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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6A86CC433F5 for ; Tue, 9 Nov 2021 22:16:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 50FA76121F for ; Tue, 9 Nov 2021 22:16:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245329AbhKIWSo (ORCPT ); Tue, 9 Nov 2021 17:18:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50180 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245308AbhKIWSj (ORCPT ); Tue, 9 Nov 2021 17:18:39 -0500 Received: from mail-lf1-x12d.google.com (mail-lf1-x12d.google.com [IPv6:2a00:1450:4864:20::12d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 55918C061766 for ; Tue, 9 Nov 2021 14:15:52 -0800 (PST) Received: by mail-lf1-x12d.google.com with SMTP id k37so1058876lfv.3 for ; Tue, 09 Nov 2021 14:15:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=7QrN9bRgfv2t7Ph3CeDiEMr3mZQD8UAofqUlj1HpOcs=; b=GkgAIfu9ezIFiK4KZ+5DoTWP+7OhaAnP7ElKiVO2Z/tnmdBdyoXRmmmYTdh4yiHDqR FJ6aGaA2iwDDH6sL+8px318aC422k79jGfTn3n4PYhFiAP+oAr/1Kxy8MeW/VcDFh4NW /Q//TxdB9X7Ph0xtkVBJF2vLL8i7AdpiwCkE9pt3eVjNCKEIFCk7dcDYTMLwj7OeUe8w cIaA6IKl8OxrlAXoWD7ZQ/Zr9kgtAV6VVqEdm1dle4gya5wpvRv/To2QVunetDSQVxac ezVtKn1IeW0CGzq16WeLa7xaw3mlFJlNjBhQKO27nFafielOOp/PvY5LK7DXLQo99T6S IxCQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=7QrN9bRgfv2t7Ph3CeDiEMr3mZQD8UAofqUlj1HpOcs=; b=fDj682z+9qHGtS2MW8LLAN7p4DGEDNJPh/uKUXjnYVXtqPpUj5WaGhBosO5Xi2pZqU LecV8BOpPtK49AFruM9T+dPFEc7doMSVM6oQEe/y+Oo6qugxUbwebIJMGw6vY9RTdZuz WATeA4o5jwFmRo8dDkM3hSzwuZtFWsi8BRss5g+iTr2yyt7YfJImVYuqz+pRAkHgKu6j n1Pawae5iJ5SHl+fhBU+fQfplN2QlyDIPWUjT+Gwr0Vu1vsBSIgwjmmmqrpI3zhberLH lSEk57q1SGkafkgs3YzY1Q6317lwJgx1uqFDJAlRQpZFBD87joxiZD9WpewRErMNbWwn AT3Q== X-Gm-Message-State: AOAM530ISUxb1ezmb2GEINBHF1yJkoJO0hkQpJhskfl45NlcQQlIedaN PIMZRpsLmMrIpdBtxTFF3SLAfM1FXdheay+FsF/Mqw== X-Google-Smtp-Source: ABdhPJyh9ZFIMBC81wDRKs3l76rwu0iRTc8risc0IesJYz4dhXsjV5yYquNPiHQZ+xkcm63yiBOZm34LDtXc6OPtlGI= X-Received: by 2002:a05:6512:3d16:: with SMTP id d22mr613329lfv.523.1636496150443; Tue, 09 Nov 2021 14:15:50 -0800 (PST) MIME-Version: 1.0 References: <20211105171023.989862879@infradead.org> <20211105171821.654356149@infradead.org> <20211108164711.mr2cqdcvedin2lvx@treble> <20211109212116.GW174703@worktop.programming.kicks-ass.net> <20211109221130.GA174703@worktop.programming.kicks-ass.net> In-Reply-To: <20211109221130.GA174703@worktop.programming.kicks-ass.net> From: Nick Desaulniers Date: Tue, 9 Nov 2021 14:15:38 -0800 Message-ID: Subject: Re: [PATCH 20/22] x86,word-at-a-time: Remove .fixup usage To: Peter Zijlstra , Bill Wendling Cc: Josh Poimboeuf , x86@kernel.org, linux-kernel@vger.kernel.org, mark.rutland@arm.com, dvyukov@google.com, seanjc@google.com, pbonzini@redhat.com, mbenes@suse.cz, llvm@lists.linux.dev, linux-toolchains@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 9, 2021 at 2:11 PM Peter Zijlstra wrote: > > On Tue, Nov 09, 2021 at 01:25:47PM -0800, Nick Desaulniers wrote: > > On Tue, Nov 9, 2021 at 1:21 PM Peter Zijlstra wrote: > > > > > > On Tue, Nov 09, 2021 at 12:59:12PM -0800, Bill Wendling wrote: > > > > > > > > Adding attributes to labels shouldn't be difficult, as you mention. In > > > > the case of cold/hot, it's adjusting some of the metadata that already > > > > exists on some basic blocks. It might be enough to allow the normal > > > > block placement algorithms to move the hot and cold blocks around for > > > > us. The question becomes how many attributes does GCC allow on labels? > > > > > > I'm aware of 3: unused, hot, cold. Also: > > > > > > https://gcc.gnu.org/onlinedocs/gcc/Label-Attributes.html > > > > Re: unused: > > Being able to selectively disable -Wunused-label via > > __attribute__((unused)); seems useful, too. > > kernel/sched/fair.c:done: __maybe_unused; > > Yes it is ;-) Ah, that's already supported: https://godbolt.org/z/aa76aexnv, so it's just hot/cold that could be implemented next. -- Thanks, ~Nick Desaulniers