diff options
| -rw-r--r-- | Documentation/ABI/stable/sysfs-bus-xen-backend | 10 | ||||
| -rw-r--r-- | drivers/block/xen-blkback/blkback.c | 287 | ||||
| -rw-r--r-- | drivers/block/xen-blkback/common.h | 18 | ||||
| -rw-r--r-- | drivers/block/xen-blkback/xenbus.c | 2 |
4 files changed, 260 insertions, 57 deletions
diff --git a/Documentation/ABI/stable/sysfs-bus-xen-backend b/Documentation/ABI/stable/sysfs-bus-xen-backend index e04afe0cca9..947db11350b 100644 --- a/Documentation/ABI/stable/sysfs-bus-xen-backend +++ b/Documentation/ABI/stable/sysfs-bus-xen-backend @@ -81,3 +81,13 @@ Contact: Roger Pau Monné <roger.pau@citrix.com> Description: Maximum number of free pages to keep in each block backend buffer. + +What: /sys/module/xen_blkback/parameters/max_persistent_grants +Date: March 2013 +KernelVersion: 3.10 +Contact: Roger Pau Monné <roger.pau@citrix.com> +Description: + Maximum number of grants to map persistently in + blkback. If the frontend tries to use more than + max_persistent_grants, the LRU kicks in and starts + removing 5% of max_persistent_grants every 100ms. diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c index 8245c6bb953..17052f74ebe 100644 --- a/drivers/block/xen-blkback/blkback.c +++ b/drivers/block/xen-blkback/blkback.c @@ -78,6 +78,36 @@ module_param_named(max_buffer_pages, xen_blkif_max_buffer_pages, int, 0644); MODULE_PARM_DESC(max_buffer_pages, "Maximum number of free pages to keep in each block backend buffer"); +/* + * Maximum number of grants to map persistently in blkback. For maximum + * performance this should be the total numbers of grants that can be used + * to fill the ring, but since this might become too high, specially with + * the use of indirect descriptors, we set it to a value that provides good + * performance without using too much memory. + * + * When the list of persistent grants is full we clean it up using a LRU + * algorithm. + */ + +static int xen_blkif_max_pgrants = 352; +module_param_named(max_persistent_grants, xen_blkif_max_pgrants, int, 0644); +MODULE_PARM_DESC(max_persistent_grants, + "Maximum number of grants to map persistently"); + +/* + * The LRU mechanism to clean the lists of persistent grants needs to + * be executed periodically. The time interval between consecutive executions + * of the purge mechanism is set in ms. + */ +#define LRU_INTERVAL 100 + +/* + * When the persistent grants list is full we will remove unused grants + * from the list. The percent number of grants to be removed at each LRU + * execution. + */ +#define LRU_PERCENT_CLEAN 5 + /* Run-time switchable: /sys/module/blkback/parameters/ */ static unsigned int log_stats; module_param(log_stats, int, 0644); @@ -96,8 +126,8 @@ struct pending_req { unsigned short operation; int status; struct list_head free_list; - DECLARE_BITMAP(unmap_seg, BLKIF_MAX_SEGMENTS_PER_REQUEST); struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST]; + struct persistent_gnt *persistent_gnts[BLKIF_MAX_SEGMENTS_PER_REQUEST]; }; #define BLKBACK_INVALID_HANDLE (~0) @@ -119,36 +149,6 @@ struct xen_blkbk { static struct xen_blkbk *blkbk; /* - * Maximum number of grant pages that can be mapped in blkback. - * BLKIF_MAX_SEGMENTS_PER_REQUEST * RING_SIZE is the maximum number of - * pages that blkback will persistently map. - * Currently, this is: - * RING_SIZE = 32 (for all known ring types) - * BLKIF_MAX_SEGMENTS_PER_REQUEST = 11 - * sizeof(struct persistent_gnt) = 48 - * So the maximum memory used to store the grants is: - * 32 * 11 * 48 = 16896 bytes - */ -static inline unsigned int max_mapped_grant_pages(enum blkif_protocol protocol) -{ - switch (protocol) { - case BLKIF_PROTOCOL_NATIVE: - return __CONST_RING_SIZE(blkif, PAGE_SIZE) * - BLKIF_MAX_SEGMENTS_PER_REQUEST; - case BLKIF_PROTOCOL_X86_32: - return __CONST_RING_SIZE(blkif_x86_32, PAGE_SIZE) * - BLKIF_MAX_SEGMENTS_PER_REQUEST; - case BLKIF_PROTOCOL_X86_64: - return __CONST_RING_SIZE(blkif_x86_64, PAGE_SIZE) * - BLKIF_MAX_SEGMENTS_PER_REQUEST; - default: - BUG(); - } - return 0; -} - - -/* * Little helpful macro to figure out the index and virtual address of the * pending_pages[..]. For each 'pending_req' we have have up to * BLKIF_MAX_SEGMENTS_PER_REQUEST (11) pages. The seg would be from 0 through @@ -239,13 +239,29 @@ static void make_response(struct xen_blkif *blkif, u64 id, (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL) -static int add_persistent_gnt(struct rb_root *root, +/* + * We don't need locking around the persistent grant helpers + * because blkback uses a single-thread for each backed, so we + * can be sure that this functions will never be called recursively. + * + * The only exception to that is put_persistent_grant, that can be called + * from interrupt context (by xen_blkbk_unmap), so we have to use atomic + * bit operations to modify the flags of a persistent grant and to count + * the number of used grants. + */ +static int add_persistent_gnt(struct xen_blkif *blkif, struct persistent_gnt *persistent_gnt) { - struct rb_node **new = &(root->rb_node), *parent = NULL; + struct rb_node **new = NULL, *parent = NULL; struct persistent_gnt *this; + if (blkif->persistent_gnt_c >= xen_blkif_max_pgrants) { + if (!blkif->vbd.overflow_max_grants) + blkif->vbd.overflow_max_grants = 1; + return -EBUSY; + } /* Figure out where to put new node */ + new = &blkif->persistent_gnts.rb_node; while (*new) { this = container_of(*new, struct persistent_gnt, node); @@ -260,18 +276,23 @@ static int add_persistent_gnt(struct rb_root *root, } } + bitmap_zero(persistent_gnt->flags, PERSISTENT_GNT_FLAGS_SIZE); + set_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags); /* Add new node and rebalance tree. */ rb_link_node(&(persistent_gnt->node), parent, new); - rb_insert_color(&(persistent_gnt->node), root); + rb_insert_color(&(persistent_gnt->node), &blkif->persistent_gnts); + blkif->persistent_gnt_c++; + atomic_inc(&blkif->persistent_gnt_in_use); return 0; } -static struct persistent_gnt *get_persistent_gnt(struct rb_root *root, +static struct persistent_gnt *get_persistent_gnt(struct xen_blkif *blkif, grant_ref_t gref) { struct persistent_gnt *data; - struct rb_node *node = root->rb_node; + struct rb_node *node = NULL; + node = blkif->persistent_gnts.rb_node; while (node) { data = container_of(node, struct persistent_gnt, node); @@ -279,12 +300,29 @@ static struct persistent_gnt *get_persistent_gnt(struct rb_root *root, node = node->rb_left; else if (gref > data->gnt) node = node->rb_right; - else + else { + if(test_bit(PERSISTENT_GNT_ACTIVE, data->flags)) { + pr_alert_ratelimited(DRV_PFX " requesting a grant already in use\n"); + return NULL; + } + set_bit(PERSISTENT_GNT_ACTIVE, data->flags); + atomic_inc(&blkif->persistent_gnt_in_use); return data; + } } return NULL; } +static void put_persistent_gnt(struct xen_blkif *blkif, + struct persistent_gnt *persistent_gnt) +{ + if(!test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags)) + pr_alert_ratelimited(DRV_PFX " freeing a grant already unused"); + set_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags); + clear_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags); + atomic_dec(&blkif->persistent_gnt_in_use); +} + static void free_persistent_gnts(struct xen_blkif *blkif, struct rb_root *root, unsigned int num) { @@ -322,6 +360,129 @@ static void free_persistent_gnts(struct xen_blkif *blkif, struct rb_root *root, BUG_ON(num != 0); } +static void