diff options
| -rw-r--r-- | include/exec/ram_addr.h | 76 | ||||
| -rw-r--r-- | migration/migration.c | 4 | ||||
| -rw-r--r-- | migration/migration.h | 27 | ||||
| -rw-r--r-- | migration/ram.c | 44 | ||||
| -rw-r--r-- | migration/trace-events | 1 |
5 files changed, 150 insertions, 2 deletions
diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h index 222b4338fb..b7b2e60ff6 100644 --- a/include/exec/ram_addr.h +++ b/include/exec/ram_addr.h @@ -51,8 +51,70 @@ struct RAMBlock { unsigned long *unsentmap; /* bitmap of already received pages in postcopy */ unsigned long *receivedmap; + + /* + * bitmap to track already cleared dirty bitmap. When the bit is + * set, it means the corresponding memory chunk needs a log-clear. + * Set this up to non-NULL to enable the capability to postpone + * and split clearing of dirty bitmap on the remote node (e.g., + * KVM). The bitmap will be set only when doing global sync. + * + * NOTE: this bitmap is different comparing to the other bitmaps + * in that one bit can represent multiple guest pages (which is + * decided by the `clear_bmap_shift' variable below). On + * destination side, this should always be NULL, and the variable + * `clear_bmap_shift' is meaningless. + */ + unsigned long *clear_bmap; + uint8_t clear_bmap_shift; }; +/** + * clear_bmap_size: calculate clear bitmap size + * + * @pages: number of guest pages + * @shift: guest page number shift + * + * Returns: number of bits for the clear bitmap + */ +static inline long clear_bmap_size(uint64_t pages, uint8_t shift) +{ + return DIV_ROUND_UP(pages, 1UL << shift); +} + +/** + * clear_bmap_set: set clear bitmap for the page range + * + * @rb: the ramblock to operate on + * @start: the start page number + * @size: number of pages to set in the bitmap + * + * Returns: None + */ +static inline void clear_bmap_set(RAMBlock *rb, uint64_t start, + uint64_t npages) +{ + uint8_t shift = rb->clear_bmap_shift; + + bitmap_set_atomic(rb->clear_bmap, start >> shift, + clear_bmap_size(npages, shift)); +} + +/** + * clear_bmap_test_and_clear: test clear bitmap for the page, clear if set + * + * @rb: the ramblock to operate on + * @page: the page number to check + * + * Returns: true if the bit was set, false otherwise + */ +static inline bool clear_bmap_test_and_clear(RAMBlock *rb, uint64_t page) +{ + uint8_t shift = rb->clear_bmap_shift; + + return bitmap_test_and_clear_atomic(rb->clear_bmap, page >> shift, 1); +} + static inline bool offset_in_ramblock(RAMBlock *b, ram_addr_t offset) { return (b && b->host && offset < b->used_length) ? true : false; @@ -463,8 +525,18 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb, } } - /* TODO: split the huge bitmap into smaller chunks */ - memory_region_clear_dirty_bitmap(rb->mr, start, length); + if (rb->clear_bmap) { + /* + * Postpone the dirty bitmap clear to the point before we + * really send the pages, also we will split the clear + * dirty procedure into smaller chunks. + */ + clear_bmap_set(rb, start >> TARGET_PAGE_BITS, + length >> TARGET_PAGE_BITS); + } else { + /* Slow path - still do that in a huge chunk */ + memory_region_clear_dirty_bitmap(rb->mr, start, length); + } } else { ram_addr_t offset = rb->offset; diff --git a/migration/migration.c b/migration/migration.c index 2865ae3fa9..8a607fe1e2 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -3362,6 +3362,8 @@ void migration_global_dump(Monitor *mon) ms->send_section_footer ? "on" : "off"); monitor_printf(mon, "decompress-error-check: %s\n", ms->decompress_error_check ? "on" : "off"); + monitor_printf(mon, "clear-bitmap-shift: %u\n", + ms->clear_bitmap_shift); } #define DEFINE_PROP_MIG_CAP(name, x) \ @@ -3376,6 +3378,8 @@ static Property migration_properties[] = { send_section_footer, true), DEFINE_PROP_BOOL("decompress-error-check", MigrationState, decompress_error_check, true), + DEFINE_PROP_UINT8("x-clear-bitmap-shift", MigrationState, + clear_bitmap_shift, CLEAR_BITMAP_SHIFT_DEFAULT), /* Migration parameters */ DEFINE_PROP_UINT8("x-compress-level", MigrationState, diff --git a/migration/migration.h b/migration/migration.h index 5e8f09c6db..1fdd7b21fd 100644 --- a/migration/migration.h +++ b/migration/migration.h @@ -26,6 +26,23 @@ struct PostcopyBlocktimeContext; #define MIGRATION_RESUME_ACK_VALUE (1) +/* + * 1<<6=64 pages -> 256K chunk when page size is 4K. This gives us + * the benefit that all the chunks are 64 pages aligned then the + * bitmaps are always aligned to LONG. + */ +#define CLEAR_BITMAP_SHIFT_MIN 6 +/* + * 1<<18=256K pages -> 1G chunk when page size is 4K. This is the + * default value to use if no one specified. + */ +#define CLEAR_BITMAP_SHIFT_DEFAULT 18 +/* + * 1<<31=2G pages -> 8T chunk when page size is 4K. This should be + * big enough and make sure we won't overflow easily. + */ +#define CLEAR_BITMAP_SHIFT_MAX 31 + /* State for the incoming migration */ struct MigrationIncomingState { QEMUFile *from_src_file; @@ -232,6 +249,16 @@ struct MigrationState * do not trigger spurious decompression errors. */ bool decompress_error_check; + + /* + * This decides the size of guest memory chunk that will be used + * to track dirty bitmap clearing. The size of memory chunk will + * be GUEST_PAGE_SIZE << N. Say, N=0 means we will clear dirty + * bitmap for each page to send (1<<0=1); N=10 means we will clear + * dirty bitmap only once for 1<<10=1K continuous guest pages + * (which is in 4M chunk). + */ + uint8_t clear_bitmap_shift; }; void migrate_set_state(int *state, int old_state, int new_state); diff --git a/migration/ram.c b/migration/ram.c index 48969db84b..8a6ad61d3d 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -1664,6 +1664,33 @@ static inline bool migration_bitmap_clear_dirty(RAMState *rs, bool ret; qemu_mutex_lock(&rs->bitmap_mutex); + + /* + * Clear dirty bitmap if needed. This _must_ be called before we + * send any of the page in the chunk because we need to make sure + * we can capture further page content changes when we sync dirty + * log the next time. So as long as we are going to send any of + * the page in the chunk we clear the remote dirty bitmap for all. + * Clearing it earlier won't be a problem, but too late will. + */ + if (rb->clear_bmap && clear_bmap_test_and_clear(rb, page)) { + uint8_t shift = rb->clear_bmap_shift; + hwaddr size = 1ULL << (TARGET_PAGE_BITS + shift); + hwaddr start = (page << TARGET_PAGE_BITS) & (-size); + + /* + * CLEAR_BITMAP_SHIFT_MIN should always guarantee this... this + * can make things easier sometimes since then start address + * of the small chunk will always be 64 pages aligned so the + * bitmap will always be aligned to unsigned long. We should + * even be able to remove this restriction but I'm simply + * keeping it. + */ + assert(shift >= 6); + trace_migration_bitmap_clear_dirty(rb->idstr, start, size, page); + memory_region_clear_dirty_bitmap(rb->mr, start, size); + } + ret = test_and_clear_bit(page, rb->bmap); if (ret) { @@ -2687,6 +2714,8 @@ static void ram_save_cleanup(void *opaque) memory_global_dirty_log_stop(); RAMBLOCK_FOREACH_NOT_IGNORED(block) { + g_free(block->clear_bmap); + block->clear_bmap = NULL; g_free(block->bmap); block->bmap = NULL; g_free(block->unsentmap); @@ -3197,11 +3226,24 @@ static int ram_state_init(RAMState **rsp) static void ram_list_init_bitmaps(void) { + MigrationState *ms = migrate_get_current(); RAMBlock *block; unsigned long pages; + uint8_t shift; /* Skip setting bitmap if there is no RAM */ if (ram_bytes_total()) { + shift = ms->clear_bitmap_shift; + if (shift > CLEAR_BITMAP_SHIFT_MAX) { + error_report("clear_bitmap_shift (%u) too big, using " + "max value (%u)", shift, CLEAR_BITMAP_SHIFT_MAX); + shift = CLEAR_BITMAP_SHIFT_MAX; + } else if (shift < CLEAR_BITMAP_SHIFT_MIN) { + error_report("clear_bitmap_shift (%u) too small, using " + "min value (%u)", shift, CLEAR_BITMAP_SHIFT_MIN); + shift = CLEAR_BITMAP_SHIFT_MIN; + } + RAMBLOCK_FOREACH_NOT_IGNORED(block) { pages = block->max_length >> TARGET_PAGE_BITS; /* @@ -3214,6 +3256,8 @@ static void ram_list_init_bitmaps(void) * Here setting RAMBlock.bmap would be fine too but not necessary. */ block->bmap = bitmap_new(pages); + block->clear_bmap_shift = shift; + block->clear_bmap = bitmap_new(clear_bmap_size(pages, shift)); if (migrate_postcopy_ram()) { block->unsentmap = bitmap_new(pages); bitmap_set(block->unsentmap, 0, pages); diff --git a/migration/trace-events b/migration/trace-events index cd50a1e659..d8e54c367a 100644 --- a/migration/trace-events +++ b/migration/trace-events @@ -79,6 +79,7 @@ get_queued_page(const char *block_name, uint64_t tmp_offset, unsigned long page_ get_queued_page_not_dirty(const char *block_name, uint64_t tmp_offset, unsigned long page_abs, int sent) "%s/0x%" PRIx64 " page_abs=0x%lx (sent=%d)" migration_bitmap_sync_start(void) "" migration_bitmap_sync_end(uint64_t dirty_pages) "dirty_pages %" PRIu64 +migration_bitmap_clear_dirty(char *str, uint64_t start, uint64_t size, unsigned long page) "rb %s start 0x%"PRIx64" size 0x%"PRIx64" page 0x%lx" migration_throttle(void) "" multifd_recv(uint8_t id, uint64_t packet_num, uint32_t used, uint32_t flags, uint32_t next_packet_size) "channel %d packet_num %" PRIu64 " pages %d flags 0x%x next packet size %d" multifd_recv_sync_main(long packet_num) "packet num %ld" |