From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932800AbbKDByI (ORCPT ); Tue, 3 Nov 2015 20:54:08 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:33332 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752355AbbKDByG (ORCPT ); Tue, 3 Nov 2015 20:54:06 -0500 Date: Tue, 3 Nov 2015 20:53:43 -0500 From: Konrad Rzeszutek Wilk To: Bob Liu Cc: xen-devel@lists.xen.org, linux-kernel@vger.kernel.org, roger.pau@citrix.com, felipe.franciosi@citrix.com, axboe@fb.com, avanzini.arianna@gmail.com, rafal.mielniczuk@citrix.com, jonathan.davies@citrix.com, david.vrabel@citrix.com Subject: Re: [PATCH v4 05/10] xen/blkfront: negotiate number of queues/rings to be used with backend Message-ID: <20151104015342.GB3882@x230.dumpdata.com> References: <1446438106-20171-1-git-send-email-bob.liu@oracle.com> <1446438106-20171-6-git-send-email-bob.liu@oracle.com> <20151103204029.GH28527@char.us.oracle.com> <56395B2E.7030301@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56395B2E.7030301@oracle.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-Source-IP: aserv0021.oracle.com [141.146.126.233] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 04, 2015 at 09:11:10AM +0800, Bob Liu wrote: > > On 11/04/2015 04:40 AM, Konrad Rzeszutek Wilk wrote: > > On Mon, Nov 02, 2015 at 12:21:41PM +0800, Bob Liu wrote: > >> The number of hardware queues for xen/blkfront is set by parameter > >> 'max_queues'(default 4), while the max value xen/blkback supported is notified > >> through xenstore("multi-queue-max-queues"). > > > > That is not right. > > > > s/The number/The max number/ > > > > The second part: ",while the max value xen/blkback supported is..". I think > > you are trying to say: "it is also capped by the max value that > > the xen/blkback exposes through XenStore key 'multi-queue-max-queues'. > > > >> > >> The negotiated number is the smaller one and would be written back to xenstore > >> as "multi-queue-num-queues", blkback need to read this negotiated number. > > > > s/blkback need to read/blkback needs to read this/ > > > >> > >> Signed-off-by: Bob Liu > >> --- > >> drivers/block/xen-blkfront.c | 166 +++++++++++++++++++++++++++++++------------ > >> 1 file changed, 120 insertions(+), 46 deletions(-) > >> > >> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c > >> index 8cc5995..23096d7 100644 > >> --- a/drivers/block/xen-blkfront.c > >> +++ b/drivers/block/xen-blkfront.c > >> @@ -98,6 +98,10 @@ static unsigned int xen_blkif_max_segments = 32; > >> module_param_named(max, xen_blkif_max_segments, int, S_IRUGO); > >> MODULE_PARM_DESC(max, "Maximum amount of segments in indirect requests (default is 32)"); > >> > >> +static unsigned int xen_blkif_max_queues = 4; > >> +module_param_named(max_queues, xen_blkif_max_queues, uint, S_IRUGO); > >> +MODULE_PARM_DESC(max_queues, "Maximum number of hardware queues/rings used per virtual disk"); > >> + > >> /* > >> * Maximum order of pages to be used for the shared ring between front and > >> * backend, 4KB page granularity is used. > >> @@ -113,6 +117,7 @@ MODULE_PARM_DESC(max_ring_page_order, "Maximum order of pages to be used for the > >> * characters are enough. Define to 20 to keep consist with backend. > >> */ > >> #define RINGREF_NAME_LEN (20) > >> +#define QUEUE_NAME_LEN (12) > > > > Little bit of documentation please. Why 12? Why not 31415 for example? > > I presume it is 'queue-%u' and since so that is 7 + 10 (UINT_MAX is > > 4294967295) = 17! > > > > > >> > >> /* > >> * Per-ring info. > >> @@ -695,7 +700,7 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size, > >> > >> memset(&info->tag_set, 0, sizeof(info->tag_set)); > >> info->tag_set.ops = &blkfront_mq_ops; > >> - info->tag_set.nr_hw_queues = 1; > >> + info->tag_set.nr_hw_queues = info->nr_rings; > >> info->tag_set.queue_depth = BLK_RING_SIZE(info); > >> info->tag_set.numa_node = NUMA_NO_NODE; > >> info->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_SG_MERGE; > >> @@ -1352,6 +1357,51 @@ fail: > >> return err; > >> } > >> > >> +static int write_per_ring_nodes(struct xenbus_transaction xbt, > >> + struct blkfront_ring_info *rinfo, const char *dir) > >> +{ > >> + int err, i; > > > > Please make 'i' be an unsigned int. Especially as you are using '%u' in the snprintf. > > > > > >> + const char *message = NULL; > >> + struct blkfront_info *info = rinfo->dev_info; > >> + > >> + if (info->nr_ring_pages == 1) { > >> + err = xenbus_printf(xbt, dir, "ring-ref", "%u", rinfo->ring_ref[0]); > >> + if (err) { > >> + message = "writing ring-ref"; > >> + goto abort_transaction; > >> + } > >> + pr_info("%s: write ring-ref:%d\n", dir, rinfo->ring_ref[0]); > > > > Ewww. No. > > > >> + } else { > >> + for (i = 0; i < info->nr_ring_pages; i++) { > >> + char ring_ref_name[RINGREF_NAME_LEN]; > >> + > >> + snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i); > >> + err = xenbus_printf(xbt, dir, ring_ref_name, > >> + "%u", rinfo->ring_ref[i]); > >> + if (err) { > >> + message = "writing ring-ref"; > >> + goto abort_transaction; > >> + } > >> + pr_info("%s: write ring-ref:%d\n", dir, rinfo->ring_ref[i]); > > > > No no please. > > > >> + } > >> + } > >> + > >> + err = xenbus_printf(xbt, dir, "event-channel", "%u", rinfo->evtchn); > > > > That is not right. > > > > That only creates one. But the blkif.h says (And the example agrees) > > that there are N 'event-channel' for N-rings. > > > > Shouldn't this be part of the above loop? > > > > No, this loop is only for per-ring each with "multipage". > > The loop you want is.. > > >> + if (err) { > >> + message = "writing event-channel"; > >> + goto abort_transaction; > >> + } > >> + pr_info("%s: write event-channel:%d\n", dir, rinfo->evtchn); > > > > Please no. > > > >> + > >> + return 0; > >> + > >> +abort_transaction: > >> + xenbus_transaction_end(xbt, 1); > >> + if (message) > >> + xenbus_dev_fatal(info->xbdev, err, "%s", message); > >> + > >> + return err; > >> +} > >> > >> /* Common code used when first setting up, and when resuming. */ > >> static int talk_to_blkback(struct xenbus_device *dev, > >> @@ -1362,7 +1412,6 @@ static int talk_to_blkback(struct xenbus_device *dev, > >> int err, i; > >> unsigned int max_page_order = 0; > >> unsigned int ring_page_order = 0; > >> - struct blkfront_ring_info *rinfo; > >> > >> err = xenbus_scanf(XBT_NIL, info->xbdev->otherend, > >> "max-ring-page-order", "%u", &max_page_order); > >> @@ -1374,7 +1423,8 @@ static int talk_to_blkback(struct xenbus_device *dev, > >> } > >> > >> for (i = 0; i < info->nr_rings; i++) { > >> - rinfo = &info->rinfo[i]; > >> + struct blkfront_ring_info *rinfo = &info->rinfo[i]; > >> + > >> /* Create shared ring, alloc event channel. */ > >> err = setup_blkring(dev, rinfo); > >> if (err) > >> @@ -1388,45 +1438,51 @@ again: > >> goto destroy_blkring; > >> } > >> > >> - if (info->nr_rings == 1) { > >> - rinfo = &info->rinfo[0]; > >> - if (info->nr_ring_pages == 1) { > >> - err = xenbus_printf(xbt, dev->nodename, > >> - "ring-ref", "%u", rinfo->ring_ref[0]); > >> - if (err) { > >> - message = "writing ring-ref"; > >> - goto abort_transaction; > >> - } > >> - } else { > >> - err = xenbus_printf(xbt, dev->nodename, > >> - "ring-page-order", "%u", ring_page_order); > >> - if (err) { > >> - message = "writing ring-page-order"; > >> - goto abort_transaction; > >> - } > >> + if (info->nr_ring_pages > 1) { > >> + err = xenbus_printf(xbt, dev->nodename, "ring-page-order", "%u", > >> + ring_page_order); > >> + if (err) { > >> + message = "writing ring-page-order"; > >> + goto abort_transaction; > >> + } > >> + } > >> > >> - for (i = 0; i < info->nr_ring_pages; i++) { > >> - char ring_ref_name[RINGREF_NAME_LEN]; > >> + /* We already got the number of queues/rings in _probe */ > >> + if (info->nr_rings == 1) { > >> + err = write_per_ring_nodes(xbt, &info->rinfo[0], dev->nodename); > >> + if (err) > >> + goto destroy_blkring; > >> + } else { > >> + char *path; > >> + size_t pathsize; > >> > >> - snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i); > >> - err = xenbus_printf(xbt, dev->nodename, ring_ref_name, > >> - "%u", rinfo->ring_ref[i]); > >> - if (err) { > >> - message = "writing ring-ref"; > >> - goto abort_transaction; > >> - } > >> - } > >> - } > >> - err = xenbus_printf(xbt, dev->nodename, > >> - "event-channel", "%u", rinfo->evtchn); > >> + err = xenbus_printf(xbt, dev->nodename, "multi-queue-num-queues", "%u", > >> + info->nr_rings); > >> if (err) { > >> - message = "writing event-channel"; > >> + message = "writing multi-queue-num-queues"; > >> goto abort_transaction; > >> } > >> - } else { > >> - /* Not supported at this stage */ > >> - goto abort_transaction; > >> + > >> + pathsize = strlen(dev->nodename) + QUEUE_NAME_LEN; > >> + path = kmalloc(pathsize, GFP_KERNEL); > >> + if (!path) { > >> + err = -ENOMEM; > >> + message = "ENOMEM while writing ring references"; > >> + goto abort_transaction; > >> + } > >> + > >> + for (i = 0; i < info->nr_rings; i++) { > > at here. Please document that then. That is a bit confusing. > > >> + memset(path, 0, pathsize); > >> + snprintf(path, pathsize, "%s/queue-%u", dev->nodename, i); > >> + err = write_per_ring_nodes(xbt, &info->rinfo[i], path); > >> + if (err) { > >> + kfree(path); > >> + goto destroy_blkring; > >> + } > >> + } > >> + kfree(path); > >> } > >> + > > Will update all other comments. > > -- > Regards, > -Bob