From: Jan Hubicka <hubicka@ucw.cz>
To: Xinliang David Li <davidxl@google.com>
Cc: "gcc@gcc.gnu.org" <gcc@gcc.gnu.org>,
Eugene Rozenfeld <Eugene.Rozenfeld@microsoft.com>
Subject: Re: State of AutoFDO in GCC
Date: Fri, 23 Apr 2021 21:28:34 +0200 [thread overview]
Message-ID: <20210423192834.GA1949@kam.mff.cuni.cz> (raw)
In-Reply-To: <CAAkRFZJObSNo3wSmhfHE0unYNKR5UDWv1D8GC0w0WkWwJo1GkA@mail.gmail.com>
> On Fri, Apr 23, 2021 at 10:27 AM Xinliang David Li <davidxl@google.com>
> wrote:
>
> >
> >
> > On Fri, Apr 23, 2021 at 10:16 AM Jan Hubicka <hubicka@ucw.cz> wrote:
> >
> >> >
> >> > It uses create_llvm_prof tool which is in the same git repo. The data
> >> > parsing part is shared with create_gcov, but the writer is obviously
> >> > different for the two tools.
> >>
> >> OK and what are the main differences between llvmand gcc format?
> >>
> >> GCC expects GCOV format, I think while LLVM uses a newly designed binary
> > format.
> >
> >
> Sorry I missed your next reply. I forgot about the details of GCC' format.
Thanks for explanation. How hard would be to make GCC consume this
format? Is is reasonably stable and documented somewhere?
Does LLVM's auto-FDO support non-Intel CPUs these days?
Honza
>
> David
> >
> >
> >> Honza
> >> >
> >> > David
> >> >
> >> >
> >> > > Honza
> >> > > >
> >> > > > David
> >> > > >
> >> > > > >
> >> > > > > Thoughts?
> >> > > > > Martin
> >> > > > >
> >> > > > > >
> >> > > > > > Having the tool third-party makes keeping the whole chain
> >> working
> >> > > more
> >> > > > > > difficult.
> >> > > > > >
> >> > > > > > Richard.
> >> > > > > >
> >> > > > > >> Thanks,
> >> > > > > >>
> >> > > > > >> David
> >> > > > > >>
> >> > > > > >> On Thu, Apr 22, 2021 at 3:29 PM Jan Hubicka <hubicka@ucw.cz>
> >> wrote:
> >> > > > > >>
> >> > > > > >>>> On 4/22/21 9:58 PM, Eugene Rozenfeld via Gcc wrote:
> >> > > > > >>>>> GCC documentation for AutoFDO points to create_gcov tool
> >> that
> >> > > > > converts
> >> > > > > >>> perf.data file into gcov format that can be consumed by gcc
> >> with
> >> > > > > >>> -fauto-profile (
> >> > > > > https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html,
> >> > > > > >>> https://gcc.gnu.org/wiki/AutoFDO/Tutorial).
> >> > > > > >>>>>
> >> > > > > >>>>> I noticed that the source code for create_gcov has been
> >> deleted
> >> > > from
> >> > > > > >>> https://github.com/google/autofdo on April 7. I asked about
> >> that
> >> > > > > change
> >> > > > > >>> in that repo and got the following reply:
> >> > > > > >>>>>
> >> > > > > >>>>>
> >> > > https://github.com/google/autofdo/pull/107#issuecomment-819108738
> >> > > > > >>>>>
> >> > > > > >>>>> "Actually we didn't use create_gcov and havn't updated
> >> > > create_gcov
> >> > > > > for
> >> > > > > >>> years, and we also didn't have enough tests to guarantee it
> >> works
> >> > > (It
> >> > > > > was
> >> > > > > >>> gcc-4.8 when we used and verified create_gcov). If you need
> >> it, it
> >> > > is
> >> > > > > >>> welcomed to update create_gcov and add it to the respository."
> >> > > > > >>>>>
> >> > > > > >>>>> Does this mean that AutoFDO is currently dead in gcc?
> >> > > > > >>>>
> >> > > > > >>>> Hello.
> >> > > > > >>>>
> >> > > > > >>>> Yes. I know that even basic test cases have been broken for
> >> years
> >> > > in
> >> > > > > the
> >> > > > > >>> GCC.
> >> > > > > >>>> It's new to me that create_gcov was removed.
> >> > > > > >>>>
> >> > > > > >>>> I tend to send patch to GCC that will remove AutoFDO from
> >> GCC.
> >> > > > > >>>> I known Bin spent some time working on AutoFDO, has he came
> >> up to
> >> > > > > >>> something?
> >> > > > > >>>
> >> > > > > >>> The GCC side of auto-FDO is not that hard. We have most of
> >> > > > > >>> infrastructure in place, but stopping point for me was always
> >> > > > > difficulty
> >> > > > > >>> to get gcov-tool working. If some maintainer steps up, I
> >> think I
> >> > > can
> >> > > > > >>> fix GCC side.
> >> > > > > >>>
> >> > > > > >>> I am bit unsure how important feature it is - we have FDO that
> >> > > works
> >> > > > > >>> quite well for most users but I know there are some users of
> >> the
> >> > > LLVM
> >> > > > > >>> implementation and there is potential to tie this with other
> >> > > hardware
> >> > > > > >>> events to asist i.e. if conversion (where one wants to know
> >> how
> >> > > well
> >> > > > > CPU
> >> > > > > >>> predicts the jump rather than just the jump probability)
> >> which I
> >> > > always
> >> > > > > >>> found potentially interesting.
> >> > > > > >>>
> >> > > > > >>> Honza
> >> > > > > >>>>
> >> > > > > >>>> Martin
> >> > > > > >>>>
> >> > > > > >>>>>
> >> > > > > >>>>> Thanks,
> >> > > > > >>>>>
> >> > > > > >>>>> Eugene
> >> > > > > >>>>>
> >> > > > > >>>>
> >> > > > > >>>
> >> > > > >
> >> > > > >
> >> > >
> >>
> >
next prev parent reply other threads:[~2021-04-23 19:28 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-22 19:58 Eugene Rozenfeld
2021-04-22 20:16 ` Martin Liška
2021-04-22 22:29 ` Jan Hubicka
2021-04-23 4:14 ` Xinliang David Li
2021-04-23 7:00 ` Richard Biener
2021-04-23 7:18 ` Martin Liška
2021-04-23 9:32 ` Richard Biener
2021-04-23 16:41 ` Xinliang David Li
2021-04-23 16:54 ` Jan Hubicka
2021-04-23 17:04 ` Xinliang David Li
2021-04-23 17:16 ` Jan Hubicka
2021-04-23 17:27 ` Xinliang David Li
2021-04-23 17:28 ` Xinliang David Li
2021-04-23 19:28 ` Jan Hubicka [this message]
2021-04-23 19:58 ` Xinliang David Li
2021-04-25 19:07 ` Jan Hubicka
2021-04-25 23:18 ` Xinliang David Li
2021-04-26 4:22 ` Wei Mi
2021-04-26 15:11 ` Andi Kleen
2021-04-26 16:57 ` Xinliang David Li
2021-04-26 18:00 ` Andi Kleen
2021-04-26 18:05 ` Xinliang David Li
2021-04-26 18:40 ` Hongtao Yu
2021-04-26 19:13 ` Andi Kleen
2021-04-29 5:40 ` Andi Kleen
2021-04-29 14:45 ` 172060045
2021-04-30 21:43 ` Andi Kleen
2021-05-08 11:25 ` 172060045
2021-05-09 16:28 ` Andi Kleen
2021-05-09 17:01 ` Jan Hubicka
2021-05-10 15:36 ` Andi Kleen
2021-05-10 16:55 ` Joseph Myers
2021-05-10 17:21 ` Andi Kleen
2022-07-26 20:12 ` Eugene Rozenfeld
2022-07-26 22:37 ` David Edelsohn
2022-07-27 7:26 ` Jan Hubicka
2022-07-27 18:30 ` [EXTERNAL] " Eugene Rozenfeld
2022-07-27 18:24 ` Eugene Rozenfeld
2022-07-27 1:31 ` Xionghu Luo
2022-07-27 1:41 ` Xionghu Luo
2022-07-27 18:38 ` [EXTERNAL] " Eugene Rozenfeld
2021-05-10 23:46 ` Wei Mi
2021-05-22 1:28 ` [EXTERNAL] " Eugene Rozenfeld
2021-05-22 16:36 ` Wei Mi
2021-05-25 1:39 ` Eugene Rozenfeld
2021-05-25 3:11 ` Wei Mi
2021-05-25 3:33 ` Eugene Rozenfeld
2021-05-25 3:54 ` Wei Mi
2021-05-25 7:01 ` Eugene Rozenfeld
2021-05-25 16:16 ` Wei Mi
2021-05-25 20:49 ` Eugene Rozenfeld
2021-05-26 3:06 ` Wei Mi
2021-05-26 23:39 ` Eugene Rozenfeld
2021-05-27 2:51 ` Wei Mi
2021-06-12 1:14 ` Eugene Rozenfeld
2021-06-14 17:00 ` Wei Mi
2021-04-23 17:20 ` Jan Hubicka
2021-04-23 16:36 ` Xinliang David Li
2021-04-30 18:48 ` [EXTERNAL] " Eugene Rozenfeld
2021-04-30 21:45 ` Andi Kleen
2021-06-24 21:45 ` Eugene Rozenfeld
2021-04-23 1:46 ` Bin.Cheng
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