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

[Rong Xu via llvm-commits]

https://reviews.llvm.org/D82123

On Thu, Jun 18, 2020 at 11:39 AM Wei Mi <wmi at google.com> wrote:

> Ok, I will try it out using the multithreaded benchmark as well.
>
> On Thu, Jun 18, 2020 at 11:27 AM Rong Xu <xur at google.com> wrote:
>
>> BTW, I used google internal benchmarks that are highly threaded.  I don't
>> remember the exact numbers. But should be more than 10% runtime increase.
>>
>> On Thu, Jun 18, 2020 at 11:17 AM Rong Xu <xur at google.com> wrote:
>>
>>> 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
>>>>>>
>>>>>>
>>>>>>
>>>>>>
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