From mboxrd@z Thu Jan 1 00:00:00 1970 From: Or Gerlitz Subject: Re: [PATCH V5 3/5] RDMA/iser: Limit sg tablesize and max_sectors to device fastreg max depth Date: Tue, 7 Jul 2015 17:32:12 +0300 Message-ID: <559BE2EC.8030806@mellanox.com> References: <20150705174353.10042.39648.stgit@build2.ogc.int> <20150705174452.10042.44695.stgit@build2.ogc.int> <559A335A.90506@dev.mellanox.co.il> <001401d0b7f9$09c21b40$1d4651c0$@opengridcomputing.com> <559B712D.7020105@dev.mellanox.co.il> <000601d0b8bd$2aa599d0$7ff0cd70$@opengridcomputing.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <000601d0b8bd$2aa599d0$7ff0cd70$@opengridcomputing.com> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Steve Wise , 'Sagi Grimberg' Cc: dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, infinipath-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, roid-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org, linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, eli-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org, target-devel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-rdma@vger.kernel.org On 7/7/2015 4:59 PM, Steve Wise wrote: >>>>> > >>>diff --git a/drivers/infiniband/ulp/iser/iscsi_iser.c b/drivers/infiniband/ulp/iser/iscsi_iser.c >>>>> > >>>index 6a594aa..de8730d 100644 >>>>> > >>>--- a/drivers/infiniband/ulp/iser/iscsi_iser.c >>>>> > >>>+++ b/drivers/infiniband/ulp/iser/iscsi_iser.c >>>>> > >>>@@ -640,6 +640,15 @@ iscsi_iser_session_create(struct iscsi_endpoint *ep, >>>>> > >>> SHOST_DIX_GUARD_CRC); >>>>> > >>> } >>>>> > >>> >>>>> > >>>+ /* >>>>> > >>>+ * Limit the sg_tablesize and max_sectors based on the device >>>>> > >>>+ * max fastreg page list length. >>>>> > >>>+ */ >>>>> > >>>+ shost->sg_tablesize = min_t(unsigned short, shost->sg_tablesize, >>>>> > >>>+ ib_conn->device->dev_attr.max_fast_reg_page_list_len); >>>>> > >>>+ shost->max_sectors = min_t(unsigned int, >>>>> > >>>+ 1024, (shost->sg_tablesize * PAGE_SIZE) >> 9); >>>>> > >>>+ >>>> > >> >>>> > >>The min statement is meaningless for max_sectors - you do a min between >>>> > >>default sg_tablesize and frpl length - so the maximum sg_tablesize is >>>> > >>128 which is 1024 max_sectors. >>> > > >>> > >I'm not following. What if ib_conn->device->dev_attr.max_fast_reg_page_list_len is say, 32? >>> > >Then shost->sg_tablesize is set to 32, and max_sectors is set to (32*4K) >> 9 == 256 512B sectors. >> > >> >Correct - but it cannot exceed 1024 (as it is derived from sg_tablesize >> >which is maximum 128). > Actually it is initialized to 1024 in iscsi_iser_sht / iscsi_iser.c, so it isn't derived from sg_tables (although it probably should be). I can remove the min_t() though. > > Hey Or, thoughts? Originally, we've put the double restriction of 128 SG entries AND 1024 sectors to make sure that whatever SG is up there, it'snot spanning > 512KB. Think on SG whose one/some of their element/s is > one page or on systems with > 4KB page size or others examples... since your patch touched the number of SG entries I was thinking you need to make sure no regression was introduced re the max_sectors to be <= 1024 If U2 are @ consensus that this is the case with the original patch w.o further changes, let it be. Or. -- 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