From mboxrd@z Thu Jan 1 00:00:00 1970 From: juncheng bai Subject: Re: [PATCH RFC] storage:rbd: make the size of request is equal to the, size of the object Date: Mon, 15 Jun 2015 21:23:32 +0800 Message-ID: <557ED1D4.20605@unitedstack.com> References: <557EB47F.6090708@unitedstack.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from smtpproxy19.qq.com ([184.105.206.84]:33105 "EHLO smtpproxy19.qq.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754072AbbFONXu (ORCPT ); Mon, 15 Jun 2015 09:23:50 -0400 In-Reply-To: Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Ilya Dryomov Cc: idryomov@redhat.com, Alex Elder , Josh Durgin , lucienchao@gmail.com, jeff@garzik.org, yehuda@hq.newdream.net, Sage Weil , elder@inktank.com, "linux-kernel@vger.kernel.org" , Ceph Development On 2015/6/15 21:03, Ilya Dryomov wrote: > On Mon, Jun 15, 2015 at 2:18 PM, juncheng bai > wrote: >> From 6213215bd19926d1063d4e01a248107dab8a899b Mon Sep 17 00:00:00 2001 >> From: juncheng bai >> Date: Mon, 15 Jun 2015 18:34:00 +0800 >> Subject: [PATCH] storage:rbd: make the size of request is equal to the >> size of the object >> >> ensures that the merged size of request can achieve the size of >> the object. >> when merge a bio to request or merge a request to request, the >> sum of the segment number of the current request and the segment >> number of the bio is not greater than the max segments of the request, >> so the max size of request is 512k if the max segments of request is >> BLK_MAX_SEGMENTS. >> >> Signed-off-by: juncheng bai >> --- >> drivers/block/rbd.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c >> index 0a54c58..dec6045 100644 >> --- a/drivers/block/rbd.c >> +++ b/drivers/block/rbd.c >> @@ -3757,6 +3757,8 @@ static int rbd_init_disk(struct rbd_device *rbd_dev) >> segment_size = rbd_obj_bytes(&rbd_dev->header); >> blk_queue_max_hw_sectors(q, segment_size / SECTOR_SIZE); >> blk_queue_max_segment_size(q, segment_size); >> + if (segment_size > BLK_MAX_SEGMENTS * PAGE_SIZE) >> + blk_queue_max_segments(q, segment_size / PAGE_SIZE); >> blk_queue_io_min(q, segment_size); >> blk_queue_io_opt(q, segment_size); > > I made a similar patch on Friday, investigating blk-mq plugging issue > reported by Nick. My patch sets it to BIO_MAX_PAGES unconditionally - > AFAIU there is no point in setting to anything bigger since the bios > will be clipped to that number of vecs. Given that BIO_MAX_PAGES is > 256, this gives is 1M direct I/Os. Hi. For signal bio, the max number of bio_vec is BIO_MAX_PAGES, but a request can be merged from multiple bios. We can see the below function: ll_back_merge_fn, ll_front_merge_fn and etc. And I test in kernel 3.18 use this patch, and do: echo 4096 > /sys/block/rbd0/queue/max_sectors_kb We use systemtap to trace the request size, It is upto 4M. Thanks. --------- juncheng bai > > Thanks, > > Ilya > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >