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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v2 2/2] xen/block: add multi-page ring support
On 03/31/2015 08:15 PM, Bob Liu wrote:
> Extend xen/block to support multi-page ring, so that more requests can be
> issued
> by using more than one pages as the request ring between blkfront and backend.
> As a result, the performance can get improved significantly.
>
> We got some impressive improvements on our highend iscsi storage cluster
> backend.
> If using 64 pages as the ring, the IOPS increased about 15 times for the
> throughput testing and above doubled for the latency testing.
>
> The reason was the limit on outstanding requests is 32 if use only one-page
> ring, but in our case the iscsi lun was spread across about 100 physical
> drives,
> 32 was really not enough to keep them busy.
>
> Change in V2:
> * Rebased to 4.0-rc6
> * Add description on how this protocol works into io/blkif.h
>
I found there were already some related descriptions in file
xen/include/public/io/blkif.h. I'll send an new patch following the
protocol in that file, and leave file include/xen/interface/io/blkif.h
unchanged.
190 * max-ring-pages
191 * Values: <uint32_t>
192 * Default Value: 1
193 * Notes: DEPRECATED, 2, 3
194 *
195 * The maximum supported size of the request ring buffer in
units of
196 * machine pages. The value must be a power of 2.
302 * num-ring-pages
303 * Values: <uint32_t>
304 * Default Value: 1
305 * Maximum Value: MAX(max-ring-pages,(0x1 << max-ring-page-order))
306 * Notes: DEPRECATED, 2, 3
307 *
308 * The size of the frontend allocated request ring buffer in
units of
309 * machine pages. The value must be a power of 2.
310 *
Regards,
-Bob
> Signed-off-by: Bob Liu <bob.liu@xxxxxxxxxx>
> ---
> drivers/block/xen-blkback/blkback.c | 2 +-
> drivers/block/xen-blkback/common.h | 3 +-
> drivers/block/xen-blkback/xenbus.c | 83 ++++++++++++++++++++-------
> drivers/block/xen-blkfront.c | 111
> +++++++++++++++++++++++++-----------
> include/xen/interface/io/blkif.h | 13 +++++
> 5 files changed, 156 insertions(+), 56 deletions(-)
>
> diff --git a/drivers/block/xen-blkback/blkback.c
> b/drivers/block/xen-blkback/blkback.c
> index 0c8da82..072d15b 100644
> --- a/drivers/block/xen-blkback/blkback.c
> +++ b/drivers/block/xen-blkback/blkback.c
> @@ -628,7 +628,7 @@ purge_gnt_list:
> }
>
> /* Shrink if we have more than xen_blkif_max_buffer_pages */
> - shrink_free_pagepool(blkif, xen_blkif_max_buffer_pages);
> + shrink_free_pagepool(blkif, xen_blkif_max_buffer_pages *
> blkif->nr_ring_pages);
>
> if (log_stats && time_after(jiffies, blkif->st_print))
> print_stats(blkif);
> diff --git a/drivers/block/xen-blkback/common.h
> b/drivers/block/xen-blkback/common.h
> index 375d288..320ca35 100644
> --- a/drivers/block/xen-blkback/common.h
> +++ b/drivers/block/xen-blkback/common.h
> @@ -254,7 +254,7 @@ struct backend_info;
> #define PERSISTENT_GNT_WAS_ACTIVE 1
>
> /* Number of requests that we can fit in a ring */
> -#define XEN_BLKIF_REQS 32
> +#define XEN_BLKIF_REQS (32 * XENBUS_MAX_RING_PAGES)
>
> struct persistent_gnt {
> struct page *page;
> @@ -326,6 +326,7 @@ struct xen_blkif {
> struct work_struct free_work;
> /* Thread shutdown wait queue. */
> wait_queue_head_t shutdown_wq;
> + int nr_ring_pages;
> };
>
> struct seg_buf {
> diff --git a/drivers/block/xen-blkback/xenbus.c
> b/drivers/block/xen-blkback/xenbus.c
> index ff30259..b75be66 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 +588,10 @@ static int xen_blkbk_probe(struct xenbus_device *dev,
> if (err)
> goto fail;
>
> + err = xenbus_printf(XBT_NIL, dev->nodename, "feature-multi-page-ring",
> "%u", 1);
> + if (err)
> + goto fail;
> +
> err = xenbus_switch_state(dev, XenbusStateInitWait);
