Implemented "no heap access" mode for JSFrame which is used for stack sampling in profiler.

Implemented "no heap access" mode for JSFrame which is used for stack sampling in profiler.

As I discovered that JSFrame accesses SharedFunctionInfo only to calculate caller SP and the latter is not used in profiler's stack sampling, I disabled accessing heap objects in JSFrame when doing stack sampling. This finally made V8's profiling stable when used from Chrome on a real web app.

Committed: http://code.google.com/p/v8/source/detail?r=1694

[Mikhail Naganov, 2009-04-13 22:48:21]

+sgjesse

[Søren Thygesen Gjesse, 2009-04-13 23:00:15]

LGTM

http://codereview.chromium.org/73020/diff/1/6
File src/frames.h (right):

http://codereview.chromium.org/73020/diff/1/6#newcode425
Line 425: void EnableNoHeapAccessMode() { no_heap_access_ = true; }
How about calling this DisableHeapAccess and the member variable
disable_heap_access_?

[Mikhail Naganov, 2009-04-13 23:10:26]

http://codereview.chromium.org/73020/diff/1/6
File src/frames.h (right):

http://codereview.chromium.org/73020/diff/1/6#newcode425
Line 425: void EnableNoHeapAccessMode() { no_heap_access_ = true; }
On 2009/04/13 23:00:15, Søren Gjesse wrote:
> How about calling this DisableHeapAccess and the member variable
> disable_heap_access_?

Done.

[iposva, 2009-04-13 23:16:08]

Small comment to be addressed in a new change list may be. Otherwise LGTM.

-Ivan

http://codereview.chromium.org/73020/diff/8/13
File src/frames.h (right):

http://codereview.chromium.org/73020/diff/8/13#newcode422
Line 422: // A shortcoming is that caller's SP value will be calculated
incorrectly
Is there a way where you can ASSERT if the caller's SP is accessed in this mode?