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=-6.1 required=3.0 tests=BAYES_00,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 45DD7C43461 for ; Tue, 18 May 2021 00:23:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 25C2461370 for ; Tue, 18 May 2021 00:23:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235539AbhERAYl (ORCPT ); Mon, 17 May 2021 20:24:41 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:36648 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244329AbhERAYj (ORCPT ); Mon, 17 May 2021 20:24:39 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1621297401; 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=1CFhwAdeADWfjY+TeEUXI0dttR2qRWxmhTMkaKMBCuk=; b=QCkR1k9lR/70CJKPoAFt9x5QQS+GMehcmBzYCi9u0Dlg5Ob+SCooPjB7WnwC/c3DrSarOY YV300nEhEodxRtiZOi03dM1Lzw0YL93zz07I8BCb9qYUxWI5fM2bxxOehLL165LOfVO5Px l/ZPEqZ1bQwT/hK3VZT+OsRngPAY+aY= Received: from mail-lj1-f197.google.com (mail-lj1-f197.google.com [209.85.208.197]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-148-8UC_-8F_Mdy5MlkDa8FANw-1; Mon, 17 May 2021 20:23:18 -0400 X-MC-Unique: 8UC_-8F_Mdy5MlkDa8FANw-1 Received: by mail-lj1-f197.google.com with SMTP id k1-20020a2e88810000b02900c00f378c5cso3856017lji.7 for ; Mon, 17 May 2021 17:23:18 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=1CFhwAdeADWfjY+TeEUXI0dttR2qRWxmhTMkaKMBCuk=; b=UEYPKYAajgLqgPONurlxsv7FZwEFgqPAst9vsVQDRyUXGtuE8DSdO5qkh7k5cTqris yv51wa0tvG9QDMOyFCzIXkXahbgRWeDICEyz4Wgfhh4h9VL1FVq0g13H3wZ6thpPuvQ/ 4U13N4OCBcpCTLOYqHzgv7M6QQy43QND8vZ+1A++IWD6e6VhjjI4y1sK0kQH/duwRDgW H7Yh9/QWWVfI2nz+HwS6x99cXEM5ryCUPhwVcRC9uRFU8/yT4AetbI08870q4hRLxuRS YntySGvFjeY8OsldGydDQwAThQsE6wNrJHAZeAgn01ScZZcWt/14ZWzfqTZI4dG/FZ7k spFw== X-Gm-Message-State: AOAM533ZPSK23WuHmbgG8p4Q/Bn/tzLwWewG9RRi6CbdGqHZ1wDRHW70 oioIOWP9S2fjnmHxyEKjv6HbxWISAUrCfHA4ZNyYKe7A6ogLfWD6QJhsuz/QQ+GCyCrRJl2v+Gi xOR/QIUx1RwXS4YqxO1VbuDNT20tRdi+hNyPd X-Received: by 2002:a05:6512:3da1:: with SMTP id k33mr1954932lfv.114.1621297396826; Mon, 17 May 2021 17:23:16 -0700 (PDT) X-Google-Smtp-Source: ABdhPJyhOM/aeHK0aO1U0IXX7Bz97GQL+BiXI9gjCeNpT1VQx45C+gwAHC4wQS/KVuaPU2Um6MqyAaMyIDDi2YeTCBA= X-Received: by 2002:a05:6512:3da1:: with SMTP id k33mr1954902lfv.114.1621297396624; Mon, 17 May 2021 17:23:16 -0700 (PDT) MIME-Version: 1.0 References: <20210504092340.00006c61@intel.com> <87pmxpdr32.ffs@nanos.tec.linutronix.de> <87im3gewlu.ffs@nanos.tec.linutronix.de> In-Reply-To: <87im3gewlu.ffs@nanos.tec.linutronix.de> From: Nitesh Lal Date: Mon, 17 May 2021 20:23:05 -0400 Message-ID: Subject: Re: [PATCH tip:irq/core v1] genirq: remove auto-set of the mask when setting the hint To: Thomas Gleixner Cc: Jesse Brandeburg , Robin Murphy , Ingo Molnar , linux-kernel@vger.kernel.org, intel-wired-lan@lists.osuosl.org, jbrandeb@kernel.org, "frederic@kernel.org" , "juri.lelli@redhat.com" , Marcelo Tosatti , Alex Belits , "linux-api@vger.kernel.org" , "bhelgaas@google.com" , "linux-pci@vger.kernel.org" , "rostedt@goodmis.org" , "peterz@infradead.org" , "davem@davemloft.net" , "akpm@linux-foundation.org" , "sfr@canb.auug.org.au" , "stephen@networkplumber.org" , "rppt@linux.vnet.ibm.com" , "jinyuqi@huawei.com" , "zhangshaokun@hisilicon.com" , netdev@vger.kernel.org, chris.friesen@windriver.com, Marc Zyngier , Neil Horman , pjwaskiewicz@gmail.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Mon, May 17, 2021 at 8:04 PM Thomas Gleixner wrote: > > On Mon, May 17 2021 at 18:44, Nitesh Lal wrote: > > On Mon, May 17, 2021 at 4:48 PM Thomas Gleixner wrote: > >> The hint was added so that userspace has a better understanding where it > >> should place the interrupt. So if irqbalanced ignores it anyway, then > >> what's the point of the hint? IOW, why is it still used drivers? > >> > > Took a quick look at the irqbalance repo and saw the following commit: > > > > dcc411e7bf remove affinity_hint infrastructure > > > > The commit message mentions that "PJ is redesiging how affinity hinting > > works in the kernel, the future model will just tell us to ignore an IRQ, > > and the kernel will handle placement for us. As such we can remove the > > affinity_hint recognition entirely". > > No idea who PJ is. I really love useful commit messages. Maybe Neil can > shed some light on that. > > > This does indicate that apparently, irqbalance moved away from the usage of > > affinity_hint. However, the next question is what was this future > > model? > > I might have missed something in the last 5 years, but that's the first > time I hear about someone trying to cleanup that thing. > > > I don't know but I can surely look into it if that helps or maybe someone > > here already knows about it? > > I CC'ed Neil :) Thanks, I have added PJ Waskiewicz as well who I think was referred in that commit message as PJ. > > >> Now there is another aspect to that. What happens if irqbalanced does > >> not run at all and a driver relies on the side effect of the hint > >> setting the initial affinity. Bah... > >> > > > > Right, but if they only rely on this API so that the IRQs are spread across > > all the CPUs then that issue is already resolved and these other drivers > > should not regress because of changing this behavior. Isn't it? > > Is that true for all architectures? Unfortunately, I don't know and that's probably why we have to be careful. -- Nitesh