From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Van Assche Subject: Re: [PATCH for-3.11 7/7] IB/iser: Introduce fast memory registration model (FRWR) Date: Fri, 26 Jul 2013 11:27:05 +0200 Message-ID: <51F240E9.5000600@acm.org> References: <1374153931-7313-1-git-send-email-ogerlitz@mellanox.com> <1374153931-7313-8-git-send-email-ogerlitz@mellanox.com> <51ED1B8E.7070703@acm.org> <51ED2F97.2080400@mellanox.com> <51EE6FFE.8040802@acm.org> <51EE9773.9050003@acm.org> <51F000CB.3050808@mellanox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <51F000CB.3050808-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Or Gerlitz Cc: Sagi Grimberg , roland-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, roid-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org, oren-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org List-Id: linux-rdma@vger.kernel.org On 07/24/13 18:28, Or Gerlitz wrote: > On 23/07/2013 17:47, Bart Van Assche wrote: >> Still regarding page sizes: shouldn't ib_alloc_fast_reg_page_list() >> and ib_alloc_fast_reg_mr() multiply the SG list length by PAGE_SIZE / >> SIZE_4K to compensate for page size differences on architectures where >> virtual memory pages are larger than 4KB ? > > My understanding of the API is that it assumes that the HW is capable to > change the page shift (size) associated with certain fast_reg MR for > each mapping. I think you have a point here. Although I'm not sure this is what you had in mind, using PAGE_SIZE / PAGE_SHIFT instead of SIZE_4K / SHIFT_4K should work better on architectures with a page size larger than 4KB. On mlx4 the largest supported page list length is 511 (MLX4_MAX_FAST_REG_PAGES). So the former option should allow to support larger sg lists on such architectures (up to length 511) compared to the latter (up to length 511/(64/4) = 31 for 64KB pages). Bart. -- 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