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=-11.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 A317DC433E2 for ; Thu, 10 Sep 2020 19:23:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 68B20206DB for ; Thu, 10 Sep 2020 19:23:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="UoOzMGSv" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727908AbgIJTXY (ORCPT ); Thu, 10 Sep 2020 15:23:24 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:31543 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726588AbgIJTXJ (ORCPT ); Thu, 10 Sep 2020 15:23:09 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1599765782; 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=aO5Uccl5Oi5KJ41E3z0pO/LdRmt1WMvp7bc2MBKi/rk=; b=UoOzMGSvwbWInCk+u+9ShoKW5LcZK+mjOID7XFDhIuX6U7Yw3INVhKRTLrDd9XMNbFBulT Ob0NBmaK7gfZR9eaDRvqd2aAFAwsCxgnfSS011AaNhU72OWCYNOpORp+7SrFALM9RvzjUl vOCts1I6nRQ6f9ClIXEdRzLNqQb55bY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-282-nH1tbEipMPOnT8j1YMvhfA-1; Thu, 10 Sep 2020 15:23:00 -0400 X-MC-Unique: nH1tbEipMPOnT8j1YMvhfA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 271FC1008550; Thu, 10 Sep 2020 19:22:58 +0000 (UTC) Received: from fuller.cnet (ovpn-112-5.gru2.redhat.com [10.97.112.5]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CA28360BF4; Thu, 10 Sep 2020 19:22:54 +0000 (UTC) Received: by fuller.cnet (Postfix, from userid 1000) id 2E4E541853FD; Thu, 10 Sep 2020 16:22:08 -0300 (-03) Date: Thu, 10 Sep 2020 16:22:08 -0300 From: Marcelo Tosatti To: Nitesh Narayan Lal Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-pci@vger.kernel.org, frederic@kernel.org, sassmann@redhat.com, jeffrey.t.kirsher@intel.com, jacob.e.keller@intel.com, jlelli@redhat.com, hch@infradead.org, bhelgaas@google.com, mike.marciniszyn@intel.com, dennis.dalessandro@intel.com, thomas.lendacky@amd.com, jerinj@marvell.com, mathias.nyman@intel.com, jiri@nvidia.com Subject: Re: [RFC][Patch v1 3/3] PCI: Limit pci_alloc_irq_vectors as per housekeeping CPUs Message-ID: <20200910192208.GA24845@fuller.cnet> References: <20200909150818.313699-1-nitesh@redhat.com> <20200909150818.313699-4-nitesh@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200909150818.313699-4-nitesh@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 09, 2020 at 11:08:18AM -0400, Nitesh Narayan Lal wrote: > This patch limits the pci_alloc_irq_vectors max vectors that is passed on > by the caller based on the available housekeeping CPUs by only using the > minimum of the two. > > A minimum of the max_vecs passed and available housekeeping CPUs is > derived to ensure that we don't create excess vectors which can be > problematic specifically in an RT environment. This is because for an RT > environment unwanted IRQs are moved to the housekeeping CPUs from > isolated CPUs to keep the latency overhead to a minimum. If the number of > housekeeping CPUs are significantly lower than that of the isolated CPUs > we can run into failures while moving these IRQs to housekeeping due to > per CPU vector limit. > > Signed-off-by: Nitesh Narayan Lal > --- > include/linux/pci.h | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > diff --git a/include/linux/pci.h b/include/linux/pci.h > index 835530605c0d..750ba927d963 100644 > --- a/include/linux/pci.h > +++ b/include/linux/pci.h > @@ -38,6 +38,7 @@ > #include > #include > #include > +#include > #include > > #include > @@ -1797,6 +1798,21 @@ static inline int > pci_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs, > unsigned int max_vecs, unsigned int flags) > { > + unsigned int num_housekeeping = num_housekeeping_cpus(); > + unsigned int num_online = num_online_cpus(); > + > + /* > + * Try to be conservative and at max only ask for the same number of > + * vectors as there are housekeeping CPUs. However, skip any > + * modification to the of max vectors in two conditions: > + * 1. If the min_vecs requested are higher than that of the > + * housekeeping CPUs as we don't want to prevent the initialization > + * of a device. > + * 2. If there are no isolated CPUs as in this case the driver should > + * already have taken online CPUs into consideration. > + */ > + if (min_vecs < num_housekeeping && num_housekeeping != num_online) > + max_vecs = min_t(int, max_vecs, num_housekeeping); > return pci_alloc_irq_vectors_affinity(dev, min_vecs, max_vecs, flags, > NULL); > } If min_vecs > num_housekeeping, for example: /* PCI MSI/MSIx support */ #define XGBE_MSI_BASE_COUNT 4 #define XGBE_MSI_MIN_COUNT (XGBE_MSI_BASE_COUNT + 1) Then the protection fails. How about reducing max_vecs down to min_vecs, if min_vecs > num_housekeeping ?