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=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 73ECBC4727C for ; Mon, 28 Sep 2020 23:55:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 36C0A2083B for ; Mon, 28 Sep 2020 23:55:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601337338; bh=0n1xJcdLngQdEbL6h/atc0mGb4YVbGMJlbNqrb3rWc0=; h=Date:From:To:Cc:Subject:In-Reply-To:List-ID:From; b=IwyxDletPwYRIfyRVwRpxRMJnAtSZCHE+KfebnGAsW56fCRhhMXsWfypT4y07V7EK OZwT+U7eS9D+OIDW4+G2Zo7T4x8T8BcT0VJXYs+LEV29gHKNgqomqcKQpHtkw3MnCy tUzsYrOyikrb9I6KaTnOTgkMyfNt+Wdy/yobvJy8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727166AbgI1Xzc (ORCPT ); Mon, 28 Sep 2020 19:55:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:51780 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726522AbgI1Xzc (ORCPT ); Mon, 28 Sep 2020 19:55:32 -0400 Received: from localhost (52.sub-72-107-123.myvzw.com [72.107.123.52]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id BFCA52083B; Mon, 28 Sep 2020 21:59:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601330373; bh=0n1xJcdLngQdEbL6h/atc0mGb4YVbGMJlbNqrb3rWc0=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=TPpxBphvz+2D9Uwv5VqfQh0wF+3Q/7TSzzgny4d7237sTORHdrdkk58bs1BWlGT6v zx70R2QzsjjCdGSPdGWmHX1ifdjxKDGigQo4yWcs4p9sTTOTpGuvhuao0t38NmeFAX O1xWNs/AwwHQU1IqkaFmk4+tPRE2S87hvWuuckTY= Date: Mon, 28 Sep 2020 16:59:31 -0500 From: Bjorn Helgaas To: Nitesh Narayan Lal , hch@infradead.org Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-pci@vger.kernel.org, intel-wired-lan@lists.osuosl.org, frederic@kernel.org, mtosatti@redhat.com, sassmann@redhat.com, jesse.brandeburg@intel.com, lihong.yang@intel.com, jeffrey.t.kirsher@intel.com, jacob.e.keller@intel.com, jlelli@redhat.com, bhelgaas@google.com, mike.marciniszyn@intel.com, dennis.dalessandro@intel.com, thomas.lendacky@amd.com, jiri@nvidia.com, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, lgoncalv@redhat.com Subject: Re: [PATCH v4 4/4] PCI: Limit pci_alloc_irq_vectors() to housekeeping CPUs Message-ID: <20200928215931.GA2499944@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200928183529.471328-5-nitesh@redhat.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org [to: Christoph in case he has comments, since I think he wrote this code] On Mon, Sep 28, 2020 at 02:35:29PM -0400, Nitesh Narayan Lal wrote: > If we have isolated CPUs dedicated for use by real-time tasks, we try to > move IRQs to housekeeping CPUs from the userspace to reduce latency > overhead on the isolated CPUs. > > If we allocate too many IRQ vectors, moving them all to housekeeping CPUs > may exceed per-CPU vector limits. > > When we have isolated CPUs, limit the number of vectors allocated by > pci_alloc_irq_vectors() to the minimum number required by the driver, or > to one per housekeeping CPU if that is larger. > > Signed-off-by: Nitesh Narayan Lal Acked-by: Bjorn Helgaas > --- > drivers/pci/msi.c | 18 ++++++++++++++++++ > 1 file changed, 18 insertions(+) > > diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c > index 30ae4ffda5c1..8c156867803c 100644 > --- a/drivers/pci/msi.c > +++ b/drivers/pci/msi.c > @@ -23,6 +23,7 @@ > #include > #include > #include > +#include > > #include "pci.h" > > @@ -1191,8 +1192,25 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs, > struct irq_affinity *affd) > { > struct irq_affinity msi_default_affd = {0}; > + unsigned int hk_cpus; > int nvecs = -ENOSPC; > > + hk_cpus = housekeeping_num_online_cpus(HK_FLAG_MANAGED_IRQ); > + > + /* > + * If we have isolated CPUs for use by real-time tasks, to keep the > + * latency overhead to a minimum, device-specific IRQ vectors are moved > + * to the housekeeping CPUs from the userspace by changing their > + * affinity mask. Limit the vector usage to keep housekeeping CPUs from > + * running out of IRQ vectors. > + */ > + if (hk_cpus < num_online_cpus()) { > + if (hk_cpus < min_vecs) > + max_vecs = min_vecs; > + else if (hk_cpus < max_vecs) > + max_vecs = hk_cpus; > + } > + > if (flags & PCI_IRQ_AFFINITY) { > if (!affd) > affd = &msi_default_affd; > -- > 2.18.2 >