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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,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 A7008C43603 for ; Thu, 12 Dec 2019 09:14:17 +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 5B978214D8 for ; Thu, 12 Dec 2019 09:14:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="sJZUOCKe" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5B978214D8 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.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=pm+9VcTy6ZSZLCNGnCLJWGRAUHUIvydY4USGpvEphGo=; b=sJZUOCKe+xZNLg GGBT8TbI7ZdWCoEk5IU6NRoRIeE1gkqyVHFl3PXK8+lHpVWtrB06de974UPzjPeHiFGJOKeHZreaA CTbLkCzu5QY+gizTGeZtZA4GNILSHTJCcd5LniiIDCNA/r74PjWaWO8Rx+TZjrlfC4OzV/YdF+EE6 MDMzb3QA6huuOmsfB7E11YaLLRwKiAcxDNmC53iAB5NEwDTqhMTNR5eCYPB9Pz6xMRf2zeiFo0X83 Ws8fxMtLJmVgYx0dk5xFKEuxaPPW6n/fWjrUpDOcBLTooSDC0HDJY8WQVlTA76jnUHScgSAOItfZH NlGBpwOqOXgrSHqhvT8Q==; 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 1ifKY3-00063l-43; Thu, 12 Dec 2019 09:14:15 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1ifKY0-00063M-0n for linux-nvme@lists.infradead.org; Thu, 12 Dec 2019 09:14:13 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 3BCA268B05; Thu, 12 Dec 2019 10:14:09 +0100 (CET) Date: Thu, 12 Dec 2019 10:14:09 +0100 From: Christoph Hellwig To: Keith Busch Subject: Re: [PATCHv3 2/4] nvme/pci: Complete commands from primary handler Message-ID: <20191212091408.GC2399@lst.de> References: <20191209175622.1964-1-kbusch@kernel.org> <20191209175622.1964-3-kbusch@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20191209175622.1964-3-kbusch@kernel.org> User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191212_011412_207948_91B9281D X-CRM114-Status: GOOD ( 15.54 ) 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: sagi@grimberg.me, bigeasy@linutronix.de, linux-nvme@lists.infradead.org, ming.lei@redhat.com, tglx@linutronix.de, hch@lst.de 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 Tue, Dec 10, 2019 at 02:56:20AM +0900, Keith Busch wrote: > The context switch to wake the threaded interrupt handler has enough > overhead to harm latency for low queue depth workloads. Complete one cycle > through the completion queue in the primary handler to ensure threaded > interrupts have no disadvantage compared to not using threaded interrupts. Wake > the thread only if more completions remain after processing the queue > once since that indicates a higher queue depth workload that may trigger > frequent interrupts which would be better completed in the handler thread > with device interrupts disabled. > > Completing requests from two different contexts is safe since nvme driver > disables entry to the primary handler when it returns IRQ_WAKE_THREAD. > > Signed-off-by: Keith Busch > --- > drivers/nvme/host/pci.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c > index a0138e3ca0b9..e415fadf7331 100644 > --- a/drivers/nvme/host/pci.c > +++ b/drivers/nvme/host/pci.c > @@ -1055,6 +1055,10 @@ static irqreturn_t nvme_irq_check(int irq, void *data) > if (!nvme_cqe_pending(nvmeq)) > return IRQ_NONE; > > + nvme_irq(irq, data); I think we can just open code nvme_irq here. That also means we can use the return value of nvme_process_cq instead of the extra nvme_cqe_pending check above. This also needs a good comment explaining the scheme at least. > + if (!nvme_cqe_pending(nvmeq)) > + return IRQ_HANDLED; Including one explaining this check. _______________________________________________ linux-nvme mailing list linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme