RE: [Xen-devel] [PATCH 2/2] drivers: xen/block: add multi-page ring support
From: Felipe Franciosi
Date: Thu Feb 05 2015 - 12:51:33 EST
Hi Bob,
Can you elaborate on the environment where you measured such an improvement?
I'm particularly interested in:
What workload were you issuing? (e.g. 4K seq reads?)
What backend were you using? (e.g. null driver? what parameters? some specific disk/array?)
What was the host configuration for the test?
What was the VM configuration for the test?
Thanks,
Felipe
-----Original Message-----
From: xen-devel-bounces@xxxxxxxxxxxxx [mailto:xen-devel-bounces@xxxxxxxxxxxxx] On Behalf Of Bob Liu
Sent: 23 January 2015 10:15
To: xen-devel@xxxxxxxxxxxxx
Cc: Wei Liu; linux-kernel@xxxxxxxxxxxxxxx; Bob Liu; David Vrabel; boris.ostrovsky@xxxxxxxxxx; Roger Pau Monne
Subject: [Xen-devel] [PATCH 2/2] drivers: xen/block: add multi-page ring support
Extend xen/block to support multi-page ring.
* xen-blkback notify blkfront with feature-multi-ring-pages
* xen-blkfront write to xenstore about how many pages are used as the ring
If using 4 pages as the ring, inflight requests inscreased from 32 to 128 and IOPS improved nearly 400% on our system.
Signed-off-by: Bob Liu <bob.liu@xxxxxxxxxx>
---
drivers/block/xen-blkback/xenbus.c | 86 +++++++++++++++++++++++++--------
drivers/block/xen-blkfront.c | 94 ++++++++++++++++++++++++++----------
2 files changed, 133 insertions(+), 47 deletions(-)
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index cbd13c9..a5c9c62 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -193,8 +193,8 @@ fail:
return ERR_PTR(-ENOMEM);
}
-static int xen_blkif_map(struct xen_blkif *blkif, grant_ref_t gref,
- unsigned int evtchn)
+static int xen_blkif_map(struct xen_blkif *blkif, grant_ref_t *gref,
+ unsigned int nr_grefs, unsigned int evtchn)
{
int err;
@@ -202,7 +202,7 @@ static int xen_blkif_map(struct xen_blkif *blkif, grant_ref_t gref,
if (blkif->irq)
return 0;
- err = xenbus_map_ring_valloc(blkif->be->dev, &gref, 1,
+ err = xenbus_map_ring_valloc(blkif->be->dev, gref, nr_grefs,
&blkif->blk_ring);
if (err < 0)
return err;
@@ -212,21 +212,21 @@ static int xen_blkif_map(struct xen_blkif *blkif, grant_ref_t gref,
{
struct blkif_sring *sring;
sring = (struct blkif_sring *)blkif->blk_ring;
- BACK_RING_INIT(&blkif->blk_rings.native, sring, PAGE_SIZE);
+ BACK_RING_INIT(&blkif->blk_rings.native, sring, PAGE_SIZE *
+nr_grefs);
break;
}
case BLKIF_PROTOCOL_X86_32:
{
struct blkif_x86_32_sring *sring_x86_32;
sring_x86_32 = (struct blkif_x86_32_sring *)blkif->blk_ring;
- BACK_RING_INIT(&blkif->blk_rings.x86_32, sring_x86_32, PAGE_SIZE);
+ BACK_RING_INIT(&blkif->blk_rings.x86_32, sring_x86_32, PAGE_SIZE *
+nr_grefs);
break;
}
case BLKIF_PROTOCOL_X86_64:
{
struct blkif_x86_64_sring *sring_x86_64;
sring_x86_64 = (struct blkif_x86_64_sring *)blkif->blk_ring;
- BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64, PAGE_SIZE);
+ BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64, PAGE_SIZE *
+nr_grefs);
break;
}
default:
@@ -588,6 +588,13 @@ static int xen_blkbk_probe(struct xenbus_device *dev,
if (err)
goto fail;
+ err = xenbus_printf(XBT_NIL, dev->nodename,
+ "feature-multi-ring-pages", "%u", 1);
+ if (err) {
+ pr_debug("Error writing feature-multi-ring-pages\n");
+ goto fail;
+ }
+
err = xenbus_switch_state(dev, XenbusStateInitWait);
if (err)
goto fail;
@@ -852,23 +859,61 @@ again:
static int connect_ring(struct backend_info *be) {
struct xenbus_device *dev = be->dev;
- unsigned long ring_ref;
- unsigned int evtchn;
+ unsigned int ring_ref[XENBUS_MAX_RING_PAGES];
+ unsigned int evtchn, nr_grefs;
unsigned int pers_grants;
char protocol[64] = "";
int err;
DPRINTK("%s", dev->otherend);
-
- err = xenbus_gather(XBT_NIL, dev->otherend, "ring-ref", "%lu",
- &ring_ref, "event-channel", "%u", &evtchn, NULL);
- if (err) {
- xenbus_dev_fatal(dev, err,
- "reading %s/ring-ref and event-channel",
- dev->otherend);
+ err = xenbus_scanf(XBT_NIL, dev->otherend, "event-channel", "%u",
+ &evtchn);
+ if (err != 1) {
+ err = -EINVAL;
+ xenbus_dev_fatal(dev, err, "reading %s/event-channel",
+ dev->otherend);
return err;
}
+ err = xenbus_scanf(XBT_NIL, dev->otherend, "max-ring-pages", "%u",
+ &nr_grefs);
+ if (err != 1) {
+ err = xenbus_scanf(XBT_NIL, dev->otherend, "ring-ref",
+ "%u", &ring_ref[0]);
+ if (err != 1) {
+ err = -EINVAL;
+ xenbus_dev_fatal(dev, err, "reading %s/ring-ref",
+ dev->otherend);
+ return err;
+ }
+ nr_grefs = 1;
+ pr_debug("%s:using one-page ring with ref: %d\n",
+ dev->otherend, ring_ref[0]);
+ } else {
+ unsigned int i;
+
+ if (nr_grefs > XENBUS_MAX_RING_PAGES) {
+ err = -EINVAL;
+ xenbus_dev_fatal(dev, err,
+ "%s/ring-pages:%d too big", dev->otherend, nr_grefs);
+ return err;
+ }
+ for (i = 0; i < nr_grefs; i++) {
+ char ring_ref_name[15];
+ snprintf(ring_ref_name, sizeof(ring_ref_name),
+ "ring-ref%u", i);
+ err = xenbus_scanf(XBT_NIL, dev->otherend,
+ ring_ref_name, "%d", &ring_ref[i]);
+ if (err != 1) {
+ err = -EINVAL;
+ xenbus_dev_fatal(dev, err, "reading %s/%s",
+ dev->otherend, ring_ref_name);
+ return err;
+ }
+ pr_debug("blkback: ring-ref%u: %d\n", i, ring_ref[i]);
+ }
+ }
+
be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
"%63s", protocol, NULL);
@@ -893,15 +938,14 @@ static int connect_ring(struct backend_info *be)
be->blkif->vbd.feature_gnt_persistent = pers_grants;
be->blkif->vbd.overflow_max_grants = 0;
- pr_info(DRV_PFX "ring-ref %ld, event-channel %d, protocol %d (%s) %s\n",
- ring_ref, evtchn, be->blkif->blk_protocol, protocol,
- pers_grants ? "persistent grants" : "");
+ pr_info(DRV_PFX "ring-pages:%d, event-channel %d, protocol %d (%s) %s\n",
+ nr_grefs, evtchn, be->blkif->blk_protocol, protocol,
+ pers_grants ? "persistent grants" : "");
/* Map the shared frame, irq etc. */
- err = xen_blkif_map(be->blkif, ring_ref, evtchn);
+ err = xen_blkif_map(be->blkif, ring_ref, nr_grefs, evtchn);
if (err) {
- xenbus_dev_fatal(dev, err, "mapping ring-ref %lu port %u",
- ring_ref, evtchn);
+ xenbus_dev_fatal(dev, err, "mapping ring-ref port %u", evtchn);
return err;
}
