diff options
| -rw-r--r-- | migration/migration.c | 2 | ||||
| -rw-r--r-- | migration/migration.h | 2 | ||||
| -rw-r--r-- | migration/ram.c | 251 | ||||
| -rw-r--r-- | migration/trace-events | 7 |
4 files changed, 253 insertions, 9 deletions
diff --git a/migration/migration.c b/migration/migration.c index c965cae1d4..c5f0fdf8f8 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -3190,6 +3190,8 @@ static int postcopy_start(MigrationState *ms) MIGRATION_STATUS_FAILED); } + trace_postcopy_preempt_enabled(migrate_postcopy_preempt()); + return ret; fail_closefb: diff --git a/migration/migration.h b/migration/migration.h index 941c61e543..ff714c235f 100644 --- a/migration/migration.h +++ b/migration/migration.h @@ -68,7 +68,7 @@ typedef struct { struct MigrationIncomingState { QEMUFile *from_src_file; /* Previously received RAM's RAMBlock pointer */ - RAMBlock *last_recv_block; + RAMBlock *last_recv_block[RAM_CHANNEL_MAX]; /* A hook to allow cleanup at the end of incoming migration */ void *transport_data; void (*transport_cleanup)(void *data); diff --git a/migration/ram.c b/migration/ram.c index e4364c0bff..65b08c4edb 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -296,6 +296,20 @@ struct RAMSrcPageRequest { QSIMPLEQ_ENTRY(RAMSrcPageRequest) next_req; }; +typedef struct { + /* + * Cached ramblock/offset values if preempted. They're only meaningful if + * preempted==true below. + */ + RAMBlock *ram_block; + unsigned long ram_page; + /* + * Whether a postcopy preemption just happened. Will be reset after + * precopy recovered to background migration. + */ + bool preempted; +} PostcopyPreemptState; + /* State of RAM for migration */ struct RAMState { /* QEMUFile used for this migration */ @@ -350,6 +364,14 @@ struct RAMState { /* Queue of outstanding page requests from the destination */ QemuMutex src_page_req_mutex; QSIMPLEQ_HEAD(, RAMSrcPageRequest) src_page_requests; + + /* Postcopy preemption informations */ + PostcopyPreemptState postcopy_preempt_state; + /* + * Current channel we're using on src VM. Only valid if postcopy-preempt + * is enabled. + */ + unsigned int postcopy_channel; }; typedef struct RAMState RAMState; @@ -357,6 +379,11 @@ static RAMState *ram_state; static NotifierWithReturnList precopy_notifier_list; +static void postcopy_preempt_reset(RAMState *rs) +{ + memset(&rs->postcopy_preempt_state, 0, sizeof(PostcopyPreemptState)); +} + /* Whether postcopy has queued requests? */ static bool postcopy_has_request(RAMState *rs) { @@ -1947,6 +1974,55 @@ void ram_write_tracking_stop(void) } #endif /* defined(__linux__) */ +/* + * Check whether two addr/offset of the ramblock falls onto the same host huge + * page. Returns true if so, false otherwise. + */ +static bool offset_on_same_huge_page(RAMBlock *rb, uint64_t addr1, + uint64_t addr2) +{ + size_t page_size = qemu_ram_pagesize(rb); + + addr1 = ROUND_DOWN(addr1, page_size); + addr2 = ROUND_DOWN(addr2, page_size); + + return addr1 == addr2; +} + +/* + * Whether a previous preempted precopy huge page contains current requested + * page? Returns true if so, false otherwise. + * + * This should really happen very rarely, because it means when we were sending + * during background migration for postcopy we're sending exactly the page that + * some vcpu got faulted on on dest node. When it happens, we probably don't + * need to do much but drop the request, because we know right after we restore + * the precopy stream it'll be serviced. It'll slightly affect the order of + * postcopy