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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7123FECAAD5 for ; Tue, 6 Sep 2022 16:17:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234680AbiIFQRw (ORCPT ); Tue, 6 Sep 2022 12:17:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39916 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238847AbiIFQRR (ORCPT ); Tue, 6 Sep 2022 12:17:17 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F1C8B6E2C5 for ; Tue, 6 Sep 2022 08:45:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1662479143; 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=UwR9WLlMcOlcjIJvL6VN4UAUczzjG6l4ky/hbJluh+s=; b=W7E+QJrQftbjpgvvaywk0+3JdPW/GV5mKyaq7LHGx9JGRB4dWWCGIS2yju6KKam7lsydzd amoVTWU0Haek8tQ6DtJ3Hn/UiLS2yzE+cKGi//x2cYjN8YsJAEEBgzRok2tjH//Y/dio8j Pg5KVUQOPnFrafnUGRLpB5qkdvilzA4= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-497-lEm8pABVPCWW_M_SGjRtWw-1; Tue, 06 Sep 2022 11:45:41 -0400 X-MC-Unique: lEm8pABVPCWW_M_SGjRtWw-1 Received: by mail-wm1-f69.google.com with SMTP id 203-20020a1c02d4000000b003a5f5bce876so8958613wmc.2 for ; Tue, 06 Sep 2022 08:45:41 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=mime-version:message-id:date:references:in-reply-to:subject:cc:to :from:x-gm-message-state:from:to:cc:subject:date; bh=UwR9WLlMcOlcjIJvL6VN4UAUczzjG6l4ky/hbJluh+s=; b=D8yO68fVN66b5wbykJt79Rngcm20FJl29mW0ZgdxT+JazHjBe8JrsbBgMlGMR7ZoO+ 2QyANDMk0NsziZxyU4pQFTch1UBbYhdSHUHaTvkTxh+T/gt/ff9wFap/CoC1OVuEaFBh X9HpNIfHIbFqaAxfsseKDE1KdaAEWc42HErkBZxzaJxLNGEUHbnmNXKmDJuNJPk4Cza1 yrQBB0Gr/i7yVJUFQngo0GKnG0bS/jc3FaV4WV2QfpN7yhhgbmP1b0VvzJ8B8uXBi7zX 0lA6i/nh7cULAlIkJpyDfSgOdWBV/+NpA8Y+OBKyAt/PplWogDZPLTqUGl6Z+CHYPTtr dgNg== X-Gm-Message-State: ACgBeo3KhM2z46OAopZvDRqG3dBl7fMMQOAfPcBwNQXuiFs6ca1UZQdg y91wAiRPzJ9h/GQSlYT++MX2y+gSb5UESRz6o/++/Ra9sIsLgyCH0AeDCVNQCWwDUEjxCsah7ys l1iezoliOW6+Ok9KcY5KbfoHv X-Received: by 2002:adf:d1e8:0:b0:223:bca:8019 with SMTP id g8-20020adfd1e8000000b002230bca8019mr27334461wrd.562.1662479139553; Tue, 06 Sep 2022 08:45:39 -0700 (PDT) X-Google-Smtp-Source: AA6agR5koLA8Nh5T8MSFtHiXTikfjA2tCMg2n1xwQ9omsbDczQllbiS5uHpSlqayh1h9C3PKVbLPoQ== X-Received: by 2002:adf:d1e8:0:b0:223:bca:8019 with SMTP id g8-20020adfd1e8000000b002230bca8019mr27334451wrd.562.1662479139408; Tue, 06 Sep 2022 08:45:39 -0700 (PDT) Received: from vschneid.remote.csb ([185.11.37.247]) by smtp.gmail.com with ESMTPSA id v22-20020a7bcb56000000b003a5ad7f6de2sm15138039wmj.15.2022.09.06.08.45.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 Sep 2022 08:45:38 -0700 (PDT) From: Valentin Schneider To: Peter Zijlstra Cc: Yury Norov , linux-kernel@vger.kernel.org, Andy Shevchenko , Rasmus Villemoes , Andrew Morton , Stephen Rothwell , Thomas Gleixner , "Paul E . McKenney" , Vlastimil Babka , Dmitry Vyukov , Sander Vanheule , Alexey Klimov , Eric Biggers Subject: Re: [PATCH v2 0/5] cpumask: cleanup nr_cpu_ids vs nr_cpumask_bits mess In-Reply-To: References: <20220905230820.3295223-1-yury.norov@gmail.com> Date: Tue, 06 Sep 2022 16:45:37 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/09/22 16:38, Peter Zijlstra wrote: > On Tue, Sep 06, 2022 at 01:06:47PM +0100, Valentin Schneider wrote: > >> #define nr_cpumask_bits nr_cpu_ids > > That assumes the CPU space is dense; is this so? That is, you can have 4 > CPUs while the highest cpu number is vastly larger than 4. > > It's uncommon, but not unheard of I think. ISTR some BIOSes leaving > holes in the CPU space when there were empty CPU sockets on the > motherboard. I'd assume this would be visible in the cpu_possible_mask and thus be properly reflected in nr_cpu_ids. Otherwise that would already break with CONFIG_CPUMASK_OFFSTACK=y, I think.