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=-8.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 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 0BE0DC43461 for ; Thu, 17 Sep 2020 18:34:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B3A6D206B6 for ; Thu, 17 Sep 2020 18:34:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726609AbgIQSdy (ORCPT ); Thu, 17 Sep 2020 14:33:54 -0400 Received: from mga04.intel.com ([192.55.52.120]:27797 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726325AbgIQScs (ORCPT ); Thu, 17 Sep 2020 14:32:48 -0400 X-Greylist: delayed 506 seconds by postgrey-1.27 at vger.kernel.org; Thu, 17 Sep 2020 14:32:42 EDT IronPort-SDR: 7ew2Hb6n78lGQ3CqvJOe1JiPoVu193dtxB2v2OaHWgVNILDosVxvnq8P6UlKCEM2TqmkQaagiP nwN1OtBqaffQ== X-IronPort-AV: E=McAfee;i="6000,8403,9747"; a="157152788" X-IronPort-AV: E=Sophos;i="5.77,271,1596524400"; d="scan'208";a="157152788" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Sep 2020 11:24:00 -0700 IronPort-SDR: yYtdAPkiDQ4SILsHO3HluWV0SOgMmQfmPW+5nbU66OIMIbrUlVibSnpBqoEUSwT69RNxgFV7pi IBD6K8SdIkxw== X-IronPort-AV: E=Sophos;i="5.77,271,1596524400"; d="scan'208";a="483851908" Received: from jbrandeb-mobl3.amr.corp.intel.com (HELO localhost) ([10.251.16.238]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Sep 2020 11:24:00 -0700 Date: Thu, 17 Sep 2020 11:23:59 -0700 From: Jesse Brandeburg To: Nitesh Narayan Lal Cc: , , , , , , , , , , , , , , , , Subject: Re: [RFC][Patch v1 2/3] i40e: limit msix vectors based on housekeeping CPUs Message-ID: <20200917112359.00006e10@intel.com> In-Reply-To: <20200909150818.313699-3-nitesh@redhat.com> References: <20200909150818.313699-1-nitesh@redhat.com> <20200909150818.313699-3-nitesh@redhat.com> X-Mailer: Claws Mail 3.12.0 (GTK+ 2.24.28; i686-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Nitesh Narayan Lal wrote: > In a realtime environment, it is essential to isolate unwanted IRQs from > isolated CPUs to prevent latency overheads. Creating MSIX vectors only > based on the online CPUs could lead to a potential issue on an RT setup > that has several isolated CPUs but a very few housekeeping CPUs. This is > because in these kinds of setups an attempt to move the IRQs to the > limited housekeeping CPUs from isolated CPUs might fail due to the per > CPU vector limit. This could eventually result in latency spikes because > of the IRQ threads that we fail to move from isolated CPUs. > > This patch prevents i40e to add vectors only based on available > housekeeping CPUs by using num_housekeeping_cpus(). > > Signed-off-by: Nitesh Narayan Lal The driver changes are straightforward, but this isn't the only driver with this issue, right? I'm sure ixgbe and ice both have this problem too, you should fix them as well, at a minimum, and probably other vendors drivers: $ rg -c --stats num_online_cpus drivers/net/ethernet ... 50 files contained matches for this patch i40e Acked-by: Jesse Brandeburg