From mboxrd@z Thu Jan 1 00:00:00 1970 From: jgunthorpe@obsidianresearch.com (Jason Gunthorpe) Date: Wed, 3 May 2017 09:53:16 -0600 Subject: [PATCH v4, under testing] nvme-rdma: support devices with queue size < 32 In-Reply-To: <780938034.8003164.1493824767084.JavaMail.zimbra@kalray.eu> References: <79901165.5342369.1493805915415.JavaMail.zimbra@kalray.eu> <823aa3f0-685f-4569-11d6-238cc4f0b126@grimberg.me> <780938034.8003164.1493824767084.JavaMail.zimbra@kalray.eu> Message-ID: <20170503155316.GA14334@obsidianresearch.com> On Wed, May 03, 2017@05:19:27PM +0200, Marta Rybczynska wrote: > > where > > queue->sig_limit = max(queue->queue_size / 2, 1); > > I tried to avoid that because this adds a division in the fast path Bart > was unhappy about in v2. The compiler switches divide/multiply by powers of two into fast bit shifts. Jason From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [PATCH v4, under testing] nvme-rdma: support devices with queue size < 32 Date: Wed, 3 May 2017 09:53:16 -0600 Message-ID: <20170503155316.GA14334@obsidianresearch.com> References: <79901165.5342369.1493805915415.JavaMail.zimbra@kalray.eu> <823aa3f0-685f-4569-11d6-238cc4f0b126@grimberg.me> <780938034.8003164.1493824767084.JavaMail.zimbra@kalray.eu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <780938034.8003164.1493824767084.JavaMail.zimbra-FNhOzJFKnXGHXe+LvDLADg@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Marta Rybczynska Cc: Sagi Grimberg , linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-nvme-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Leon Romanovsky , axboe-b10kYP2dOMg@public.gmane.org, Max Gurtovoy , Christoph Hellwig , Keith Busch , Doug Ledford , Bart Van Assche , samuel jones List-Id: linux-rdma@vger.kernel.org On Wed, May 03, 2017 at 05:19:27PM +0200, Marta Rybczynska wrote: > > where > > queue->sig_limit = max(queue->queue_size / 2, 1); > > I tried to avoid that because this adds a division in the fast path Bart > was unhappy about in v2. The compiler switches divide/multiply by powers of two into fast bit shifts. Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html