some of this configuration can be moved to the API.
> 
> http://codereview.chromium.org/340013/diff/1/2
> File src/log.cc (right):
> 
> http://codereview.chromium.org/340013/diff/1/2#newcode250
> Line 250: : head_(0),
> Four space indent for :.
> 
> http://codereview.chromium.org/340013/diff/1/2#newcode263
> Line 263: if (!FLAG_prof_lazy) {
> This is a bit subtle, as the use of prof_lazy (which should be renamed) does
not
> necessarily imply that JavaScript only profiling is intended.