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From: "qing.zhao at oracle dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug gcov-profile/95348] GCC records zero functions and modules in
 the profiling data file, ICC does NOT
Date: Wed, 10 Jun 2020 20:17:06 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95348

--- Comment #31 from Qing Zhao <qing.zhao at oracle dot com> ---
> The explanation is not sufficient.
You mean the following explanation: (in comment 18)

we tried the scheme that all the processes generate profiling feedback data=
 to
the single directory,=20
but looks like a lot of profiling info got lost, resulting bad performance
effect.=20
We thought this might relate to the parallel running environment of our
application,=20
then we switched to this current approach.=20

Per the documentation of -fprofile-dir=3Dpath at:
https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html
<https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html>

"When an executable is run in a massive parallel environment, it is recomme=
nded
to save profile to different folders.
 That can be done with variables in path that are exported during run-time:
%p
process ID.

%q{VAR}
value of environment variable VAR"


> You mentioned that merging takes 24 hours, so I would expect that directi=
ng
> merging will same you quite some time.
Yes, that will help.
But at the same time, if the profiling feedback size can be reduced, then t=
he
time for merging will be reduced too.=20

> I'm still missing information like:
> - how long does it take the training run?
I have asked the question too (I don=E2=80=99t have permission to run that =
real app, so
I need to collect such info from other engineer), but no answer so far.
> - how many parallel runs do you have?
Over 10000 processes are running at the same time.=20
> - what's the average duration of a process?
I have asked the question too, no answer so far.=