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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 BAC75C43331 for ; Fri, 6 Sep 2019 19:01:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 90A12207FC for ; Fri, 6 Sep 2019 19:01:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567796474; bh=Jiz8B43eSk9SxWcQmicR7EYR2TlCQ2PdKvvmefGBoLA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=cYuZ/e0jXgUfq1EookmHyB6gBze4s1k3CAM7GBkKxv9edUZr/zWRbXtVhX6TsaI0O J1MWUskhwlA/NqFjSRx3qQVjwr7zgHL8Wl/Etu5yCh/lANEVZE66Dm0kzata1xRbiR Qek1u1NnMGosEXqec0wbN6MqSpiI1Sl+RRVDoPJ0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405272AbfIFTBN (ORCPT ); Fri, 6 Sep 2019 15:01:13 -0400 Received: from mga06.intel.com ([134.134.136.31]:16332 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405197AbfIFTBM (ORCPT ); Fri, 6 Sep 2019 15:01:12 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 06 Sep 2019 12:01:12 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,474,1559545200"; d="scan'208";a="190907127" Received: from unknown (HELO localhost.localdomain) ([10.232.112.69]) by FMSMGA003.fm.intel.com with ESMTP; 06 Sep 2019 12:01:11 -0700 Date: Fri, 6 Sep 2019 12:52:11 -0600 From: Keith Busch To: Sagi Grimberg Cc: Daniel Lezcano , Ming Lei , Jens Axboe , Hannes Reinecke , Bart Van Assche , linux-scsi@vger.kernel.org, Peter Zijlstra , Long Li , John Garry , LKML , linux-nvme@lists.infradead.org, Keith Busch , Ingo Molnar , Thomas Gleixner , Christoph Hellwig Subject: Re: [PATCH 1/4] softirq: implement IRQ flood detection mechanism Message-ID: <20190906185210.GA4260@localhost.localdomain> References: <6b88719c-782a-4a63-db9f-bf62734a7874@linaro.org> <20190903072848.GA22170@ming.t460p> <6f3b6557-1767-8c80-f786-1ea667179b39@acm.org> <2a8bd278-5384-d82f-c09b-4fce236d2d95@linaro.org> <20190905090617.GB4432@ming.t460p> <6a36ccc7-24cd-1d92-fef1-2c5e0f798c36@linaro.org> <20190906014819.GB27116@ming.t460p> <6eb2a745-7b92-73ce-46f5-cc6a5ef08abc@grimberg.me> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6eb2a745-7b92-73ce-46f5-cc6a5ef08abc@grimberg.me> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 06, 2019 at 11:30:57AM -0700, Sagi Grimberg wrote: > > > > > Ok, so the real problem is per-cpu bounded tasks. > > > > I share Thomas opinion about a NAPI like approach. > > We already have that, its irq_poll, but it seems that for this > use-case, we get lower performance for some reason. I'm not > entirely sure why that is, maybe its because we need to mask interrupts > because we don't have an "arm" register in nvme like network devices > have? For MSI, that's the INTMS/INTMC NVMe registers. MSI-x, though, has to disarm it in its table entry, and the Linux implementation will do a posted read in that path, which is a bit too expensive.