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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 3CB62C35242 for ; Fri, 14 Feb 2020 19:40:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 016DE206CC for ; Fri, 14 Feb 2020 19:40:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="CesTyts3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729927AbgBNTkP (ORCPT ); Fri, 14 Feb 2020 14:40:15 -0500 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:21189 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729633AbgBNTkO (ORCPT ); Fri, 14 Feb 2020 14:40:14 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1581709213; 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=BE9teR/4Mz7yydIxx4Z3k95pTHytQ+QYaa5uCwafbV0=; b=CesTyts35amLfIahLWRnttHtl2bVNYYRmeEW/eSqNMTzdyfIEnzUQEm3wSqz9FRFo6OruV w+fZ8Cm/Bi73HFByzgaHhOxkjSwFQwMWyxcnZ+lT1MMqL9wA1Su17+UqXu5/qdKWFpUfXj 8R0bdcuyEVWzS1WsB3Q1R0zKFqvB6DI= Received: from mail-qv1-f69.google.com (mail-qv1-f69.google.com [209.85.219.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-99-_hLdMz4tN3-qYYc-y7uaow-1; Fri, 14 Feb 2020 14:40:12 -0500 X-MC-Unique: _hLdMz4tN3-qYYc-y7uaow-1 Received: by mail-qv1-f69.google.com with SMTP id p3so6389358qvt.9 for ; Fri, 14 Feb 2020 11:40:12 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=BE9teR/4Mz7yydIxx4Z3k95pTHytQ+QYaa5uCwafbV0=; b=cnoV1Nvd6IkzpFRf/lInClccIrUKtzNWaz8kOhjNkV1vwlYD9yYHU+RSqv2KVtJshr lkclYL/i9FGpUfIjsJqiNqfZohQLvtQEO9F25IWbdxXx+D54hcJwyvDtGpmCu1bGgdbH hKkw1uh+OSb7lp7H5+rDEIVFKWxUV7vR1ck7z/11TNHOsNkL6PZe7or43RgAtxZCZR0l 5RxIN7ZwJXfEzSWTa+onKMtQblEBBzrJvtdeydRWzDMxKycFSAbcAHWcy1i9U8h7LQ6o ywrZkRPIRuEcyFiV7tx1xn/R/GqklXt18JfVIVU+KdVDzOqy19HDFYDWkqEG4wV+/GzX RyAw== X-Gm-Message-State: APjAAAVrbBJbVMw8+3YClkPrOy/LQsYjntXFMsS5haBV1ZvkZEftmnNM VqmFIMAsNRL3xoDZ13/4VFNDhPz3z2mr9lptn4rk7AwHtel5OZF6ZMbJ9kDT1xJpP0bt12sTdXA 4HpGxf9xuGPnQr63gjpN84QIv X-Received: by 2002:a37:c49:: with SMTP id 70mr4265162qkm.12.1581709211258; Fri, 14 Feb 2020 11:40:11 -0800 (PST) X-Google-Smtp-Source: APXvYqwIfgOvyKPo0dPjB9m4JrN4P419c0E8fs0nNBksTNU/4s3Oo9D6YcAB01pS1mSfyNQja16xgg== X-Received: by 2002:a37:c49:: with SMTP id 70mr4265146qkm.12.1581709211022; Fri, 14 Feb 2020 11:40:11 -0800 (PST) Received: from xz-x1 ([104.156.64.74]) by smtp.gmail.com with ESMTPSA id t187sm2583971qke.85.2020.02.14.11.40.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 14 Feb 2020 11:40:09 -0800 (PST) Date: Fri, 14 Feb 2020 14:40:08 -0500 From: Peter Xu To: linux-kernel@vger.kernel.org Cc: Ming Lei , Ingo Molnar , Peter Zijlstra , Juri Lelli , Luiz Capitulino , Thomas Gleixner Subject: Re: [PATCH] sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters Message-ID: <20200214194008.GA1193332@xz-x1> References: <20200204161639.267026-1-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200204161639.267026-1-peterx@redhat.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 04, 2020 at 11:16:39AM -0500, Peter Xu wrote: > The "isolcpus=" parameter allows sub-parameters to exist before the > cpulist is specified, and if it sees unknown sub-parameters the whole > parameter will be ignored. This design is incompatible with itself > when we add more sub-parameters to "isolcpus=", because the old > kernels will not recognize the new "isolcpus=" sub-parameters, then it > will invalidate the whole parameter so the CPU isolation will not > really take effect if we start to use the new sub-parameters while > later we reboot into an old kernel. Instead we will see this when > booting the old kernel: > > isolcpus: Error, unknown flag > > The better and compatible way is to allow "isolcpus=" to skip unknown > sub-parameters, so that even if we add new sub-parameters to it the > old kernel will still be able to behave as usual even if with the new > sub-parameter is specified. > > Ideally this patch should be there when we introduce the first > sub-parameter for "isolcpus=", so it's already a bit late. However > late is better than nothing. Ping - Hi, Thomas, do you have any further comment on this patch? Thanks, -- Peter Xu