Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965188AbbKDBLZ (ORCPT ); Tue, 3 Nov 2015 20:11:25 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:21551 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965032AbbKDBLY (ORCPT ); Tue, 3 Nov 2015 20:11:24 -0500 Message-ID: <56395B2E.7030301@oracle.com> Date: Wed, 04 Nov 2015 09:11:10 +0800 From: Bob Liu User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130308 Thunderbird/17.0.4 MIME-Version: 1.0 To: Konrad Rzeszutek Wilk 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 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> In-Reply-To: <20151103204029.GH28527@char.us.oracle.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Source-IP: aserv0022.oracle.com [141.146.126.234] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8204 Lines: 257 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. >> + 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/