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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 DFDA0C43144 for ; Fri, 22 Jun 2018 15:10:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A57AE24475 for ; Fri, 22 Jun 2018 15:10:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A57AE24475 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754420AbeFVPKO (ORCPT ); Fri, 22 Jun 2018 11:10:14 -0400 Received: from mga04.intel.com ([192.55.52.120]:45065 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754363AbeFVPKL (ORCPT ); Fri, 22 Jun 2018 11:10:11 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 22 Jun 2018 08:10:10 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.51,257,1526367600"; d="scan'208";a="51089334" Received: from rshibano-mobl.amr.corp.intel.com (HELO [10.252.132.223]) ([10.252.132.223]) by orsmga007.jf.intel.com with ESMTP; 22 Jun 2018 08:10:09 -0700 Subject: Re: [PATCH 1/7] mm: allocate mm_cpumask dynamically based on nr_cpu_ids To: Rik van Riel , linux-kernel@vger.kernel.org References: <20180620195652.27251-1-riel@surriel.com> <20180620195652.27251-2-riel@surriel.com> Cc: luto@kernel.org, mingo@kernel.org, tglx@linutronix.de, efault@gmx.de, songliubraving@fb.com, kernel-team@fb.com From: Dave Hansen Openpgp: preference=signencrypt Autocrypt: addr=dave.hansen@linux.intel.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <20180620195652.27251-2-riel@surriel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/20/2018 12:56 PM, Rik van Riel wrote: > /* > - * FIXME! The "sizeof(struct mm_struct)" currently includes the > - * whole struct cpumask for the OFFSTACK case. We could change > - * this to *only* allocate as much of it as required by the > - * maximum number of CPU's we can ever have. The cpumask_allocation > - * is at the end of the structure, exactly for that reason. > + * The mm_cpumask is located at the end of mm_struct, and is > + * dynamically sized based on nr_cpu_ids. > */ > + mm_size = sizeof(struct mm_struct) + cpumask_size(); > + > mm_cachep = kmem_cache_create_usercopy("mm_struct", > - sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, > + mm_size, ARCH_MIN_MMSTRUCT_ALIGN, Could you add a bit to that comment, like "dynamically sized based on nr_cpu_ids" ... which is sized based on the number of possible CPUs. I found myself wondering how that interacts with hotplug. t mm_struct, saved_auxv), > diff --git a/mm/init-mm.c b/mm/init-mm.c > index f94d5d15ebc0..20fe222fe4c0 100644 > --- a/mm/init-mm.c > +++ b/mm/init-mm.c > @@ -15,6 +15,15 @@ > #define INIT_MM_CONTEXT(name) > #endif > > +/* > + * For dynamically allocated mm_structs, there is a dynamically sized cpumask > + * at the end of the structure, the size of which depends on nr_cpu_ids. That... Similar nit. Instead of calling out the variable alone, could we just say what it means logically and then reference the variable?