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index 2fcf75d..dec9fe7 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -98,7 +98,12 @@ 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)");
-#define BLK_RING_SIZE __CONST_RING_SIZE(blkif, PAGE_SIZE)
+static unsigned int xen_blkif_max_ring_pages = 1;
+module_param_named(max_ring_pages, xen_blkif_max_ring_pages, int, 0);
+MODULE_PARM_DESC(max_ring_pages, "Maximum amount of pages to be used as
+the ring");
+
+#define BLK_RING_SIZE __CONST_RING_SIZE(blkif, PAGE_SIZE *
+info->nr_ring_pages) #define BLK_MAX_RING_SIZE __CONST_RING_SIZE(blkif,
+PAGE_SIZE * XENBUS_MAX_RING_PAGES)
/*
* We have one of these per vbd, whether ide, scsi or 'other'. They @@ -114,13 +119,14 @@ struct blkfront_info
int vdevice;
blkif_vdev_t handle;
enum blkif_state connected;
- int ring_ref;
+ int ring_ref[XENBUS_MAX_RING_PAGES];
+ int nr_ring_pages;
struct blkif_front_ring ring;
unsigned int evtchn, irq;
struct request_queue *rq;
struct work_struct work;
struct gnttab_free_callback callback;
- struct blk_shadow shadow[BLK_RING_SIZE];
+ struct blk_shadow shadow[BLK_MAX_RING_SIZE];
struct list_head grants;
struct list_head indirect_pages;
unsigned int persistent_gnts_c;
@@ -139,8 +145,6 @@ static unsigned int nr_minors; static unsigned long *minors; static DEFINE_SPINLOCK(minor_lock);
-#define MAXIMUM_OUTSTANDING_BLOCK_REQS \
- (BLKIF_MAX_SEGMENTS_PER_REQUEST * BLK_RING_SIZE)
#define GRANT_INVALID_REF 0
#define PARTS_PER_DISK 16
@@ -1033,12 +1037,15 @@ free_shadow:
flush_work(&info->work);
/* Free resources associated with old device channel. */
- if (info->ring_ref != GRANT_INVALID_REF) {
- gnttab_end_foreign_access(info->ring_ref, 0,
- (unsigned long)info->ring.sring);
- info->ring_ref = GRANT_INVALID_REF;
- info->ring.sring = NULL;
+ for (i = 0; i < info->nr_ring_pages; i++) {
+ if (info->ring_ref[i] != GRANT_INVALID_REF) {
+ gnttab_end_foreign_access(info->ring_ref[i], 0, 0);
+ info->ring_ref[i] = GRANT_INVALID_REF;
+ }
}
+ free_pages((unsigned long)info->ring.sring, get_order(info->nr_ring_pages * PAGE_SIZE));
+ info->ring.sring = NULL;
+
if (info->irq)
unbind_from_irqhandler(info->irq, info);
info->evtchn = info->irq = 0;
@@ -1245,26 +1252,30 @@ static int setup_blkring(struct xenbus_device *dev,
struct blkfront_info *info)
{
struct blkif_sring *sring;
- int err;
- grant_ref_t gref;
+ int err, i;
+ unsigned long ring_size = info->nr_ring_pages * PAGE_SIZE;
+ grant_ref_t gref[XENBUS_MAX_RING_PAGES];
- info->ring_ref = GRANT_INVALID_REF;
+ for (i = 0; i < XENBUS_MAX_RING_PAGES; i++)
+ info->ring_ref[i] = GRANT_INVALID_REF;
- sring = (struct blkif_sring *)__get_free_page(GFP_NOIO | __GFP_HIGH);
+ sring = (struct blkif_sring *)__get_free_pages(GFP_NOIO | __GFP_HIGH,
+ get_order(ring_size));
if (!sring) {
xenbus_dev_fatal(dev, -ENOMEM, "allocating shared ring");
return -ENOMEM;
}
SHARED_RING_INIT(sring);
- FRONT_RING_INIT(&info->ring, sring, PAGE_SIZE);
+ FRONT_RING_INIT(&info->ring, sring, ring_size);
- err = xenbus_grant_ring(dev, info->ring.sring, 1, &gref);
