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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 DB2DEC432C0 for ; Fri, 29 Nov 2019 17:05:57 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 95B2D215A5 for ; Fri, 29 Nov 2019 17:05:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="k2ALX5Qz" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 95B2D215A5 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=261lFO+ke3QvWQMWHRbn4DYYhTdUjhqkSHZapNvRd5U=; b=k2ALX5QzWp1qsp YryfRWN69nXwP+ZNpOucVLLEau/tmKaf5HoYqmQQP6C68cG1Ovw8jx7MO07RjncKGYDWVSFYoLM8y l7lYeVDyZu9b3gcwLhj9XxfRC57cj4XI/7C4ymqB4T3NL/DgmFMYA8e3e0W526t9UI6F/ShIQE8W1 VsVj5LplGUevXeTFhQ20FvAhk+40FRI60AHVO69f5J1QTj3ULD3CORwOXSA1v1pSlLAWJ8e3cdBz2 GdZPA7mZaeM58oBT6ovukiwwl34G56MiuHRnPEV7owCobTyeBvIljd/HrJJukAzriN7wKEwV+FoPe JYrLOegCunvqMWPjM8fg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iajiM-00062y-Ry; Fri, 29 Nov 2019 17:05:54 +0000 Received: from galois.linutronix.de ([2a0a:51c0:0:12e:550::1]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1iajiH-00061n-AG for linux-nvme@lists.infradead.org; Fri, 29 Nov 2019 17:05:53 +0000 Received: from bigeasy by Galois.linutronix.de with local (Exim 4.80) (envelope-from ) id 1iajiD-0002UP-SF; Fri, 29 Nov 2019 18:05:45 +0100 Date: Fri, 29 Nov 2019 18:05:45 +0100 From: Sebastian Andrzej Siewior To: Keith Busch Subject: Re: [PATCH 0/4] nvme: Threaded interrupt handling improvements Message-ID: <20191129170545.axnykbrabigzcghs@linutronix.de> References: <20191127175824.1929-1-kbusch@kernel.org> <20191129094640.6fq6wcxmfi4fwnlw@linutronix.de> <20191129162719.GA47681@C02WT3WMHTD6.lpcnextlight.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20191129162719.GA47681@C02WT3WMHTD6.lpcnextlight.net> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191129_090551_735801_4EFB2C2F X-CRM114-Status: GOOD ( 12.25 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: ming.lei@redhat.com, helgaas@kernel.org, hch@lst.de, linux-nvme@lists.infradead.org, sagi@grimberg.me Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 2019-11-29 09:27:19 [-0700], Keith Busch wrote: > On Fri, Nov 29, 2019 at 10:46:40AM +0100, Sebastian Andrzej Siewior wrote: > > On 2019-11-28 02:58:20 [+0900], Keith Busch wrote: > > > Threaded interrupts allow the device to continue sending interrupt > > > messages while the driver is handling the previous notification. This > > > can cause a significant amount of CPU cycles unnecessarily spent in hard > > > irq context, and potentially triggers spurious interrupt detection to > > > disable the nvme interrupt. > > > > Thank you for looking into this. > > To be clear: the "spurious interrupt detector" won't do a thing if you > > never return IRQ_NONE. As long as you return IRQ_HANDLED, everything is > > fine. > > That's not entirely accurate. We have to return IRQ_WAKE_THREAD > from the hardirq handler, which gets converted to IRQ_NONE if > desc->threads_handled hasn't changed and considered spurious. If > the threaded handler runs sufficiently long, desc->threads_handled > won't get updated frequently enough, so this series fixes that for > nvme by masking the interrupt in the device, preventing future hard > irq callbacks. Ach okay. But I wouldn't consider it as a "bug" if your threaded handler returns IRQ_HANDLED and requires a longer period of time. Thsi seems fine to me. The SDHCI driver has a case where the interrupt thread waits for another interrupt (from its primary handler) in order to make progress. Sebastian _______________________________________________ linux-nvme mailing list linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme