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=-0.8 required=3.0 tests=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 9C131C33CB2 for ; Wed, 29 Jan 2020 11:10:01 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 47BFD207FD for ; Wed, 29 Jan 2020 11:10:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lca.pw header.i=@lca.pw header.b="VJ8O0yAW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 47BFD207FD Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lca.pw Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id C16986B0007; Wed, 29 Jan 2020 06:10:00 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id BC8326B0008; Wed, 29 Jan 2020 06:10:00 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A67B36B000A; Wed, 29 Jan 2020 06:10:00 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0065.hostedemail.com [216.40.44.65]) by kanga.kvack.org (Postfix) with ESMTP id 90E8E6B0007 for ; Wed, 29 Jan 2020 06:10:00 -0500 (EST) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 536D1181AEF10 for ; Wed, 29 Jan 2020 11:10:00 +0000 (UTC) X-FDA: 76430402160.27.part00_1d14b74ce3b31 X-HE-Tag: part00_1d14b74ce3b31 X-Filterd-Recvd-Size: 6982 Received: from mail-qv1-f66.google.com (mail-qv1-f66.google.com [209.85.219.66]) by imf31.hostedemail.com (Postfix) with ESMTP for ; Wed, 29 Jan 2020 11:09:59 +0000 (UTC) Received: by mail-qv1-f66.google.com with SMTP id dp13so7794492qvb.7 for ; Wed, 29 Jan 2020 03:09:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lca.pw; s=google; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=Rdg0eRE4Rs/tOFVa1nKjmhUlRl2NKOMw55LDI32OSOc=; b=VJ8O0yAWe2cXlzCT1mNhPcxqqFeCKhkmfpyAWfq4oYf0VFJ3BC4CHwckKloSIN0EXg v5DJKr5FfAbivbt4bmiixvzRDbgAX4zdyDY3Z7zJENEidZcJ7qqrRNPRT7y2J7WlkuAW ewW0RwL5VtfuLoAx485pn8lnifxaC15SKUc8607bIEelaurpzyi5k7hkoO7yxuV3yb4d hRnFShBFGIfDCfAPvTiAO0yxsNG/bViMXer6WnGqfUy8ySyDKJC0Q4H5WpZ3O51VPBPp 7I+z1htSl8yn6YxMeGxxXZDeFn0jXFFJZ2cfPzD73Zg0RLbASOFkEZ8dO14ZZO1X4gAp ELnw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=Rdg0eRE4Rs/tOFVa1nKjmhUlRl2NKOMw55LDI32OSOc=; b=HfvSx2E8UD/Urcc6qTA9FWqDg2411KZAlnWOfUTYSlhjwv96zUpUvZNx/n4jQC4JJQ z/UUFEru7jdpLWaUZWzzw1gKvaTE0awsSaZnmAuWrQfNgms3EFBprZ9+xgrFBBbWLn84 fm5Q7aZy22QLnxeOW+ZGWig7L2jm+7ZID6jgv8KjRbEJX/45XNjPehJ2mAQlY9wJz8+l BjfHLX+XxtPvvZ6zMEzMOfj+QLFJVh5lZWOs4jVZKzg+UYCm2hlftVcFIVVtcqKJN+zl vFNqJywQjMd/sZ3rDBymrsanUvH7pCfS+xQh6nD969t7Tmkd/NOtWfcUBb6lRomlOKAG e8yA== X-Gm-Message-State: APjAAAXTW7tAPMvJyFdmMhwSy2xerb9PExKd5Ma6eZfc3eqxuE2KEB9y 0CygZlNBx2SPG4HnK3O6TOtvwks9ZKvuBQ== X-Google-Smtp-Source: APXvYqwSo4IdEjgBam29nZ7sdiS8q0FjVa1Z465Vm5JMHa3pbBcFWxe+wcLkVFwcg7WF0RMbdVCuCg== X-Received: by 2002:a0c:9d4f:: with SMTP id n15mr22120161qvf.194.1580296199181; Wed, 29 Jan 2020 03:09:59 -0800 (PST) Received: from [192.168.1.153] (pool-71-184-117-43.bstnma.fios.verizon.net. [71.184.117.43]) by smtp.gmail.com with ESMTPSA id v7sm882184qtk.89.2020.01.29.03.09.57 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 29 Jan 2020 03:09:58 -0800 (PST) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 13.0 \(3608.40.2.2.4\)) Subject: Re: [PATCH V12] mm/debug: Add tests validating architecture page table helpers From: Qian Cai In-Reply-To: <20200129103640.GA668562@arrakis.emea.arm.com> Date: Wed, 29 Jan 2020 06:09:56 -0500 Cc: Mark Rutland , linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Peter Zijlstra , James Hogan , Heiko Carstens , Michal Hocko , Linux-MM , Paul Mackerras , sparclinux@vger.kernel.org, Ingo Molnar , linux-s390@vger.kernel.org, Jason Gunthorpe , Michael Ellerman , Vlastimil Babka , the arch/x86 maintainers , Russell King - ARM Linux , Matthew Wilcox , Steven Price , Tetsuo Handa , linux-arm-kernel@lists.infradead.org, linux-snps-arc@lists.infradead.org, Kees Cook , Anshuman Khandual , Masahiro Yamada , Dan Williams , Mark Brown , "Kirill A . Shutemov" , Thomas Gleixner , Gerald Schaefer , Christophe Leroy , Sri Krishna chowdary , Dave Hansen , Greg Kroah-Hartman , Ard Biesheuvel , linux-mips@vger.kernel.org, Ralf Baechle , linux-kernel@vger.kernel.org, Paul Burton , Mike Rapoport , Vineet Gupta , Martin Schwidefsky , Andrew Morton , linuxppc-dev@lists.ozlabs.org, "David S. Miller" Content-Transfer-Encoding: quoted-printable Message-Id: <50B7EFFE-1FF0-4B16-84A1-D851052B18B4@lca.pw> References: <20200128174709.GK655507@arrakis.emea.arm.com> <69091BA4-18C4-4425-A5E2-31FBE4654AF9@lca.pw> <20200129103640.GA668562@arrakis.emea.arm.com> To: Catalin Marinas X-Mailer: Apple Mail (2.3608.40.2.2.4) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > On Jan 29, 2020, at 5:36 AM, Catalin Marinas = wrote: >=20 > On Tue, Jan 28, 2020 at 02:07:10PM -0500, Qian Cai wrote: >> On Jan 28, 2020, at 12:47 PM, Catalin Marinas = wrote: >>> The primary goal here is not finding regressions but having clearly >>> defined semantics of the page table accessors across architectures. = x86 >>> and arm64 are a good starting point and other architectures will be >>> enabled as they are aligned to the same semantics. >>=20 >> This still does not answer the fundamental question. If this test is >> simply inefficient to find bugs, >=20 > Who said this is inefficient (other than you)? Inefficient of finding bugs. It said only found a bug or two in its = lifetime? >=20 >> who wants to spend time to use it regularly?=20 >=20 > Arch maintainers, mm maintainers introducing new macros or assuming > certain new semantics of the existing macros. >=20 >> If this is just one off test that may get running once in a few years >> (when introducing a new arch), how does it justify the ongoing cost = to >> maintain it? >=20 > You are really missing the point. It's not only for a new arch but > changes to existing arch code. And if the arch code churn in this area > is relatively small, I'd expect a similarly small cost of maintaining > this test. >=20 > If you only turn DEBUG_VM on once every few years, don't generalise = this > to the rest of the kernel developers (as others pointed out, this test > is default y if DEBUG_VM). Quite the opposite, I am running DEBUG_VM almost daily for regression workload while I felt strongly this thing does not add any value mixing = there. So, I would suggest to decouple this away from DEBUG_VM, and clearly document that this test is not something intended for automated = regression workloads, so those people don=E2=80=99t need to waste time running = this. >=20 > Anyway, I think that's a pointless discussion, so not going to reply > further (unless you have technical content to add). >=20 > --=20 > Catalin