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,URIBL_BLOCKED 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 C8E16C07E95 for ; Fri, 2 Jul 2021 18:58:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD1E36141C for ; Fri, 2 Jul 2021 18:58:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230243AbhGBTA5 (ORCPT ); Fri, 2 Jul 2021 15:00:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44464 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229536AbhGBTA5 (ORCPT ); Fri, 2 Jul 2021 15:00:57 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B0337C061762 for ; Fri, 2 Jul 2021 11:58:24 -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=OOFkg3bgn9LW9+M4UE4UvleU2R47+ykAYhZOcWI/BnM=; b=TSGGYBoFIVnvrAjOFhmYiZ3q1w Sf/gG2mSYgDuJr21duKFO/pFqyM3zwH9rpDy4zGx7JkMugbh/SghVHX0rjSTGRIFIro7/7qMSjrmb XsAp1GQG1X6Ugqu8R+r+GUWeU8qnaEa+R7GXn0mV1kV7AdarV8NMCh1NArBn0EBJUihpUFrY3KalT knmfkdpV8ts/6+HSfxR4oOaEuf4ubXqsz114c5SFBv/ff/IyVv9Q1oqQVmbmUdwjunnw89C+q7mRm 8ntAKm/7HZ7OJ78vKkAJTwpSZDCQ0K98i+Swrp31J+3LfxqaB0Mh3ILGdDo4uKYj69TDrkUdZk9AQ zegaKM5g==; 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 #2 (Red Hat Linux)) id 1lzOM8-007y5D-Qg; Fri, 02 Jul 2021 18:57:44 +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 4542E300091; Fri, 2 Jul 2021 20:57:39 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 245882B8556D4; Fri, 2 Jul 2021 20:57:39 +0200 (CEST) Date: Fri, 2 Jul 2021 20:57:39 +0200 From: Peter Zijlstra To: Nick Desaulniers Cc: Bill Wendling , Linus Torvalds , Kees Cook , Linux Kernel Mailing List , Bill Wendling , Catalin Marinas , clang-built-linux , Fangrui Song , Heiko Carstens , Jarmo Tiitto , Lukas Bulwahn , Mark Rutland , Masahiro Yamada , Miguel Ojeda , Nathan Chancellor , Peter Oberparleiter , Sami Tolvanen , Will Deacon Subject: Re: [GIT PULL] Clang feature updates for v5.14-rc1 Message-ID: References: <202106281231.E99B92BB13@keescook> <202106291311.20AB10D04@keescook> 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 Fri, Jul 02, 2021 at 10:26:40AM -0700, Nick Desaulniers wrote: > On Fri, Jul 2, 2021 at 5:57 AM Peter Zijlstra wrote: > > I've asked this before; *what* is missing from LBR samples that's > > reponsible for the performance gap? > > Are we able to collect LBR samples from __init code? I can imagine > trying to launch perf from init/pid 1, but I suspect at that point > it's way too late. > > Increasingly, boot times of hosts (and virtualized guests) are > becoming important to us, both in the datacenters and on mobile. For a guest, possibly, I've no idea how any of that virt crud works.