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=-13.2 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 05F2DC4361B for ; Wed, 9 Dec 2020 16:12:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C1B0423B51 for ; Wed, 9 Dec 2020 16:12:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731360AbgLIQMJ (ORCPT ); Wed, 9 Dec 2020 11:12:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52260 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731095AbgLIQLz (ORCPT ); Wed, 9 Dec 2020 11:11:55 -0500 Received: from mail-ua1-x944.google.com (mail-ua1-x944.google.com [IPv6:2607:f8b0:4864:20::944]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A25BCC061793 for ; Wed, 9 Dec 2020 08:11:14 -0800 (PST) Received: by mail-ua1-x944.google.com with SMTP id 4so657740uap.8 for ; Wed, 09 Dec 2020 08:11:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=RAzf84xm2mgxYvHDSz3COzuojd6IcnSxMMVRpqKMx58=; b=gIACvSNIaNgfk8yYU6S+oPUv61DEJWlMah84jEakzPWNcyXSQgGfZRUQCmTA2z2H68 OBzeyFblbpXMDN4KMc97LtU39WqbsHFa8AfAomXUSKTieYHPNM7GEZ6ZC1XAJfkKWHDD N/rGmO7I1HBChFKlMvhDUHT+DD0u7soRUGjQ6XTsXx6XX9hNVWvtKbx0EmKVXSx0x63q uSx0K2QC6qZIjcT/Vy+GTkse17WcJ35wK97vuG6odXGIYTCqk24f8kQwlYGGa1smU8sB zozuG5IW1kXDMdiObqppDeT7967KYlhg+uX66AupNL004gGWmHXS7ElwVjsdgyVqwHeF qKYA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=RAzf84xm2mgxYvHDSz3COzuojd6IcnSxMMVRpqKMx58=; b=fAXnMALUhi8hxF24ZP0gvT7ikL6GyaIj0EGb3TQ29pT7efda4q8YR2N57kCr/nV+Xa Ri9MZH1jO2mWyUiXjxO7YYeHVYXt+cLWFlElEMJ6knenyRtGpxf+N2Wsw9KYAn38vrlS /0xKjnYYq6ApDpOVcxD//vwIzTflrCX+N0mOQkQJ/hw4mHgCCd26i+mTJXzGFzLjYS8A CPf19OOXTLBu1YOrUi5deZhpLESoaKzPgKk4YgJ2k58ZIUz8fc0pSTs62OJAFIOSi6bw hD8Xi7BNCQ4kPWYt2mbZDAtEMdhuLZ/oVIfIfnPTSWWxdu8Jia92ryI9rY/+irgxJIVw 3cxg== X-Gm-Message-State: AOAM530so+ifgvdgZqWFlM5BMIv/KohWR/qghkBXbWli8T6UOvK/i9gd 7uoQpe6gM3MvltQ29zcXR1Xv94WTDxrbwVvvJvq8Xg== X-Google-Smtp-Source: ABdhPJxCOtYM6wE6I23ECIs2Qe4RqO9Fsld+KWhukNaUvLqxacy6A4k/Hk6QX5PPXhxx/JBHh4wZPl2Wms4urz4X8pg= X-Received: by 2002:ab0:1c0a:: with SMTP id a10mr2343531uaj.89.1607530273519; Wed, 09 Dec 2020 08:11:13 -0800 (PST) MIME-Version: 1.0 References: <20201201213707.541432-1-samitolvanen@google.com> In-Reply-To: From: Sami Tolvanen Date: Wed, 9 Dec 2020 08:11:02 -0800 Message-ID: Subject: Re: [PATCH v8 00/16] Add support for Clang LTO To: Arnd Bergmann Cc: Nick Desaulniers , Masahiro Yamada , Steven Rostedt , Will Deacon , Josh Poimboeuf , Peter Zijlstra , Greg Kroah-Hartman , "Paul E. McKenney" , Kees Cook , clang-built-linux , Kernel Hardening , linux-arch , Linux ARM , Linux Kbuild mailing list , "linux-kernel@vger.kernel.org" , linux-pci Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 8, 2020 at 2:20 PM Arnd Bergmann wrote: > > On Tue, Dec 8, 2020 at 10:10 PM 'Nick Desaulniers' via Clang Built > Linux wrote: > > > > On Tue, Dec 8, 2020 at 1:00 PM Arnd Bergmann wrote: > > > > > > On Tue, Dec 8, 2020 at 5:43 PM 'Sami Tolvanen' via Clang Built Linux > > > wrote: > > > > > > > > On Tue, Dec 8, 2020 at 4:15 AM Arnd Bergmann wrote: > > > > > > > > > > - one build seems to take even longer to link. It's currently at 35GB RAM > > > > > usage and 40 minutes into the final link, but I'm worried it might > > > > > not complete > > > > > before it runs out of memory. I only have 128GB installed, and google-chrome > > > > > uses another 30GB of that, and I'm also doing some other builds in parallel. > > > > > Is there a minimum recommended amount of memory for doing LTO builds? > > > > > > > > When building arm64 defconfig, the maximum memory usage I measured > > > > with ThinLTO was 3.5 GB, and with full LTO 20.3 GB. I haven't measured > > > > larger configurations, but I believe LLD can easily consume 3-4x that > > > > much with full LTO allyesconfig. > > > > > > Ok, that's not too bad then. Is there actually a reason to still > > > support full-lto > > > in your series? As I understand it, full LTO was the initial approach and > > > used to work better, but thin LTO is actually what we want to use in the > > > long run. Perhaps dropping the full LTO option from your series now > > > that thin LTO works well enough and uses less resources would help > > > avoid some of the problems. > > > > While all developers agree that ThinLTO is a much more palatable > > experience than full LTO; our product teams prefer the excessive build > > time and memory high water mark (at build time) costs in exchange for > > slightly better performance than ThinLTO in > told are important>. Keeping support for full LTO in tree would help > > our product teams reduce the amount of out of tree code they have. As > > long as help > > sell/differentiate phones, I suspect our product teams will continue > > to ship full LTO in production. > > Ok, fair enough. How about marking FULL_LTO as 'depends on > !COMPILE_TEST' then? I'll do that locally for my randconfig tests, > but it would help the other build bots that also force-enable > COMPILE_TEST. Sure, that sounds reasonable to me. I'll add it in v9. Sami 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=-3.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_ADSP_CUSTOM_MED,DKIM_SIGNED,DKIM_VALID,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 0B9ECC4361B for ; Wed, 9 Dec 2020 16:12:31 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id BAB9123B51 for ; Wed, 9 Dec 2020 16:12:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BAB9123B51 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:To:Subject:Message-ID:Date:From:In-Reply-To: References:MIME-Version:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=I+NzQC3Sb8vvJej7aoxBw4S4gk/xm5ce9iLJTUzBFrM=; b=K9bmdM/+wJ37GGnruGXdUGpLF +gXnly8157BBaAsiL8Y+sSN+Vn2Uqg/tCepNw3fPZG/XlgtLK0vY0eJZPTkixV7PWF7YTlNwBHgi/ Nz3aPLu7GO64lztox118GXKCIc6ll2+8xyWMIFOuNcPLvb2h35R21qQJCveF99Zcqsz9SCS9NwzcO exF5JuUjnwW66zFIBr683k6keNhunC8lPxh1bmGA8sr1wn18ikkFZPhnGA+kAAUALYHkvOwj+gPYG +tYXdDHnRC4WAvy6JicBhuDbcPm+ujn8ZJLzepeRpTPgtHvpIgKFNU5s1Kd7heEQcxad8OX0tp+tx T+ZaAOtew==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kn23i-0005cC-Li; Wed, 09 Dec 2020 16:11:18 +0000 Received: from mail-ua1-x942.google.com ([2607:f8b0:4864:20::942]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kn23f-0005aj-Uq