From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from nikam.ms.mff.cuni.cz (nikam.ms.mff.cuni.cz [195.113.20.16]) by sourceware.org (Postfix) with ESMTPS id EDF103857C44 for ; Sun, 25 Apr 2021 19:07:56 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org EDF103857C44 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=ucw.cz Authentication-Results: sourceware.org; spf=none smtp.mailfrom=hubicka@kam.mff.cuni.cz Received: by nikam.ms.mff.cuni.cz (Postfix, from userid 16202) id F1AB2282C12; Sun, 25 Apr 2021 21:07:54 +0200 (CEST) Date: Sun, 25 Apr 2021 21:07:54 +0200 From: Jan Hubicka To: Xinliang David Li Cc: "gcc@gcc.gnu.org" , Eugene Rozenfeld , Wei Mi Subject: Re: State of AutoFDO in GCC Message-ID: <20210425190754.GA88857@kam.mff.cuni.cz> References: <20210423165449.GC56452@kam.mff.cuni.cz> <20210423171611.GA82007@kam.mff.cuni.cz> <20210423192834.GA1949@kam.mff.cuni.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Spam-Status: No, score=-8.2 required=5.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, KAM_DMARC_STATUS, KAM_LAZY_DOMAIN_SECURITY, KAM_SHORT, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=no autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: gcc@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 25 Apr 2021 19:07:59 -0000 David, > > The text format is documented here: > https://clang.llvm.org/docs/UsersManual.html > The binary format is not documented. The binary format is not guaranteed to > be backward compatible, so sharing the same format may not be the best way > as changes for clang may break GCC. > > Since linux perf format does not change, the tool should be relatively > stable with low maintenance cost. Changes are needed only when some new > AutoFDO features are added to the compiler side. I was under impression that it is indeed problem with the tool requiring old format of linux perf. At least with opensuse distro the shipped tool fails for me: jan@skylake:~> create_llvm_prof --binary=./code --out=code.prof E0425 21:01:55.038128 17977 perf_reader.cc:996] Unsupported event type 79 F0425 21:01:55.038295 17977 perf_parser.cc:240] Check failed: reader_.ReadPerfSampleInfo(*parsed_event.raw_event, &sample_info) *** Check failure stack trace: *** @ 0x55e6deb6058e (unknown) @ 0x55e6deb94a49 (unknown) .. Aborted (core dumped) I collect data as intstructed here: https://clang.llvm.org/docs/UsersManual.html It is from package autofdo-0.18-4.4.x86_64 and perf 5.11.15. Is there a way to get this working w/o using older perf? Honza > > Does LLVM's auto-FDO support non-Intel CPUs these days? > > > > It supports LBR like events, so it is CPU vendor dependent. For ARM, using > ETM can achieve the goal, but I don't have detailed knowledge of it. > > David > > > > > 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 > > > >> > > > > >>>>> > > > >> > > > > >>>> > > > >> > > > > >>> > > > >> > > > > > > > >> > > > > > > > >> > > > > > >> > > > > > >