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=-5.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 93E77C432C0 for ; Mon, 2 Dec 2019 01:11:00 +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 5B32F2071F for ; Mon, 2 Dec 2019 01:11:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="SDvcFHsH"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="i/HbnkBF" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5B32F2071F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com 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=SPhBBYO4uMCYPSqsD4oj6Io20czSgrCUPyGmG7kn3Hk=; b=SDvcFHsHhOuIdi 2ABnOJ6qMzxRnI4L6POB8KDAYKHmKsft+dc6bDMtkMD1sf6SJsXq2gc+tQ4QKsEkQYtllH+zOLgqS n4xoQs3UpY87bzgWP2r4La5zh2hvY4P/1KKzkh/Oz8AG6VGH/ZOfTQd1ysMzSycExB5MnGb3vVmEe USnl0pCUI5WSD0wOwjcsNzo8uWg7H/MFIai50cy9RcWKODqU/w5A2x5ym/62CgD8HTvnEGjDmEPc9 LD1L7ltNCK1bRXyDT2fd8cYt028CSvFtVrIjaxjF10rjDiCrVMpem65jXIZx6+EMouMmS2rBG+cac gdB1dfhgB0G04M0dXIPQ==; 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 1ibaEp-0003YE-NU; Mon, 02 Dec 2019 01:10:55 +0000 Received: from us-smtp-2.mimecast.com ([207.211.31.81] helo=us-smtp-delivery-1.mimecast.com) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1ibaEl-0003Xm-Ej for linux-nvme@lists.infradead.org; Mon, 02 Dec 2019 01:10:53 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1575249048; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=B/3jdNKtgIJGaHYrF9YyqNgdrQ0yqo5F7IH0xMOLal0=; b=i/HbnkBFPX7OstCY2sWhUS+H6NV9MD/dpTy77PKU4bejUtnZg4XiVniIR3bR2zKiyKaUkf eRK8+hSCffNVP1ZRVpaZe3uxrhNwJcLc3CHtHDSm3Dyo2LTX91dCNiKy2XfBQJj0IxkAgQ MMZGmzXXVABWmg+GwZW7Rl2Xz0r/og8= 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-151-1HOGvMubM-2wUOqyeDMTrw-1; Sun, 01 Dec 2019 20:10:44 -0500 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 68457911E8; Mon, 2 Dec 2019 01:10:42 +0000 (UTC) Received: from ming.t460p (ovpn-8-21.pek2.redhat.com [10.72.8.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 634AE60BF7; Mon, 2 Dec 2019 01:10:35 +0000 (UTC) Date: Mon, 2 Dec 2019 09:10:31 +0800 From: Ming Lei To: Keith Busch Subject: Re: [PATCH 4/4] nvme/pci: Spin threaded interrupt completions Message-ID: <20191202011031.GA24512@ming.t460p> References: <20191127175824.1929-1-kbusch@kernel.org> <20191127175824.1929-5-kbusch@kernel.org> <20191129091302.bngxlcsbexiktqbk@linutronix.de> <20191130181020.GB5273@redsun51.ssa.fujisawa.hgst.com> MIME-Version: 1.0 In-Reply-To: <20191130181020.GB5273@redsun51.ssa.fujisawa.hgst.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-MC-Unique: 1HOGvMubM-2wUOqyeDMTrw-1 X-Mimecast-Spam-Score: 0 Content-Disposition: inline X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191201_171051_764633_2782F2CE X-CRM114-Status: GOOD ( 13.48 ) 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: Sebastian Andrzej Siewior , 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 Sun, Dec 01, 2019 at 03:10:20AM +0900, Keith Busch wrote: > On Fri, Nov 29, 2019 at 10:13:02AM +0100, Sebastian Andrzej Siewior wrote: > > On 2019-11-28 02:58:24 [+0900], Keith Busch wrote: > > > diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c > > > index 571b33b69c5f..9ec0933eb120 100644 > > > --- a/drivers/nvme/host/pci.c > > > +++ b/drivers/nvme/host/pci.c > > > @@ -1042,9 +1042,15 @@ static irqreturn_t nvme_irq(int irq, void *data) > > > return ret; > > > } > > > > > > +static void nvme_irq_spin(int irq, void *data) > > > +{ > > > + while (nvme_irq(irq, data) != IRQ_NONE) > > > + cond_resched(); > > > +} > > > > That interrupt thread runs at SCHED_FIFO prio 50 by default. You will > > not get anything with a lower priority running (including SCHED_OTHER). > > You won't get preempted by another FIFO thread at prio 50 so I *think* > > that cond_rechsched() won't let you schedule another task/IRQ thread > > running at prio 50 either. > > Hm, if we're really spinning here, the current alternative is that > we'd run a cpu 100% in irq context, which has its own problems. If the > interrupt thread has other scheduler issues, I think that indicates > yet another task needs to handle completions. Perhaps escalate to the > irq_poll solution Sagi advocated for if the threaded handler observes > need_resched() is true. Even without this issue, threaded irq has other issue, such as, IO latency is increased obviously. Thanks, Ming _______________________________________________ linux-nvme mailing list linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme