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xen/blkfront: negotiate number of queues/rings to be used with backend

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The max number of hardware queues for xen/blkfront is set by parameter
'max_queues'(default 4), while 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 needs to read this negotiated number.

Signed-off-by: Bob Liu <bob.liu@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Bob Liu 2015-11-14 11:12:14 +08:00 committed by Konrad Rzeszutek Wilk
parent 11659569f7
commit 28d949bcc2
1 changed files with 120 additions and 42 deletions
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162
drivers/block/xen-blkfront.c
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@ -99,6 +99,10 @@ 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.
@ -118,6 +122,10 @@ 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)
/*
* queue-%u would take 7 + 10(UINT_MAX) = 17 characters.
*/
#define QUEUE_NAME_LEN (17)
/*
* Per-ring info.
@ -823,7 +831,7 @@ 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;
@ -1522,6 +1530,53 @@ fail:
return err;
}
/*
* Write out per-ring/queue nodes including ring-ref and event-channel, and each
* ring buffer may have multi pages depending on ->nr_ring_pages.
*/
static int write_per_ring_nodes(struct xenbus_transaction xbt,
struct blkfront_ring_info *rinfo, const char *dir)
{
int err;
unsigned int i;
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;
}
} 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;
}
}
}
err = xenbus_printf(xbt, dir, "event-channel", "%u", rinfo->evtchn);
if (err) {
message = "writing event-channel";
goto abort_transaction;
}
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,
@ -1529,10 +1584,9 @@ static int talk_to_blkback(struct xenbus_device *dev,
{
const char *message = NULL;
struct xenbus_transaction xbt;
int err, i;
unsigned int max_page_order = 0;
int err;
unsigned int i, 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);
@ -1544,7 +1598,8 @@ 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)
@ -1558,44 +1613,49 @@ 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;
}
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, 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);
if (info->nr_ring_pages > 1) {
err = xenbus_printf(xbt, dev->nodename, "ring-page-order", "%u",
ring_page_order);
if (err) {
message = "writing event-channel";
message = "writing ring-page-order";
goto abort_transaction;
}
}
/* 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 {
/* Not supported at this stage. */
goto abort_transaction;
char *path;
size_t pathsize;
err = xenbus_printf(xbt, dev->nodename, "multi-queue-num-queues", "%u",
info->nr_rings);
if (err) {
message = "writing multi-queue-num-queues";
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++) {
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);
}
err = xenbus_printf(xbt, dev->nodename, "protocol", "%s",
XEN_IO_PROTO_ABI_NATIVE);
@ -1619,8 +1679,7 @@ again:
for (i = 0; i < info->nr_rings; i++) {
unsigned int j;
rinfo = &info->rinfo[i];
struct blkfront_ring_info *rinfo = &info->rinfo[i];
for (j = 0; j < BLK_RING_SIZE(info); j++)
rinfo->shadow[j].req.u.rw.id = j + 1;
@ -1652,6 +1711,7 @@ static int blkfront_probe(struct xenbus_device *dev,
int err, vdevice;
unsigned int r_index;
struct blkfront_info *info;
unsigned int backend_max_queues = 0;
/* FIXME: Use dynamic device id if this is not set. */
err = xenbus_scanf(XBT_NIL, dev->nodename,
@ -1701,7 +1761,18 @@ static int blkfront_probe(struct xenbus_device *dev,
return -ENOMEM;
}
info->nr_rings = 1;
info->xbdev = dev;
/* Check if backend supports multiple queues. */
err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
"multi-queue-max-queues", "%u", &backend_max_queues);
if (err < 0)
backend_max_queues = 1;
info->nr_rings = min(backend_max_queues, xen_blkif_max_queues);
/* We need at least one ring. */
if (!info->nr_rings)
info->nr_rings = 1;
info->rinfo = kzalloc(sizeof(struct blkfront_ring_info) * info->nr_rings, GFP_KERNEL);
if (!info->rinfo) {
xenbus_dev_fatal(dev, -ENOMEM, "allocating ring_info structure");
@ -2390,6 +2461,7 @@ static struct xenbus_driver blkfront_driver = {
static int __init xlblk_init(void)
{
int ret;
int nr_cpus = num_online_cpus();
if (!xen_domain())
return -ENODEV;
@ -2400,6 +2472,12 @@ static int __init xlblk_init(void)
xen_blkif_max_ring_order = 0;
}
if (xen_blkif_max_queues > nr_cpus) {
pr_info("Invalid max_queues (%d), will use default max: %d.\n",
xen_blkif_max_queues, nr_cpus);
xen_blkif_max_queues = nr_cpus;
}
if (!xen_has_pv_disk_devices())
return -ENODEV;