From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga17.intel.com ([192.55.52.151]:19365 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388284AbeKFX7V (ORCPT ); Tue, 6 Nov 2018 18:59:21 -0500 Date: Tue, 6 Nov 2018 07:31:43 -0700 From: Keith Busch To: Johannes Thumshirn Cc: Jens Axboe , Linux Block Layer Mailinglist , Hannes Reinecke , Linux Kernel Mailinglist , Jan Kara , Sagi Grimberg Subject: Re: [PATCH] block: respect virtual boundary mask in bvecs Message-ID: <20181106143143.GA5977@localhost.localdomain> References: <20181105102301.9752-1-jthumshirn@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20181105102301.9752-1-jthumshirn@suse.de> Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org On Mon, Nov 05, 2018 at 11:23:01AM +0100, Johannes Thumshirn wrote: > With drivers like iSer we are seeing a lot of bio splitting and smaller I/Os > being submitted to the driver. > > The root cause of this issue that the virtual boundary mask code does not take > into consideration that some of the memory segments in the SG list may have > come from a huge memory page that is being managed in the SG list as 4K > blocks. This means that many of the segments in the SG list will have an > offset into the page that is not 0 but will be a multiple of 4K. I probably got this wrong, but I thought a 2M huge page was 512 regular pages with a compound head, and offsets were from those regular pages rather than from the head. Overall though, the patch makes sense to me for this and other reasons. Acked-by: Keith Busch > Cc: Jan Kara > Cc: Sagi Grimberg > Signed-off-by: Johannes Thumshirn > --- > block/blk-merge.c | 2 +- > block/blk.h | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/block/blk-merge.c b/block/blk-merge.c > index 6b5ad275ed56..208658a901c6 100644 > --- a/block/blk-merge.c > +++ b/block/blk-merge.c > @@ -46,7 +46,7 @@ static inline bool bio_will_gap(struct request_queue *q, > bio_get_first_bvec(prev_rq->bio, &pb); > else > bio_get_first_bvec(prev, &pb); > - if (pb.bv_offset) > + if (pb.bv_offset & queue_virt_boundary(q)) > return true; > > /* > diff --git a/block/blk.h b/block/blk.h > index a1841b8ff129..c85e53f21cdd 100644 > --- a/block/blk.h > +++ b/block/blk.h > @@ -169,7 +169,7 @@ static inline bool biovec_phys_mergeable(struct request_queue *q, > static inline bool __bvec_gap_to_prev(struct request_queue *q, > struct bio_vec *bprv, unsigned int offset) > { > - return offset || > + return (offset & queue_virt_boundary(q)) || > ((bprv->bv_offset + bprv->bv_len) & queue_virt_boundary(q)); > } > > --