[PATCH] D81981: [PGO] Supplement PGO profile with Sample profile

[Rong Xu via llvm-commits]

Ok, got it . That's probably a single thread program. Instrumentation
overhead is low.

On Thu, Jun 18, 2020 at 11:13 AM Wei Mi <wmi at google.com> wrote:

>
>
> On Thu, Jun 18, 2020 at 10:49 AM Rong Xu <xur at google.com> wrote:
>
>>
>>
>> On Wed, Jun 17, 2020 at 3:07 PM Wei Mi via Phabricator <
>> reviews at reviews.llvm.org> wrote:
>>
>>> wmi added a comment.
>>>
>>> In D81981#2099070 <https://reviews.llvm.org/D81981#2099070>, @davidxl
>>> wrote:
>>>
>>> > I think it is good to have an entry counter always, so that the
>>> profile dump is more readable. Do you have data showing the instrumentation
>>> overhead and profile size impact (clang and some large app)?
>>>
>>>
>>> Yes, I tried clang. The instrumentation runtime overhead increases by
>>> about 0.8%. The raw profile size increases by 1.8%. The zipped profile size
>>> increases by 0.15%.
>>> Right now in the patch, inserting entry counter is guarded by a flag
>>> with default value being false.
>>>
>>> How did you test clang. This is for one file or for the whole clang?
>> To me, 0.8% is close to nothing.
>> My previous patch shows much more than this for a highly threaded
>> program.
>>
>
> This is to use clang to compile a single large file as a test.
>
>
>
>>
>>> Repository:
>>>   rL LLVM
>>>
>>> CHANGES SINCE LAST ACTION
>>>   https://reviews.llvm.org/D81981/new/
>>>
>>> https://reviews.llvm.org/D81981
>>>
>>>
>>>
>>>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20200618/ba2b2699/attachment.html>