From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EC031C48BE8 for ; Mon, 14 Jun 2021 07:52:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D3CC661352 for ; Mon, 14 Jun 2021 07:52:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232634AbhFNHyR (ORCPT ); Mon, 14 Jun 2021 03:54:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53330 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232530AbhFNHyP (ORCPT ); Mon, 14 Jun 2021 03:54:15 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2F230C061574; Mon, 14 Jun 2021 00:52:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=tgENEbQ1euA5WeQRBjJGfSzObO0naqGm4XxibhoeuXo=; b=iMpjx/GXaZ+XhmNRXa/ado21wl wD5TGdYlVLzw3tvlr/zeUSKT/XqtKhdFuV5pIOpOreJNHCPO5XCwX8Zyi0sV+2mwMqxlWSvd3QrC2 RxISmfX/SZT5lkTE6Alpr9G6NjY406Ob3XQJgT2Xh9uj6TB9v7AqS7aRNHlwHn+SxI1a3dmi9WusU qokkqIl63NVzkunlle3IHsWhpSYOSNvkFB6xeoBjKdct6KCGLrR2Ne7A+k6wzyL1kS7AEx/owvG4+ 0CqQsWhXTJfjVPY22Z075b4Y2If9w9vvgYKQt4A6fqr+H6Mx84Gqdq3kMHICfRFLA8KOl4unWjtDD 7SamNObQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94 #2 (Red Hat Linux)) id 1lshNd-0058rV-UV; Mon, 14 Jun 2021 07:51:49 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 00B8B300252; Mon, 14 Jun 2021 09:51:31 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id DA0252026A646; Mon, 14 Jun 2021 09:51:31 +0200 (CEST) Date: Mon, 14 Jun 2021 09:51:31 +0200 From: Peter Zijlstra To: Bill Wendling Cc: Kees Cook , Jonathan Corbet , Masahiro Yamada , Linux Doc Mailing List , LKML , Linux Kbuild mailing list , clang-built-linux , Andrew Morton , Nathan Chancellor , Nick Desaulniers , Sami Tolvanen , Fangrui Song , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" Subject: Re: [PATCH v9] pgo: add clang's Profile Guided Optimization infrastructure Message-ID: References: <20210111081821.3041587-1-morbo@google.com> <20210407211704.367039-1-morbo@google.com> <20210612202505.GG68208@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jun 12, 2021 at 01:56:41PM -0700, Bill Wendling wrote: > For example, Fangrui gave you numbers, and you rejected them out of > hand. I've explained to you why instrumentation is better than > sampling (at least for clang). Fangrui gave you numbers. Let's move on > to something else. I did not dismiss them; I asked for clarification. I would like to understand what exactly is missed by sampling based PGO data that makes such a difference.