unmap_purged_grants(struct work_struct *work) +{ + struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST]; + struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST]; + struct persistent_gnt *persistent_gnt; + int ret, segs_to_unmap = 0; + struct xen_blkif *blkif = container_of(work, typeof(*blkif), persistent_purge_work); + + while(!list_empty(&blkif->persistent_purge_list)) { + persistent_gnt = list_first_entry(&blkif->persistent_purge_list, + struct persistent_gnt, + remove_node); + list_del(&persistent_gnt->remove_node); + + gnttab_set_unmap_op(&unmap[segs_to_unmap], + vaddr(persistent_gnt->page), + GNTMAP_host_map, + persistent_gnt->handle); + + pages[segs_to_unmap] = persistent_gnt->page; + + if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST) { + ret = gnttab_unmap_refs(unmap, NULL, pages, + segs_to_unmap); + BUG_ON(ret); + put_free_pages(blkif, pages, segs_to_unmap); + segs_to_unmap = 0; + } + kfree(persistent_gnt); + } + if (segs_to_unmap > 0) { + ret = gnttab_unmap_refs(unmap, NULL, pages, segs_to_unmap); + BUG_ON(ret); + put_free_pages(blkif, pages, segs_to_unmap); + } +} + +static void purge_persistent_gnt(struct xen_blkif *blkif) +{ + struct persistent_gnt *persistent_gnt; + struct rb_node *n; + unsigned int num_clean, total; + bool scan_used = false; + struct rb_root *root; + + if (blkif->persistent_gnt_c < xen_blkif_max_pgrants || + (blkif->persistent_gnt_c == xen_blkif_max_pgrants && + !blkif->vbd.overflow_max_grants)) { + return; + } + + if (work_pending(&blkif->persistent_purge_work)) { + pr_alert_ratelimited(DRV_PFX "Scheduled work from previous purge is still pending, cannot purge list\n"); + return; + } + + num_clean = (xen_blkif_max_pgrants / 100) * LRU_PERCENT_CLEAN; + num_clean = blkif->persistent_gnt_c - xen_blkif_max_pgrants + num_clean; + num_clean = min(blkif->persistent_gnt_c, num_clean); + if (num_clean > + (blkif->persistent_gnt_c - + atomic_read(&blkif->persistent_gnt_in_use))) + return; + + /* + * At this point, we can assure that there will be no calls + * to get_persistent_grant (because we are executing this code from + * xen_blkif_schedule), there can only be calls to put_persistent_gnt, + * which means that the number of currently used grants will go down, + * but never up, so we will always be able to remove the requested + * number of grants. + */ + + total = num_clean; + + pr_debug(DRV_PFX "Going to purge %u persistent grants\n", num_clean); + + INIT_LIST_HEAD(&blkif->persistent_purge_list); + root = &blkif->persistent_gnts; +purge_list: + foreach_grant_safe(persistent_gnt, n, root, node) { + BUG_ON(persistent_gnt->handle == + BLKBACK_INVALID_HANDLE); + + if (test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags)) + continue; + if (!scan_used && + (test_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags))) + continue; + + rb_erase(&persistent_gnt->node, root); + list_add(&persistent_gnt->remove_node, + &blkif->persistent_purge_list); + if (--num_clean == 0) + goto finished; + } + /* + * If we get here it means we also need to start cleaning + * grants that were used since last purge in order to cope + * with the requested num + */ + if (!scan_used) { + pr_debug(DRV_PFX "Still missing %u purged frames\n", num_clean); + scan_used = true; + goto purge_list; + } +finished: + /* Remove the "used" flag from all the persistent grants */ + foreach_grant_safe(persistent_gnt, n, root, node) { + BUG_ON(persistent_gnt->handle == + BLKBACK_INVALID_HANDLE); + clear_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags); + } + blkif->persistent_gnt_c -= (total - num_clean); + blkif->vbd.overflow_max_grants = 0; + + /* We can defer this work */ + INIT_WORK(&blkif->persistent_purge_work, unmap_purged_grants); + schedule_work(&blkif->persistent_purge_work); + pr_debug(DRV_PFX "Purged %u/%u\n", (total - num_clean), total); + return; +} + /* * Retrieve from the 'pending_reqs' a free pending_req structure to be used. */ @@ -453,12 +614,12 @@ irqreturn_t xen_blkif_be_int(int irq, void *dev_id) static void print_stats(struct xen_blkif *blkif) { pr_info("xen-blkback (%s): oo %3llu | rd %4llu | wr %4llu | f %4llu" - " | ds %4llu | pg: %4u/%4u\n", + " | ds %4llu | pg: %4u/%4d\n", current->comm, blkif->st_oo_req, blkif->st_rd_req, blkif->st_wr_req, blkif->st_f_req, blkif->st_ds_req, blkif->persistent_gnt_c, - max_mapped_grant_pages(blkif->blk_protocol)); + xen_blkif_max_pgrants); blkif->st_print = jiffies + msecs_to_jiffies(10 * 1000); blkif->st_rd_req = 0; blkif->st_wr_req = 0; @@ -470,6 +631,7 @@ int xen_blkif_schedule(void *arg) { struct xen_blkif *blkif = arg; struct xen_vbd *vbd = &blkif->vbd; + unsigned long timeout; xen_blkif_get(blkif); @@ -479,13 +641,21 @@ int xen_blkif_schedule(void *arg) if (unlikely(vbd->size != vbd_sz(vbd))) xen_vbd_resize(blkif); - wait_event_interruptible( + timeout = msecs_to_jiffies(LRU_INTERVAL); + + timeout = wait_event_interruptible_timeout( blkif->wq, - blkif->waiting_reqs || kthread_should_stop()); - wait_event_interruptible( + blkif->waiting_reqs || kthread_should_stop(), + timeout); + if (timeout == 0) + goto purge_gnt_list; + timeout = wait_event_interruptible_timeout( blkbk->pending_free_wq, !list_empty(&blkbk->pending_free) || - kthread_should_stop()); + kthread_should_stop(), + timeout); + if (timeout == 0) + goto purge_gnt_list; blkif->waiting_reqs = 0; smp_mb(); /* clear flag *before* checking for work */ @@ -493,6 +663,13 @@ int xen_blkif_schedule(void *arg) if (do_block_io_op(blkif)) blkif->waiting_reqs = 1; +purge_gnt_list: + if (blkif->vbd.feature_gnt_persistent && + time_after(jiffies, blkif->next_lru)) { + purge_persistent_gnt(blkif); + blkif->next_lru = jiffies + msecs_to_jiffies(LRU_INTERVAL); + } + /* Shrink if we have more than xen_blkif_max_buffer_pages */ shrink_free_pagepool(blkif, xen_blkif_max_buffer_pages); @@ -538,8 +715,10 @@ static void xen_blkbk_unmap(struct pending_req *req) int ret; for (i = 0; i < req->nr_pages; i++) { - if (!test_bit(i, req->unmap_seg)) + if (req->persistent_gnts[i] != NULL) { + put_persistent_gnt(blkif, req->persistent_gnts[i]); continue; + } handle = pending_handle(req, i); pages[invcount] = req->pages[i]; if (handle == BLKBACK_INVALID_HANDLE) @@ -561,8 +740,8 @@ static int xen_blkbk_map(struct blkif_request *req, struct page *pages[]) { struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST]; - struct persistent_gnt *persistent_gnts[BLKIF_MAX_SEGMENTS_PER_REQUEST]; struct page *pages_to_gnt[BLKIF_MAX_SEGMENTS_PER_REQUEST]; + struct persistent_gnt **persistent_gnts = pending_req->persistent_gnts; struct persistent_gnt *persistent_gnt = NULL; struct xen_blkif *blkif = pending_req->blkif; phys_addr_t addr = 0; @@ -574,9 +753,6 @@ static int xen_blkbk_map(struct blkif_request *req, use_persistent_gnts = (blkif->vbd.feature_gnt_persistent); - BUG_ON(blkif->persistent_gnt_c > - max_mapped_grant_pages(pending_req->blkif->blk_protocol)); - /* * Fill out preq.nr_sects with proper amount of sectors, and setup * assign map[..] with the PFN of the page in our domain with the @@ -587,7 +763,7 @@ static int xen_blkbk_map(struct blkif_request *req, if (use_persistent_gnts) persistent_gnt = get_persistent_gnt( - &blkif->persistent_gnts, + blkif, req->u.rw.seg[i].gref); if (persistent_gnt) { @@ -623,7 +799,6 @@ static int xen_blkbk_map(struct blkif_request *req, * so that when we access vaddr(pending_req,i) it has the contents of * the page from the other domain. */ - bitmap_zero(pending_req->unmap_seg, BLKIF_MAX_SEGMENTS_PER_REQUEST); for (seg_idx = 0, new_map_idx = 0; seg_idx < nseg; seg_idx++) { if (!persistent_gnts[seg_idx]) { /* This is a newly mapped grant */ @@ -646,11 +821,10 @@ static int xen_blkbk_map(struct blkif_request *req, goto next; } if (use_persistent_gnts && - blkif->persistent_gnt_c < - max_mapped_grant_pages(blkif->blk_protocol)) { + blkif->persistent_gnt_c < xen_blkif_max_pgrants) { /* * We are using persistent grants, the grant is - * not mapped but we have room for it + * not mapped but we might have room for it. */ persistent_gnt = kmalloc(sizeof(struct persistent_gnt), GFP_KERNEL); @@ -665,16 +839,16 @@ static int xen_blkbk_map(struct blkif_request *req, persistent_gnt->gnt = map[new_map_idx].ref; persistent_gnt->handle = map[new_map_idx].handle; persistent_gnt->page = pages[seg_idx]; - if (add_persistent_gnt(&blkif->persistent_gnts, + if (add_persistent_gnt(blkif, persistent_gnt)) { kfree(persistent_gnt); persistent_gnt = NULL; goto next_unmap; } - blkif->persistent_gnt_c++; + persistent_gnts[seg_idx] = persistent_gnt; pr_debug(DRV_PFX " grant %u added to the tree of persistent grants, using %u/%u\n", persistent_gnt->gnt, blkif->persistent_gnt_c, - max_mapped_grant_pages(blkif->blk_protocol)); + xen_blkif_max_pgrants); new_map_idx++; goto next; } @@ -688,7 +862,6 @@ next_unmap: * We could not map this grant persistently, so use it as * a non-persistent grant. */ - bitmap_set(pending_req->unmap_seg, seg_idx, 1); new_map_idx++; next: seg[seg_idx].offset = (req->u.rw.seg[seg_idx].first_sect << 9); diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h index 6c73c3855e6..af9bed48f77 100644 --- a/drivers/block/xen-blkback/common.h +++ b/drivers/block/xen-blkback/common.h @@ -182,12 +182,23 @@ struct xen_vbd { struct backend_info; +/* Number of available flags */ +#define PERSISTENT_GNT_FLAGS_SIZE 2 +/* This persistent grant is currently in use */ +#define PERSISTENT_GNT_ACTIVE 0 +/* + * This persistent grant has been used, this flag is set when we remove the + * PERSISTENT_GNT_ACTIVE, to know that this grant has been used recently. + */ +#define PERSISTENT_GNT_WAS_ACTIVE 1 struct persistent_gnt { struct page *page; grant_ref_t gnt; grant_handle_t handle; + DECLARE_BITMAP(flags, PERSISTENT_GNT_FLAGS_SIZE); struct rb_node node; + struct list_head remove_node; }; struct xen_blkif { @@ -219,6 +230,12 @@ struct xen_blkif { /* tree to store persistent grants */ struct rb_root persistent_gnts; unsigned int persistent_gnt_c; + atomic_t persistent_gnt_in_use; + unsigned long next_lru; + + /* used by the kworker that offload work from the persistent purge */ + struct list_head persistent_purge_list; + struct work_struct persistent_purge_work; /* buffer of free pages to map grant refs */ spinlock_t free_pages_lock; @@ -262,6 +279,7 @@ int xen_blkif_xenbus_init(void); irqreturn_t xen_blkif_be_int(int irq, void *dev_id); int xen_blkif_schedule(void *arg); +int xen_blkif_purge_persistent(void *arg); int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt, struct backend_info *be, int state); diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c index 24f7f6d8771..e0fd92a2a4c 100644 --- a/drivers/block/xen-blkback/xenbus.c +++ b/drivers/block/xen-blkback/xenbus.c @@ -98,6 +98,7 @@ static void xen_update_blkif_status(struct xen_blkif *blkif) err = PTR_ERR(blkif->xenblkd); blkif->xenblkd = NULL; xenbus_dev_error(blkif->be->dev, err, "start xenblkd"); + return; } } @@ -121,6 +122,7 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid) spin_lock_init(&blkif->free_pages_lock); INIT_LIST_HEAD(&blkif->free_pages); blkif->free_pages_num = 0; + atomic_set(&blkif->persistent_gnt_in_use, 0); return blkif; } |