From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A233B2AD00; Sun, 11 Oct 2026 20:10:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791749441; cv=none; b=ORjQhmN/MHb/9g1PuTHB+hCaxItwlvOqot8x93u9B7xXfAfvCXZoeP1MoCRi6LC6Ae7LB8aLpDifaykNeNN/mhcTX0s+9EdHqH2MIlWe03FBgK+mC3SzVVCpl1JzeOxQgPiEMLer4SniVEae/swVkypj72HPvig90+ABFsA9RRE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791749441; c=relaxed/simple; bh=0lW7NXlLWcW3JHmAsxnYfuMkROJlPGhMtERY68ouGdY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=FKLJxEe28TcoU3fpl5T2ApGYlDqytHBl8KibColGlHfijtlqaLRZfFzYGOhlWEdnfxHDP2AywnXwmX6Cj7eersBdSELuwGWDmwe84BUhRtTpgOle2Dm0JEHuu3f8LHlRw7DbRjcuCGKdruelXkuYc888LAexYjNxicfRdMSqUcU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=PFEG18UE; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="PFEG18UE" Received: from [IPV6:2601:646:8003:f231:99ff:bd5:ac70:6da0] ([IPv6:2601:646:8003:f231:99ff:bd5:ac70:6da0]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 69BK83d82753795 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Sun, 11 Oct 2026 13:08:04 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 69BK83d82753795 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2026092801; t=1791749287; bh=38kwe/MM4HFYzJyg54GfyoGLCPo81FIpxmyL9rCu+jU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=PFEG18UEjBlsJ1Kx+OxwBMu4T1HzMqDczww7DDQYUMOjd4B+hI6krRm5lZJAUOFWA U6G+DKWwJx2GI6jNoTsSgBKTdm6G+YSIZAamT1i/qJnCVKfbcgSKCarMGGm00SIbR7 ra7QFi0GrMJMU5/1zw2at3uJ6a7sE5FkQkkJQbzn/uJxhbg4jjRaLikmXiSNwGM4mT wLp/O73yY0PsviG8OH5mV1uk0H6UrBVEuf3Khr5U66PceZ0eGvA41fbS+MxmCQIrdv QuAKyzpy051ZzZeVqZPho8kJ3TfSBinSckjQ6t5eBHu0vUFFljMJI1AojWyVRLAhJm H6P3IkA5oFDWA== Message-ID: <1d34d990-fe55-4bb7-99b9-82ca201a031d@zytor.com> Date: Sun, 11 Oct 2026 13:07:58 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 2/2] x86: Start removing X86_X32_ABI To: Willy Tarreau , Sebastian Andrzej Siewior Cc: Tancred , Sebastian Andrzej Siewior , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, "Maciej W. Rozycki" , Bill Wendling , Borislav Petkov , Dave Hansen , Ingo Molnar , John Paul Adrian Glaubitz , Jonathan Corbet , Justin Stitt , Nathan Chancellor , Neal Gompa , Nick Desaulniers , Richard Purdie , Sam James , Shuah Khan , Thomas Gleixner , =?UTF-8?Q?Thomas_Wei=C3=9Fschuh?= , Tomas Glozar , x86@kernel.org, Arnd Bergmann References: <20261008-x32_removal-v4-0-d389a193c506@breakpoint.cc> <20261008-x32_removal-v4-2-d389a193c506@breakpoint.cc> <7f315c7a-0fd1-4f7e-93bb-703d4107aa5a@narraduct.com> <20261011171946.gMv8V9Ck@breakpoint.cc> Content-Language: en-US, sv-SE From: "H. Peter Anvin" In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2026-10-11 10:38, Willy Tarreau wrote: > On Sun, Oct 11, 2026 at 07:19:46PM +0200, Sebastian Andrzej Siewior wrote: >> On 2026-10-09 20:13:55 [-0600], Tancred wrote: >>> >>> >>> On 10/8/26 03:07, Sebastian Andrzej Siewior wrote: >>>> where certain workloads widely >>>> move to x32 and use it exclusively. In the meantime Debian introduced a >>>> patch to disable x32 by default (so it has to be enabled at boot time on >>>> the command line) because they are afraid of the increased attack >>>> surface. Fedora as far as I tell has X32 disabled (looking at 7.0-rc5 >>>> rpm in rawhide). >>>> >>>> Since there is practically no real use for x32 >>> >>> I only recently discovered x32 and built a Desktop (with all daemons and >>> utilities running 10-30% smaller and some a bit faster, with 64 bit >>> libraries for eg. Firefox.) My experiment should definitely not decide >>> anything, but how much real-world use would be sufficient to justify >>> continued presence (more complex compat code)? >> >> "a bit faster" needs actual numbers to justify. One examples was quicker >> gcc but I don't see a x32 compile farm leveraging this benefit. > > FWIW I do build my ARM cross-compilers in a32 because they're generally > ~10-15% faster than in a64. I wouldn't be surprised if that was the same > on x86 because tools such as compilers very likely use pointers a lot. In > a build farm it certainly makes a difference, possibly not sufficient to > justify keeping a kernel port, but it's just to illustrate one valid use > case. > Compilers is known to be significantly faster with x32, because compilers use a *lot* of pointers. However, even compilers are starting to need > 4 GiB of memory in many configurations, especially when using LTO. -hpa