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=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 97AC1C432C0 for ; Tue, 3 Dec 2019 07:42:09 +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 6B33420637 for ; Tue, 3 Dec 2019 07:42:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="aF1zkNy7" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6B33420637 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=PU0CRy/mS7D97IgDsnJz0GalKnwN9HgKLFwG40RclxA=; b=aF1zkNy790fsPh JqlKAvthaRZ09lfynWGGjXaFU0jS00gZw62ZdCxpj9Ly2xMvkKhDtAdy3DDgCIqycTavPgvLamoHW GkrGkhvPzVtp7AZDZgEwJEnF7rs9n02y3CKVIv3z5H2Jg6XO9Z9Fw9Jhqawt9RCmZR5GJHbsaGSky whmaV/VfTGuHsjlHLvqOmiU7OPNGlHuBHXA835U2R4TulKBxK4GtvpwfMPjvhsHNgHJB0qB9qoYgI 4T1oIEQ3PhWH651V7bT04R6W8QAcM1fsKeA6i8/h9N1KxpokEudFJ6ako4NTxbSrHJid+bla438n0 7aGftW83Y4cRiMZ9aKaQ==; 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 1ic2ox-0005R8-IP; Tue, 03 Dec 2019 07:42:07 +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 1ic2ou-0005QV-Ld for linux-nvme@lists.infradead.org; Tue, 03 Dec 2019 07:42:05 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id C3B7F68BFE; Tue, 3 Dec 2019 08:42:02 +0100 (CET) Date: Tue, 3 Dec 2019 08:42:02 +0100 From: Christoph Hellwig To: Sebastian Andrzej Siewior Subject: Re: [PATCH 0/4] nvme: Threaded interrupt handling improvements Message-ID: <20191203074202.GD23881@lst.de> References: <20191127175824.1929-1-kbusch@kernel.org> <20191129094640.6fq6wcxmfi4fwnlw@linutronix.de> <20191129162719.GA47681@C02WT3WMHTD6.lpcnextlight.net> <20191129170545.axnykbrabigzcghs@linutronix.de> <20191130170222.GA5273@redsun51.ssa.fujisawa.hgst.com> <20191202170538.juq745vddzsouufb@linutronix.de> <20191202171239.GA8547@lst.de> <20191202195730.bzzldihtv37odsie@linutronix.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20191202195730.bzzldihtv37odsie@linutronix.de> 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-20191202_234204_851071_078F98EB X-CRM114-Status: GOOD ( 11.63 ) 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, linux-nvme@lists.infradead.org, ming.lei@redhat.com, helgaas@kernel.org, Keith Busch , tglx@linutronix.de, Christoph Hellwig 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 Mon, Dec 02, 2019 at 08:57:30PM +0100, Sebastian Andrzej Siewior wrote: > > The problem is that by doing the agressive polling we can keep one > > CPU busy just running the irq handler and starve processes on that > > CPU if an NVMe queue servers multiple CPUs. > > and this is bad? The scheduler will move everything to other CPUs unless > it is for pinned to this CPU. You can offload even RCU these days :) > Performance wise it might be better to dedicate one CPU doing this work > instead spreading it over four CPUs each doing a fraction of it and > using same cache lines which bounce from one CPU to the next. Ok, maybe things are getting better these days. I remember we did need the QUEUE_FLAG_SAME_FORCE flag back in the day to ensure I/O submitters are properly throttled by the completions they receive. _______________________________________________ linux-nvme mailing list linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme