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 45206388A400 for ; Fri, 23 Apr 2021 17:16:12 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 45206388A400 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 10E62282612; Fri, 23 Apr 2021 19:16:11 +0200 (CEST) Date: Fri, 23 Apr 2021 19:16:11 +0200 From: Jan Hubicka To: Xinliang David Li Cc: "gcc@gcc.gnu.org" , Eugene Rozenfeld Subject: Re: State of AutoFDO in GCC Message-ID: <20210423171611.GA82007@kam.mff.cuni.cz> References: <62330f82-201d-af7d-d1ed-1c8c529cc0f7@suse.cz> <20210422222906.GB5803@kam.mff.cuni.cz> <20210423165449.GC56452@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: Fri, 23 Apr 2021 17:16:14 -0000 > > 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? 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 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 > > > > >>>>> > > > > >>>> > > > > >>> > > > > > > > > > >