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=-5.8 required=3.0 tests=BAYES_00,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 C71C2C43460 for ; Mon, 17 May 2021 20:48:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A1AC961185 for ; Mon, 17 May 2021 20:48:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233214AbhEQUtx (ORCPT ); Mon, 17 May 2021 16:49:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41818 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229776AbhEQUtx (ORCPT ); Mon, 17 May 2021 16:49:53 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 31F46C061573; Mon, 17 May 2021 13:48:36 -0700 (PDT) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1621284514; 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; bh=N9j0B7b156ySsfMwDJsNRd7Lot/GWP1durNGX4F30bE=; b=1ZpNYLsTCuxDd2w4It1l3dHPjwwAqXAEgSY+DEPNfEPoHcR+Tj8HSX/lM6OuPLk7dDZQVW W1mANCzHmyx/moYnbSqJIsfksQzHubt7JiZM2zKDIcbWHzozO2ubMZ64DlHO+vvi6SI3/u kzgUMF1r1LiMVSf6GAg4a80TbFVuMBAThFvwPAqShd0TKE41wvAv3ecwduS+Wu1jdbDg0I AbAfl/Kx/MAGDQmSaMwvUS+//Ee8ZAgjroZ+SaUJfqQ5dTIfSI6X60+ohc6ZLvj7Z1TR8t CqFlk/za3NV3QACI21PFNIS7CqVMAmhb4Di/XCXQ8oCYUumaEBmQw4P267xG8Q== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1621284514; 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; bh=N9j0B7b156ySsfMwDJsNRd7Lot/GWP1durNGX4F30bE=; b=Cq5gGnOum9YEtmqRoidToVZ0cJKjg3O1ZDCn247dy6VTZmmSgwiY8J34jS0r/5mY/3Ru7v WBWf4Bc9muZaDeDA== To: Jesse Brandeburg , Robin Murphy Cc: 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 , abelits@marvell.com, "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, Nitesh Lal , Marc Zyngier Subject: Re: [PATCH tip:irq/core v1] genirq: remove auto-set of the mask when setting the hint In-Reply-To: <20210504092340.00006c61@intel.com> Date: Mon, 17 May 2021 22:48:33 +0200 Message-ID: <87pmxpdr32.ffs@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Tue, May 04 2021 at 09:23, Jesse Brandeburg wrote: > I'd add in addition that irqbalance daemon *stopped* paying attention > to hints quite a while ago, so I'm not quite sure what purpose they > serve. 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? 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... While none of the drivers (except the perf muck) actually prevents userspace from fiddling with the affinity (via IRQF_NOBALANCING) a deeper inspection shows that they actually might rely on the current behaviour if irqbalanced is disabled. Of course every driver has its own convoluted way to do that and all of those functions are well documented. What a mess. If the hint still serves a purpose then we can provide a variant which solely applies the hint and does not fiddle with the actual affinity, but if the hint is useless anyway then we have a way better option to clean that up. Most users are in networking, there are a few in crypto, a couple of leftovers in scsi, virtio and a handfull of oddball drivers. The perf muck wants to be cleaned up anyway as it's just crystal clear abuse. Thanks, tglx