+ err = xenbus_grant_ring(dev, info->ring.sring, info->nr_ring_pages,
+gref);
if (err < 0) {
free_page((unsigned long)sring);
info->ring.sring = NULL;
goto fail;
}
- info->ring_ref = gref;
+ for (i = 0; i < info->nr_ring_pages; i++)
+ info->ring_ref[i] = gref[i];
err = xenbus_alloc_evtchn(dev, &info->evtchn);
if (err)
@@ -1292,7 +1303,14 @@ static int talk_to_blkback(struct xenbus_device *dev, {
const char *message = NULL;
struct xenbus_transaction xbt;
- int err;
+ int err, i, multi_ring_pages = 0;
+
+ err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
+ "feature-multi-ring-pages", "%u", &multi_ring_pages);
+ if (err != 1)
+ info->nr_ring_pages = 1;
+ else
+ info->nr_ring_pages = xen_blkif_max_ring_pages;
/* Create shared ring, alloc event channel. */
err = setup_blkring(dev, info);
@@ -1306,12 +1324,33 @@ again:
goto destroy_blkring;
}
- err = xenbus_printf(xbt, dev->nodename,
- "ring-ref", "%u", info->ring_ref);
- if (err) {
- message = "writing ring-ref";
- goto abort_transaction;
+ if (info->nr_ring_pages == 1) {
+ err = xenbus_printf(xbt, dev->nodename,
+ "ring-ref", "%u", info->ring_ref[0]);
+ if (err) {
+ message = "writing ring-ref";
+ goto abort_transaction;
+ }
+ } else {
+ err = xenbus_printf(xbt, dev->nodename,
+ "max-ring-pages", "%u", info->nr_ring_pages);
+ if (err) {
+ message = "writing max-ring-pages";
+ goto abort_transaction;
+ }
+
+ for (i = 0; i < info->nr_ring_pages; i++) {
+ char ring_ref_name[15];
+ sprintf(ring_ref_name, "ring-ref%d", i);
+ err = xenbus_printf(xbt, dev->nodename,
+ ring_ref_name, "%d", info->ring_ref[i]);
+ if (err) {
+ message = "writing ring-ref";
+ goto abort_transaction;
+ }
+ }
}
+
err = xenbus_printf(xbt, dev->nodename,
"event-channel", "%u", info->evtchn);
if (err) {
@@ -1422,9 +1461,8 @@ static int blkfront_probe(struct xenbus_device *dev,
info->connected = BLKIF_STATE_DISCONNECTED;
INIT_WORK(&info->work, blkif_restart_queue);
- for (i = 0; i < BLK_RING_SIZE; i++)
+ for (i = 0; i < BLK_MAX_RING_SIZE; i++)
info->shadow[i].req.u.rw.id = i+1;
- info->shadow[BLK_RING_SIZE-1].req.u.rw.id = 0x0fffffff;
/* Front end dir is a number, which is used as the id. */
info->handle = simple_strtoul(strrchr(dev->nodename, '/')+1, NULL, 0); @@ -1436,6 +1474,7 @@ static int blkfront_probe(struct xenbus_device *dev,
dev_set_drvdata(&dev->dev, NULL);
return err;
}
+ info->shadow[BLK_RING_SIZE-1].req.u.rw.id = 0x0fffffff;
return 0;
}
@@ -1476,7 +1515,7 @@ static int blkif_recover(struct blkfront_info *info)
/* Stage 2: Set up free list. */
memset(&info->shadow, 0, sizeof(info->shadow));
- for (i = 0; i < BLK_RING_SIZE; i++)
+ for (i = 0; i < BLK_MAX_RING_SIZE; i++)
info->shadow[i].req.u.rw.id = i+1;
info->shadow_free = info->ring.req_prod_pvt;
info->shadow[BLK_RING_SIZE-1].req.u.rw.id = 0x0fffffff; @@ -2088,6 +2127,9 @@ static int __init xlblk_init(void) {
int ret;
+ if (xen_blkif_max_ring_pages > XENBUS_MAX_RING_PAGES)
+ return -EINVAL;
+
if (!xen_domain())
return -ENODEV;
--
1.7.10.4
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/