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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 98162EB64DC for ; Fri, 21 Jul 2023 15:08:30 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 33D2D6B0078; Fri, 21 Jul 2023 11:08:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2EE076B007B; Fri, 21 Jul 2023 11:08:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 18E5A8D0001; Fri, 21 Jul 2023 11:08:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 0CB936B0078 for ; Fri, 21 Jul 2023 11:08:30 -0400 (EDT) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id BBBF1A0253 for ; Fri, 21 Jul 2023 15:08:29 +0000 (UTC) X-FDA: 81035950338.14.567586A Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf15.hostedemail.com (Postfix) with ESMTP id 8B83AA003B for ; Fri, 21 Jul 2023 15:08:17 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=HwZSLzxi; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf15.hostedemail.com: domain of vschneid@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=vschneid@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1689952097; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=SD81e7NZBdmvFs/0moOEoRHsNzw2ypppSDOfYt+K9oA=; b=0rpWBqezhEh80NGPTL1A8/IaFFJeegJIQ4w/78YgkUsOIQ42wbIqZWN+y9TirZS+gF3ILM hCMncKN+t0IR/NXGI9KZMeNY6Fq0vGuwqLHDiB86SNuSw6a6Nitla+Ny2WEeaAmKwI+yod KeEVSb/YBWCpV7wXQis1Z7CKi0mngCA= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=HwZSLzxi; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf15.hostedemail.com: domain of vschneid@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=vschneid@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1689952097; a=rsa-sha256; cv=none; b=uJSSf25ahS0Ok2fbnfa1WJCp9fNxzUxPufmG/jgePedxZ1xoW1q5nrhY6HqlWXKgF055q7 5ZFnvQbBTxVc4aFWNUjtkVSZaZes5xCVzUN5t+WF0wuA0m7ymcB64QobGI7u4EleG0g6Dm um4dbgTdTJy0FzSN2l3VoQYayQ8cgUo= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1689952096; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=SD81e7NZBdmvFs/0moOEoRHsNzw2ypppSDOfYt+K9oA=; b=HwZSLzxi0P1oAdGrffqa8WSat0EVVskjrWXXVBpZ8+doOSiy6LZnGhz0tGpLx9EuROcd+x HbqZeBdo/ARZ+i1IfjwKh5Xu4Wzj20gsYUL/ulclIRpCYM9j8D2YOfVSOOuErRfbLmutU+ +7cbCnryJszXJUl5lmN+702Ri+DIMYs= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-564-KT8FznFzOX2MG8zB5xeQEA-1; Fri, 21 Jul 2023 11:08:15 -0400 X-MC-Unique: KT8FznFzOX2MG8zB5xeQEA-1 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-3fc08d6a40cso10761955e9.0 for ; Fri, 21 Jul 2023 08:08:15 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1689952094; x=1690556894; h=mime-version:message-id:date:references:in-reply-to:subject:cc:to :from:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=SD81e7NZBdmvFs/0moOEoRHsNzw2ypppSDOfYt+K9oA=; b=b2M/9kTxqxhoD/EGUdXGJucAvM+ujneDrcGx+V+yphCo2cBxDIkBIi8qWOoabVrFUB JB9h66wljWShdIgQYxFAdwT1ZZpc4fmmV/SQK/97gjyHAoGQnKbhwkVVwmmwv2RJkyIf 4S9oM5XKVDJV7xnNNOVE5e+4TZ/VuavtkmVhivQ97/+BmY8W2aftPkcWamu0APIHbm5y gUoiP6GtTb/OJ3I0ofrXvqaKbkivGPgdftX1ARmLSXhdHiqsmJ219Eezr79cmIuLRVxQ a0Yfzn9c6RM26+cr0KjBq3hymf8n5YapHHtetSmKm0MOjsX9p7gV+HJx1oA0jfnepDk5 rmbA== X-Gm-Message-State: ABy/qLaw0vxHWVehIK72hJB0zYAebQ8knk+tr1ZhvcjqHmRhP3NnBuGB b7sRBrny0oGNQsXQnp4FPQdiEQmirT+5OEwf7K9SyjwqjUflJpc2z+hRbvWEYIfL5OVUuQJlAVC Sh2KBO7dWDRo= X-Received: by 2002:a7b:c455:0:b0:3fc:627:ea31 with SMTP id l21-20020a7bc455000000b003fc0627ea31mr1714692wmi.38.1689952094111; Fri, 21 Jul 2023 08:08:14 -0700 (PDT) X-Google-Smtp-Source: APBJJlF9fiPWFBcIAw2j2QV4lTYmt4mtAVTwBGD8BbL2O21cgVm0IYBel5tSTfnfWuFcEvQp7qgXww== X-Received: by 2002:a7b:c455:0:b0:3fc:627:ea31 with SMTP id l21-20020a7bc455000000b003fc0627ea31mr1714619wmi.38.1689952093765; Fri, 21 Jul 2023 08:08:13 -0700 (PDT) Received: from vschneid.remote.csb ([149.12.7.81]) by smtp.gmail.com with ESMTPSA id q7-20020a5d5747000000b0031434936f0dsm4459951wrw.68.2023.07.21.08.08.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Jul 2023 08:08:12 -0700 (PDT) From: Valentin Schneider To: paulmck@kernel.org Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org, x86@kernel.org, rcu@vger.kernel.org, linux-kselftest@vger.kernel.org, Steven Rostedt , Masami Hiramatsu , Jonathan Corbet , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Paolo Bonzini , Wanpeng Li , Vitaly Kuznetsov , Andy Lutomirski , Peter Zijlstra , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Andrew Morton , Uladzislau Rezki , Christoph Hellwig , Lorenzo Stoakes , Josh Poimboeuf , Jason Baron , Kees Cook , Sami Tolvanen , Ard Biesheuvel , Nicholas Piggin , Juerg Haefliger , Nicolas Saenz Julienne , "Kirill A. Shutemov" , Nadav Amit , Dan Carpenter , Chuang Wang , Yang Jihong , Petr Mladek , "Jason A. Donenfeld" , Song Liu , Julian Pidancet , Tom Lendacky , Dionna Glaze , Thomas =?utf-8?Q?Wei=C3=9Fschuh?= , Juri Lelli , Daniel Bristot de Oliveira , Marcelo Tosatti , Yair Podemsky Subject: Re: [RFC PATCH v2 16/20] rcu: Make RCU dynticks counter size configurable In-Reply-To: <28d4abb7-8496-45ec-b270-ea2b6164537b@paulmck-laptop> References: <20230720163056.2564824-1-vschneid@redhat.com> <20230720163056.2564824-17-vschneid@redhat.com> <28d4abb7-8496-45ec-b270-ea2b6164537b@paulmck-laptop> Date: Fri, 21 Jul 2023 16:08:10 +0100 Message-ID: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 8B83AA003B X-Stat-Signature: psgj7cwwenozzudk8j3tpwepd75qgwwi X-HE-Tag: 1689952097-118567 X-HE-Meta: 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 QEMOCqQF M47VzLsTl5DhK8zuQjq8mZWb7lc0EhRLRp11g//0rCdw2FljPi7Fuq5fjzsHOS6rE+vJnrx4Brog+0Hiw4vrtC+1qs+ZB5Uc6DH8xaN7Dfkt0FGR0VUo7cFRhbYrOvF0PCZ5hgvxO/ZpuntW6y0WYYgQ8SfLfigprQtcXlfcosD4uzgqz7BPOvlyEUqWzjNp5U0gxr9eIgYzCfggZaJQKWeJVO74hb5TNqBEkGV60VgMr57CPxhnsx8gJRPoBHB0XlnPXJBUC15DC8VFtsrT2T2wf63SAS9MxmV4/nksg0mjv42DjvCV/9/ACA3cetHaOd9deXjXtViZNNurSTGVVZTTU/g== 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 21/07/23 07:10, Paul E. McKenney wrote: > On Fri, Jul 21, 2023 at 09:17:53AM +0100, Valentin Schneider wrote: >> On 20/07/23 17:30, Valentin Schneider wrote: >> > index bdd7eadb33d8f..1ff2aab24e964 100644 >> > --- a/kernel/rcu/Kconfig >> > +++ b/kernel/rcu/Kconfig >> > @@ -332,4 +332,37 @@ config RCU_DOUBLE_CHECK_CB_TIME >> > Say Y here if you need tighter callback-limit enforcement. >> > Say N here if you are unsure. >> > >> > +config RCU_DYNTICKS_RANGE_BEGIN >> > + int >> > + depends on !RCU_EXPERT >> > + default 31 if !CONTEXT_TRACKING_WORK >> >> You'll note that this should be 30 really, because the lower *2* bits are >> taken by the context state (CONTEXT_GUEST has a value of 3). >> >> This highlights the fragile part of this: the Kconfig values are hardcoded, >> but they depend on CT_STATE_SIZE, CONTEXT_MASK and CONTEXT_WORK_MAX. The >> static_assert() will at least capture any misconfiguration, but having that >> enforced by the actual Kconfig ranges would be less awkward. >> >> Do we currently have a way of e.g. making a Kconfig file depend on and use >> values generated by a C header? > > Why not just have something like a boolean RCU_DYNTICKS_TORTURE Kconfig > option and let the C code work out what the number of bits should be? > > I suppose that there might be a failure whose frequency depended on > the number of bits, which might be an argument for keeping something > like RCU_DYNTICKS_RANGE_BEGIN for fault isolation. But still using > RCU_DYNTICKS_TORTURE for normal testing. > > Thoughts? > AFAICT if we run tests with the minimum possible width, then intermediate values shouldn't have much value. Your RCU_DYNTICKS_TORTURE suggestion sounds like a saner option than what I came up with, as we can let the context tracking code figure out the widths itself and not expose any of that to Kconfig. > Thanx, Paul