for linux-arm-kernel@lists.infradead.org; Wed, 09 Dec 2020 16:11:17 +0000 Received: by mail-ua1-x942.google.com with SMTP id p2so660694uac.3 for ; Wed, 09 Dec 2020 08:11:15 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=RAzf84xm2mgxYvHDSz3COzuojd6IcnSxMMVRpqKMx58=; b=gIACvSNIaNgfk8yYU6S+oPUv61DEJWlMah84jEakzPWNcyXSQgGfZRUQCmTA2z2H68 OBzeyFblbpXMDN4KMc97LtU39WqbsHFa8AfAomXUSKTieYHPNM7GEZ6ZC1XAJfkKWHDD N/rGmO7I1HBChFKlMvhDUHT+DD0u7soRUGjQ6XTsXx6XX9hNVWvtKbx0EmKVXSx0x63q uSx0K2QC6qZIjcT/Vy+GTkse17WcJ35wK97vuG6odXGIYTCqk24f8kQwlYGGa1smU8sB zozuG5IW1kXDMdiObqppDeT7967KYlhg+uX66AupNL004gGWmHXS7ElwVjsdgyVqwHeF qKYA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=RAzf84xm2mgxYvHDSz3COzuojd6IcnSxMMVRpqKMx58=; b=acBLeXznh3Mp/VfEUmC0SLA0PLWVri2i7xe3uyl8E6igitqk/UYfr25TN+0Vuyfc+J AtfWvZrEPvX3uon7V3D3pLqFEmMgTQt3BoPxz9NQeR5w1X31II57s6Q2MHrCc2vkdlma K3pvRD+ZYiaqPXTe72I9gPSRe9d+37M+0cX7fJIjHufWuHjGJKFqyj6XimCDDjbqcql3 wnQcxwTnZ8wvKo/CVPoCgukL3YdhjbhWrK2y8oDsh/Buqmb7p0kMDCjFBLELaubgB+dP Ke1ctbHbbGPjhabUtA8nc11w6kvvF+8Qn6NHmkbFjyz6Mh3cjKmZTklKy6S7DvfN01f0 aaYg== X-Gm-Message-State: AOAM5300Clxz3eBkxYWEtK1myeWtR/RewqwTRiDsq4Gb1NyETRvcdnJ5 YbHKilqtagxZwptDYONYiE5lq7TNkrQ5LsKoY98Ubg== X-Google-Smtp-Source: ABdhPJxCOtYM6wE6I23ECIs2Qe4RqO9Fsld+KWhukNaUvLqxacy6A4k/Hk6QX5PPXhxx/JBHh4wZPl2Wms4urz4X8pg= X-Received: by 2002:ab0:1c0a:: with SMTP id a10mr2343531uaj.89.1607530273519; Wed, 09 Dec 2020 08:11:13 -0800 (PST) MIME-Version: 1.0 References: <20201201213707.541432-1-samitolvanen@google.com> In-Reply-To: From: Sami Tolvanen Date: Wed, 9 Dec 2020 08:11:02 -0800 Message-ID: Subject: Re: [PATCH v8 00/16] Add support for Clang LTO To: Arnd Bergmann X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201209_111116_080811_02B77F6C X-CRM114-Status: GOOD ( 26.49 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch , Kees Cook , "Paul E. McKenney" , Kernel Hardening , Peter Zijlstra , Greg Kroah-Hartman , Masahiro Yamada , Linux Kbuild mailing list , Nick Desaulniers , "linux-kernel@vger.kernel.org" , Steven Rostedt , clang-built-linux , linux-pci , Josh Poimboeuf , Will Deacon , Linux ARM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Dec 8, 2020 at 2:20 PM Arnd Bergmann wrote: > > On Tue, Dec 8, 2020 at 10:10 PM 'Nick Desaulniers' via Clang Built > Linux wrote: > > > > On Tue, Dec 8, 2020 at 1:00 PM Arnd Bergmann wrote: > > > > > > On Tue, Dec 8, 2020 at 5:43 PM 'Sami Tolvanen' via Clang Built Linux > > > wrote: > > > > > > > > On Tue, Dec 8, 2020 at 4:15 AM Arnd Bergmann wrote: > > > > > > > > > > - one build seems to take even longer to link. It's currently at 35GB RAM > > > > > usage and 40 minutes into the final link, but I'm worried it might > > > > > not complete > > > > > before it runs out of memory. I only have 128GB installed, and google-chrome > > > > > uses another 30GB of that, and I'm also doing some other builds in parallel. > > > > > Is there a minimum recommended amount of memory for doing LTO builds? > > > > > > > > When building arm64 defconfig, the maximum memory usage I measured > > > > with ThinLTO was 3.5 GB, and with full LTO 20.3 GB. I haven't measured > > > > larger configurations, but I believe LLD can easily consume 3-4x that > > > > much with full LTO allyesconfig. > > > > > > Ok, that's not too bad then. Is there actually a reason to still > > > support full-lto > > > in your series? As I understand it, full LTO was the initial approach and > > > used to work better, but thin LTO is actually what we want to use in the > > > long run. Perhaps dropping the full LTO option from your series now > > > that thin LTO works well enough and uses less resources would help > > > avoid some of the problems. > > > > While all developers agree that ThinLTO is a much more palatable > > experience than full LTO; our product teams prefer the excessive build > > time and memory high water mark (at build time) costs in exchange for > > slightly better performance than ThinLTO in > told are important>. Keeping support for full LTO in tree would help > > our product teams reduce the amount of out of tree code they have. As > > long as help > > sell/differentiate phones, I suspect our product teams will continue > > to ship full LTO in production. > > Ok, fair enough. How about marking FULL_LTO as 'depends on > !COMPILE_TEST' then? I'll do that locally for my randconfig tests, > but it would help the other build bots that also force-enable > COMPILE_TEST. Sure, that sounds reasonable to me. I'll add it in v9. Sami _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel 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=-13.2 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 97489C4361B for ; Wed, 9 Dec 2020 16:12:07 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 5322A23A02 for ; Wed, 9 Dec 2020 16:12:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5322A23A02 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-20556-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 5471 invoked by uid 550); 9 Dec 2020 16:11:26 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 5412 invoked from network); 9 Dec 2020 16:11:25 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=RAzf84xm2mgxYvHDSz3COzuojd6IcnSxMMVRpqKMx58=; b=gIACvSNIaNgfk8yYU6S+oPUv61DEJWlMah84jEakzPWNcyXSQgGfZRUQCmTA2z2H68 OBzeyFblbpXMDN4KMc97LtU39WqbsHFa8AfAomXUSKTieYHPNM7GEZ6ZC1XAJfkKWHDD N/rGmO7I1HBChFKlMvhDUHT+DD0u7soRUGjQ6XTsXx6XX9hNVWvtKbx0EmKVXSx0x63q uSx0K2QC6qZIjcT/Vy+GTkse17WcJ35wK97vuG6odXGIYTCqk24f8kQwlYGGa1smU8sB zozuG5IW1kXDMdiObqppDeT7967KYlhg+uX66AupNL004gGWmHXS7ElwVjsdgyVqwHeF qKYA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=RAzf84xm2mgxYvHDSz3COzuojd6IcnSxMMVRpqKMx58=; b=rHv8dB7/+KjClr6CvEciPESTV6QNItIMFHA7J7H2xNUV56ptuhNo5Z8A9MW4CMPSXY 909R3XlkoPUoss2WRTI+lLsGDl1+Xt/PngF+MIuqTCuTsWfZ/JjYvZVBw1mkWhwTW5GQ w7neVIltlyLdg9rzi4bmxaqPqSNOLXCC/SGbAqeaRZrwOfi/TZGiyPU1eCTwXTc90aWE b5OVJcxZObijHa90BGeIVNEOH96d9dKtc/4tpWjhOV8Wyo+aWxaLftaQwhLv02R2lmoD CZgbmX/71x+iaNxXowImQyzaIJwuLh37392BOyI8Kp4rTh4ClkrjBZGU0BGaL63Udcbk m4lQ== X-Gm-Message-State: AOAM533P9Kn50yBEjQ+prePYmcK1NqnxkNth9JIqCwsRpXnZCa3kuMku opvqSSypQG0YsVguA+Wa05H0+r/k0cJ8GBwoG1FK+g== X-Google-Smtp-Source: ABdhPJxCOtYM6wE6I23ECIs2Qe4RqO9Fsld+KWhukNaUvLqxacy6A4k/Hk6QX5PPXhxx/JBHh4wZPl2Wms4urz4X8pg= X-Received: by 2002:ab0:1c0a:: with SMTP id a10mr2343531uaj.89.1607530273519; Wed, 09 Dec 2020 08:11:13 -0800 (PST) MIME-Version: 1.0 References: <20201201213707.541432-1-samitolvanen@google.com> In-Reply-To: From: Sami Tolvanen Date: Wed, 9 Dec 2020 08:11:02 -0800 Message-ID: Subject: Re: [PATCH v8 00/16] Add support for Clang LTO To: Arnd Bergmann Cc: Nick Desaulniers , Masahiro Yamada , Steven Rostedt , Will Deacon , Josh Poimboeuf , Peter Zijlstra , Greg Kroah-Hartman , "Paul E. McKenney" , Kees Cook , clang-built-linux , Kernel Hardening , linux-arch , Linux ARM , Linux Kbuild mailing list , "linux-kernel@vger.kernel.org" , linux-pci Content-Type: text/plain; charset="UTF-8" On Tue, Dec 8, 2020 at 2:20 PM Arnd Bergmann wrote: > > On Tue, Dec 8, 2020 at 10:10 PM 'Nick Desaulniers' via Clang Built > Linux wrote: > > > > On Tue, Dec 8, 2020 at 1:00 PM Arnd Bergmann wrote: > > > > > > On Tue, Dec 8, 2020 at 5:43 PM 'Sami Tolvanen' via Clang Built Linux > > > wrote: > > > > > > > > On Tue, Dec 8, 2020 at 4:15 AM Arnd Bergmann wrote: > > > > > > > > > > - one build seems to take even longer to link. It's currently at 35GB RAM > > > > > usage and 40 minutes into the final link, but I'm worried it might > > > > > not complete > > > > > before it runs out of memory. I only have 128GB installed, and google-chrome > > > > > uses another 30GB of that, and I'm also doing some other builds in parallel. > > > > > Is there a minimum recommended amount of memory for doing LTO builds? > > > > > > > > When building arm64 defconfig, the maximum memory usage I measured > > > > with ThinLTO was 3.5 GB, and with full LTO 20.3 GB. I haven't measured > > > > larger configurations, but I believe LLD can easily consume 3-4x that > > > > much with full LTO allyesconfig. > > > > > > Ok, that's not too bad then. Is there actually a reason to still > > > support full-lto > > > in your series? As I understand it, full LTO was the initial approach and > > > used to work better, but thin LTO is actually what we want to use in the > > > long run. Perhaps dropping the full LTO option from your series now > > > that thin LTO works well enough and uses less resources would help > > > avoid some of the problems. > > > > While all developers agree that ThinLTO is a much more palatable > > experience than full LTO; our product teams prefer the excessive build > > time and memory high water mark (at build time) costs in exchange for > > slightly better performance than ThinLTO in > told are important>. Keeping support for full LTO in tree would help > > our product teams reduce the amount of out of tree code they have. As > > long as help > > sell/differentiate phones, I suspect our product teams will continue > > to ship full LTO in production. > > Ok, fair enough. How about marking FULL_LTO as 'depends on > !COMPILE_TEST' then? I'll do that locally for my randconfig tests, > but it would help the other build bots that also force-enable > COMPILE_TEST. Sure, that sounds reasonable to me. I'll add it in v9. Sami