This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [PATCH] Add working-set size and hotness information to fdo summary (issue6465057)
>
> So I definitely preffer 2 or 3 over 1. David has experience with 3. How well does
> it work for LIPO?
>
This (lack of locking, races) is not a new problem. There is no
synchronization in libgcov for profile update/merge at both thread and
process level. Thread level data races leads to inconsistent counters,
but can be mostly corrected under -fprofile-correction and smoothing.
There is also problem with false indirect call targets --- gcc has
mechanism to filter those out.
Process level synchronization problems can happen when two processes
(running the instrumented binary) exit at the same time. The
updated/merged counters from one process may be overwritten by another
process -- this is true for both counter data and summary data.
Solution 3) does not introduce any new problems.
thanks,
David
> Honza
>>
>> Thanks,
>> Teresa
>>
>> >
>> > Honza
>>
>>
>>
>>
>> --
>> Teresa Johnson | Software Engineer | tejohnson@google.com | 408-460-2413