From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [PATCH rdma-core 1/5] util: Add common mmio macros Date: Tue, 18 Apr 2017 12:17:36 -0600 Message-ID: <20170418181736.GF7181@obsidianresearch.com> References: <1492123127-6266-1-git-send-email-jgunthorpe@obsidianresearch.com> <1492123127-6266-2-git-send-email-jgunthorpe@obsidianresearch.com> <20170418172852.GD7181@obsidianresearch.com> <20170418173815.GC14088@mtr-leonro.local> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20170418173815.GC14088-U/DQcQFIOTAAJjI8aNfphQ@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Leon Romanovsky Cc: Yishai Hadas , linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, "yishaih-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org" , Majd Dibbiny List-Id: linux-rdma@vger.kernel.org On Tue, Apr 18, 2017 at 08:38:15PM +0300, Leon Romanovsky wrote: > On Tue, Apr 18, 2017 at 11:28:52AM -0600, Jason Gunthorpe wrote: > > On Tue, Apr 18, 2017 at 06:52:00PM +0300, Yishai Hadas wrote: > > > > We could use a hash scheme or something to multiple the lock, but I'm > > really not sure that 32 bit performance matters to anyone anymore? > > In a hard way, I learned that we have a customer who expects that his 32bit > application will continue to work, so the answer is - no, I care. Of course it continues to work. Does your customer fit this very narrow definition: - Would actually upgrade to rdma-core - 32 bit - No SSE hardware (any Intel chip capable of PCI-E has SSE hardware) - Multiple same-provider devices with a single program touching all devices (single device performance is unchanged) - Sensitive to the performance difference of a potential spinlock contention / cache misplacement for ~4 instructions It is hard to understand who cares so much about peformance but leaves a wack on the table by running in 32 bit mode. Is this something like x32? We can certainly improve for x32. PPC32 could also potentially have a path like SSE.. 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