> if (err)
> goto fail;
> @@ -852,22 +856,61 @@ 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",
> + 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;
> }
> + pr_info(DRV_PFX "event-channel %u\n", evtchn);
> +
> + 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_info(DRV_PFX "%s:using single page: ring-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/request %d ring pages
> exceed max",
> + 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_info(DRV_PFX "ring-ref%u: %d\n", i, ring_ref[i]);
> + }
> + }
>
> be->blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
> err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
> @@ -892,16 +935,16 @@ static int connect_ring(struct backend_info *be)
>
> be->blkif->vbd.feature_gnt_persistent = pers_grants;
> be->blkif->vbd.overflow_max_grants = 0;
> + be->blkif->nr_ring_pages = nr_grefs;
>
> - 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 2c61cf8..528e4f6 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, 0644);
> +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;
> - grant_ref_t gref;
> - int err;
> + 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-page-ring", "%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);
> @@ -1306,11 +1324,31 @@ 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);
> @@ -1338,6 +1376,7 @@ again:
> goto destroy_blkring;
> }
>
> + info->shadow[BLK_RING_SIZE-1].req.u.rw.id = 0x0fffffff;
> xenbus_switch_state(dev, XenbusStateInitialised);
>
> return 0;
> @@ -1422,21 +1461,13 @@ 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);
> dev_set_drvdata(&dev->dev, info);
>
> - err = talk_to_blkback(dev, info);
> - if (err) {
> - kfree(info);
> - dev_set_drvdata(&dev->dev, NULL);
> - return err;
> - }
> -
> return 0;
> }
>
> @@ -1476,7 +1507,7 @@ 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;
> @@ -1906,8 +1937,17 @@ static void blkback_changed(struct xenbus_device *dev,
> dev_dbg(&dev->dev, "blkfront:blkback_changed to state %d.\n",
> backend_state);
>
> switch (backend_state) {
> - case XenbusStateInitialising:
> case XenbusStateInitWait:
> + /*
> + * Talk to blkback after backend enter InitWait so we can know
> + * whether backend spports feature-multi-page-ring.
> + */
> + if (talk_to_blkback(dev, info)) {
> + kfree(info);
> + dev_set_drvdata(&dev->dev, NULL);
> + }
> + break;
> + case XenbusStateInitialising:
> case XenbusStateInitialised:
> case XenbusStateReconfiguring:
> case XenbusStateReconfigured:
> @@ -2088,6 +2128,9 @@ 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;
>
> diff --git a/include/xen/interface/io/blkif.h
> b/include/xen/interface/io/blkif.h
> index c33e1c4..9c2c9a7 100644
> --- a/include/xen/interface/io/blkif.h
> +++ b/include/xen/interface/io/blkif.h
> @@ -127,6 +127,19 @@ typedef uint64_t blkif_sector_t;
> #define BLKIF_OP_INDIRECT 6
>
> /*
> + * "feature-multi-page-ring" is introduced to use more than one page as the
> + * request ring between blkfront and backend. As a result, more reqs can be
> + * issued from blkfront and the performance get improved accordingly.
> + *
> + * If supported, the backend will write the key 'feature-multi-page-ring'
> + * for that vbd.
> + * Frontends that are aware of this feature and wish to use it will write key
> + * "max-ring-pages" to set the number of pages that they wish to be used as
> the
> + * ring. The 'xen_blkif_max_ring_pages' parameter is introduced with default
> + * number still one page, the maximum is XENBUS_MAX_RING_PAGES.
> + */
> +
> +/*
> * Maximum scatter/gather segments per request.
> * This is carefully chosen so that sizeof(struct blkif_ring) <= PAGE_SIZE.
> * NB. This could be 12 if the ring indexes weren't stored in the same page.
>
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