requests to be serviced (e.g. it'll be the same as we move current + * request to the end of the queue) but it shouldn't be a big deal. The most + * imporant thing is we can _never_ try to send a partial-sent huge page on the + * POSTCOPY channel again, otherwise that huge page will got "split brain" on + * two channels (PRECOPY, POSTCOPY). + */ +static bool postcopy_preempted_contains(RAMState *rs, RAMBlock *block, + ram_addr_t offset) +{ + PostcopyPreemptState *state = &rs->postcopy_preempt_state; + + /* No preemption at all? */ + if (!state->preempted) { + return false; + } + + /* Not even the same ramblock? */ + if (state->ram_block != block) { + return false; + } + + return offset_on_same_huge_page(block, offset, + state->ram_page << TARGET_PAGE_BITS); +} + /** * get_queued_page: unqueue a page from the postcopy requests * @@ -1962,9 +2038,17 @@ static bool get_queued_page(RAMState *rs, PageSearchStatus *pss) RAMBlock *block; ram_addr_t offset; +again: block = unqueue_page(rs, &offset); - if (!block) { + if (block) { + /* See comment above postcopy_preempted_contains() */ + if (postcopy_preempted_contains(rs, block, offset)) { + trace_postcopy_preempt_hit(block->idstr, offset); + /* This request is dropped */ + goto again; + } + } else { /* * Poll write faults too if background snapshot is enabled; that's * when we have vcpus got blocked by the write protected pages. @@ -2180,6 +2264,117 @@ static int ram_save_target_page(RAMState *rs, PageSearchStatus *pss) return ram_save_page(rs, pss); } +static bool postcopy_needs_preempt(RAMState *rs, PageSearchStatus *pss) +{ + /* Not enabled eager preempt? Then never do that. */ + if (!migrate_postcopy_preempt()) { + return false; + } + + /* If the ramblock we're sending is a small page? Never bother. */ + if (qemu_ram_pagesize(pss->block) == TARGET_PAGE_SIZE) { + return false; + } + + /* Not in postcopy at all? */ + if (!migration_in_postcopy()) { + return false; + } + + /* + * If we're already handling a postcopy request, don't preempt as this page + * has got the same high priority. + */ + if (pss->postcopy_requested) { + return false; + } + + /* If there's postcopy requests, then check it up! */ + return postcopy_has_request(rs); +} + +/* Returns true if we preempted precopy, false otherwise */ +static void postcopy_do_preempt(RAMState *rs, PageSearchStatus *pss) +{ + PostcopyPreemptState *p_state = &rs->postcopy_preempt_state; + + trace_postcopy_preempt_triggered(pss->block->idstr, pss->page); + + /* + * Time to preempt precopy. Cache current PSS into preempt state, so that + * after handling the postcopy pages we can recover to it. We need to do + * so because the dest VM will have partial of the precopy huge page kept + * over in its tmp huge page caches; better move on with it when we can. + */ + p_state->ram_block = pss->block; + p_state->ram_page = pss->page; + p_state->preempted = true; +} + +/* Whether we're preempted by a postcopy request during sending a huge page */ +static bool postcopy_preempt_triggered(RAMState *rs) +{ + return rs->postcopy_preempt_state.preempted; +} + +static void postcopy_preempt_restore(RAMState *rs, PageSearchStatus *pss) +{ + PostcopyPreemptState *state = &rs->postcopy_preempt_state; + + assert(state->preempted); + + pss->block = state->ram_block; + pss->page = state->ram_page; + /* This is not a postcopy request but restoring previous precopy */ + pss->postcopy_requested = false; + + trace_postcopy_preempt_restored(pss->block->idstr, pss->page); + + /* Reset preempt state, most importantly, set preempted==false */ + postcopy_preempt_reset(rs); +} + +static void postcopy_preempt_choose_channel(RAMState *rs, PageSearchStatus *pss) +{ + MigrationState *s = migrate_get_current(); + unsigned int channel; + QEMUFile *next; + + channel = pss->postcopy_requested ? + RAM_CHANNEL_POSTCOPY : RAM_CHANNEL_PRECOPY; + + if (channel != rs->postcopy_channel) { + if (channel == RAM_CHANNEL_PRECOPY) { + next = s->to_dst_file; + } else { + next = s->postcopy_qemufile_src; + } + /* Update and cache the current channel */ + rs->f = next; + rs->postcopy_channel = channel; + + /* + * If channel switched, reset last_sent_block since the old sent block + * may not be on the same channel. + */ + rs->last_sent_block = NULL; + + trace_postcopy_preempt_switch_channel(channel); + } + + trace_postcopy_preempt_send_host_page(pss->block->idstr, pss->page); +} + +/* We need to make sure rs->f always points to the default channel elsewhere */ +static void postcopy_preempt_reset_channel(RAMState *rs) +{ + if (migrate_postcopy_preempt() && migration_in_postcopy()) { + rs->postcopy_channel = RAM_CHANNEL_PRECOPY; + rs->f = migrate_get_current()->to_dst_file; + trace_postcopy_preempt_reset_channel(); + } +} + /** * ram_save_host_page: save a whole host page * @@ -2211,7 +2406,16 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss) return 0; } + if (migrate_postcopy_preempt() && migration_in_postcopy()) { + postcopy_preempt_choose_channel(rs, pss); + } + do { + if (postcopy_needs_preempt(rs, pss)) { + postcopy_do_preempt(rs, pss); + break; + } + /* Check the pages is dirty and if it is send it */ if (migration_bitmap_clear_dirty(rs, pss->block, pss->page)) { tmppages = ram_save_target_page(rs, pss); @@ -2235,6 +2439,19 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss) /* The offset we leave with is the min boundary of host page and block */ pss->page = MIN(pss->page, hostpage_boundary); + /* + * When with postcopy preempt mode, flush the data as soon as possible for + * postcopy requests, because we've already sent a whole huge page, so the + * dst node should already have enough resource to atomically filling in + * the current missing page. + * + * More importantly, when using separate postcopy channel, we must do + * explicit flush or it won't flush until the buffer is full. + */ + if (migrate_postcopy_preempt() && pss->postcopy_requested) { + qemu_fflush(rs->f); + } + res = ram_save_release_protection(rs, pss, start_page); return (res < 0 ? res : pages); } @@ -2276,8 +2493,17 @@ static int ram_find_and_save_block(RAMState *rs) found = get_queued_page(rs, &pss); if (!found) { - /* priority queue empty, so just search for something dirty */ - found = find_dirty_block(rs, &pss, &again); + /* + * Recover previous precopy ramblock/offset if postcopy has + * preempted precopy. Otherwise find the next dirty bit. + */ + if (postcopy_preempt_triggered(rs)) { + postcopy_preempt_restore(rs, &pss); + found = true; + } else { + /* priority queue empty, so just search for something dirty */ + found = find_dirty_block(rs, &pss, &again); + } } if (found) { @@ -2405,6 +2631,8 @@ static void ram_state_reset(RAMState *rs) rs->last_page = 0; rs->last_version = ram_list.version; rs->xbzrle_enabled = false; + postcopy_preempt_reset(rs); + rs->postcopy_channel = RAM_CHANNEL_PRECOPY; } #define MAX_WAIT 50 /* ms, half buffered_file limit */ @@ -3048,6 +3276,8 @@ static int ram_save_iterate(QEMUFile *f, void *opaque) } qemu_mutex_unlock(&rs->bitmap_mutex); + postcopy_preempt_reset_channel(rs); + /* * Must occur before EOS (or any QEMUFile operation) * because of RDMA protocol. @@ -3125,6 +3355,8 @@ static int ram_save_complete(QEMUFile *f, void *opaque) return ret; } + postcopy_preempt_reset_channel(rs); + ret = multifd_send_sync_main(rs->f); if (ret < 0) { return ret; @@ -3209,11 +3441,13 @@ static int load_xbzrle(QEMUFile *f, ram_addr_t addr, void *host) * @mis: the migration incoming state pointer * @f: QEMUFile where to read the data from * @flags: Page flags (mostly to see if it's a continuation of previous block) + * @channel: the channel we're using */ static inline RAMBlock *ram_block_from_stream(MigrationIncomingState *mis, - QEMUFile *f, int flags) + QEMUFile *f, int flags, + int channel) { - RAMBlock *block = mis->last_recv_block; + RAMBlock *block = mis->last_recv_block[channel]; char id[256]; uint8_t len; @@ -3240,7 +3474,7 @@ static inline RAMBlock *ram_block_from_stream(MigrationIncomingState *mis, return NULL; } - mis->last_recv_block = block; + mis->last_recv_block[channel] = block; return block; } @@ -3694,7 +3928,7 @@ int ram_load_postcopy(QEMUFile *f, int channel) trace_ram_load_postcopy_loop(channel, (uint64_t)addr, flags); if (flags & (RAM_SAVE_FLAG_ZERO | RAM_SAVE_FLAG_PAGE | RAM_SAVE_FLAG_COMPRESS_PAGE)) { - block = ram_block_from_stream(mis, f, flags); + block = ram_block_from_stream(mis, f, flags, channel); if (!block) { ret = -EINVAL; break; @@ -3945,7 +4179,8 @@ static int ram_load_precopy(QEMUFile *f) if (flags & (RAM_SAVE_FLAG_ZERO | RAM_SAVE_FLAG_PAGE | RAM_SAVE_FLAG_COMPRESS_PAGE | RAM_SAVE_FLAG_XBZRLE)) { - RAMBlock *block = ram_block_from_stream(mis, f, flags); + RAMBlock *block = ram_block_from_stream(mis, f, flags, + RAM_CHANNEL_PRECOPY); host = host_from_ram_block_offset(block, addr); /* diff --git a/migration/trace-events b/migration/trace-events index 4bc787cf0c..69f311169a 100644 --- a/migration/trace-events +++ b/migration/trace-events @@ -111,6 +111,12 @@ ram_load_complete(int ret, uint64_t seq_iter) "exit_code %d seq iteration %" PRI ram_write_tracking_ramblock_start(const char *block_id, size_t page_size, void *addr, size_t length) "%s: page_size: %zu addr: %p length: %zu" ram_write_tracking_ramblock_stop(const char *block_id, size_t page_size, void *addr, size_t length) "%s: page_size: %zu addr: %p length: %zu" unqueue_page(char *block, uint64_t offset, bool dirty) "ramblock '%s' offset 0x%"PRIx64" dirty %d" +postcopy_preempt_triggered(char *str, unsigned long page) "during sending ramblock %s offset 0x%lx" +postcopy_preempt_restored(char *str, unsigned long page) "ramblock %s offset 0x%lx" +postcopy_preempt_hit(char *str, uint64_t offset) "ramblock %s offset 0x%"PRIx64 +postcopy_preempt_send_host_page(char *str, uint64_t offset) "ramblock %s offset 0x%"PRIx64 +postcopy_preempt_switch_channel(int channel) "%d" +postcopy_preempt_reset_channel(void) "" # multifd.c multifd_new_send_channel_async(uint8_t id) "channel %u" @@ -176,6 +182,7 @@ migration_thread_low_pending(uint64_t pending) "%" PRIu64 migrate_transferred(uint64_t tranferred, uint64_t time_spent, uint64_t bandwidth, uint64_t size) "transferred %" PRIu64 " time_spent %" PRIu64 " bandwidth %" PRIu64 " max_size %" PRId64 process_incoming_migration_co_end(int ret, int ps) "ret=%d postcopy-state=%d" process_incoming_migration_co_postcopy_end_main(void) "" +postcopy_preempt_enabled(bool value) "%d" # channel.c migration_set_incoming_channel(void *ioc, const char *ioctype) "ioc=%p ioctype=%s" |