Juan Quintela had a patchset enabling zero page checking in multifd threads.
https://lore.kernel.org/all/20220802063907.18882-13-quint...@redhat.com/ Some of the changes in that patchset has already made to upstream but a few are still being reviewed. This patch contains the changes from the remaining patches. This change serves as the baseline for DSA offloading. * multifd: Add capability to enable/disable zero_page * migration: Export ram_release_page() * multifd: Support for zero pages transmission * multifd: Zero pages transmission * So we use multifd to transmit zero pages. --- migration/migration-stats.h | 8 +-- migration/multifd.c | 105 ++++++++++++++++++++++++++++-------- migration/multifd.h | 19 ++++++- migration/options.c | 12 +++++ migration/options.h | 1 + migration/ram.c | 47 +++++++++++++--- migration/trace-events | 8 +-- qapi/migration.json | 7 ++- 8 files changed, 167 insertions(+), 40 deletions(-) diff --git a/migration/migration-stats.h b/migration/migration-stats.h index 2358caad63..dca3c100b0 100644 --- a/migration/migration-stats.h +++ b/migration/migration-stats.h @@ -68,6 +68,10 @@ typedef struct { * Number of pages transferred that were not full of zeros. */ Stat64 normal_pages; + /* + * Number of pages transferred that were full of zeros. + */ + Stat64 zero_pages; /* * Number of bytes sent during postcopy. */ @@ -97,10 +101,6 @@ typedef struct { * Total number of bytes transferred. */ Stat64 transferred; - /* - * Number of pages transferred that were full of zeros. - */ - Stat64 zero_pages; } MigrationAtomicStats; extern MigrationAtomicStats mig_stats; diff --git a/migration/multifd.c b/migration/multifd.c index 0f6b203877..452fb158b8 100644 --- a/migration/multifd.c +++ b/migration/multifd.c @@ -12,6 +12,7 @@ #include "qemu/osdep.h" #include "qemu/rcu.h" +#include "qemu/cutils.h" #include "exec/target_page.h" #include "sysemu/sysemu.h" #include "exec/ramblock.h" @@ -268,6 +269,7 @@ static void multifd_send_fill_packet(MultiFDSendParams *p) packet->normal_pages = cpu_to_be32(p->normal_num); packet->next_packet_size = cpu_to_be32(p->next_packet_size); packet->packet_num = cpu_to_be64(p->packet_num); + packet->zero_pages = cpu_to_be32(p->zero_num); if (p->pages->block) { strncpy(packet->ramblock, p->pages->block->idstr, 256); @@ -279,6 +281,12 @@ static void multifd_send_fill_packet(MultiFDSendParams *p) packet->offset[i] = cpu_to_be64(temp); } + for (i = 0; i < p->zero_num; i++) { + /* there are architectures where ram_addr_t is 32 bit */ + uint64_t temp = p->zero[i]; + + packet->offset[p->normal_num + i] = cpu_to_be64(temp); + } } static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp) @@ -327,7 +335,15 @@ static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp) p->next_packet_size = be32_to_cpu(packet->next_packet_size); p->packet_num = be64_to_cpu(packet->packet_num); - if (p->normal_num == 0) { + p->zero_num = be32_to_cpu(packet->zero_pages); + if (p->zero_num > packet->pages_alloc - p->normal_num) { + error_setg(errp, "multifd: received packet " + "with %u zero pages and expected maximum pages are %u", + p->zero_num, packet->pages_alloc - p->normal_num) ; + return -1; + } + + if (p->normal_num == 0 && p->zero_num == 0) { return 0; } @@ -353,6 +369,18 @@ static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp) p->normal[i] = offset; } + for (i = 0; i < p->zero_num; i++) { + uint64_t offset = be64_to_cpu(packet->offset[p->normal_num + i]); + + if (offset > (p->block->used_length - p->page_size)) { + error_setg(errp, "multifd: offset too long %" PRIu64 + " (max " RAM_ADDR_FMT ")", + offset, p->block->used_length); + return -1; + } + p->zero[i] = offset; + } + return 0; } @@ -432,6 +460,8 @@ static int multifd_send_pages(QEMUFile *f) p->packet_num = multifd_send_state->packet_num++; multifd_send_state->pages = p->pages; p->pages = pages; + stat64_add(&mig_stats.normal_pages, p->normal_num); + stat64_add(&mig_stats.zero_pages, p->zero_num); qemu_mutex_unlock(&p->mutex); qemu_sem_post(&p->sem); @@ -548,6 +578,8 @@ void multifd_save_cleanup(void) p->iov = NULL; g_free(p->normal); p->normal = NULL; + g_free(p->zero); + p->zero = NULL; multifd_send_state->ops->send_cleanup(p, &local_err); if (local_err) { migrate_set_error(migrate_get_current(), local_err); @@ -622,7 +654,7 @@ int multifd_send_sync_main(QEMUFile *f) } p->packet_num = multifd_send_state->packet_num++; - p->flags |= MULTIFD_FLAG_SYNC; + p->sync_needed = true; p->pending_job++; qemu_mutex_unlock(&p->mutex); qemu_sem_post(&p->sem); @@ -648,6 +680,8 @@ static void *multifd_send_thread(void *opaque) MultiFDSendParams *p = opaque; MigrationThread *thread = NULL; Error *local_err = NULL; + /* older qemu don't understand zero page on multifd channel */ + bool use_multifd_zero_page = !migrate_use_main_zero_page(); int ret = 0; bool use_zero_copy_send = migrate_zero_copy_send(); @@ -673,9 +707,17 @@ static void *multifd_send_thread(void *opaque) qemu_mutex_lock(&p->mutex); if (p->pending_job) { + RAMBlock *rb = p->pages->block; uint64_t packet_num = p->packet_num; - uint32_t flags; + p->flags = 0; + if (p->sync_needed) { + p->flags |= MULTIFD_FLAG_SYNC; + p->sync_needed = false; + } + qemu_mutex_unlock(&p->mutex); + p->normal_num = 0; + p->zero_num = 0; if (use_zero_copy_send) { p->iovs_num = 0; @@ -684,27 +726,27 @@ static void *multifd_send_thread(void *opaque) } for (int i = 0; i < p->pages->num; i++) { - p->normal[p->normal_num] = p->pages->offset[i]; - p->normal_num++; + uint64_t offset = p->pages->offset[i]; + if (use_multifd_zero_page && + buffer_is_zero(rb->host + offset, p->page_size)) { + p->zero[p->zero_num] = offset; + p->zero_num++; + ram_release_page(rb->idstr, offset); + } else { + p->normal[p->normal_num] = offset; + p->normal_num++; + } } if (p->normal_num) { ret = multifd_send_state->ops->send_prepare(p, &local_err); if (ret != 0) { - qemu_mutex_unlock(&p->mutex); break; } } multifd_send_fill_packet(p); - flags = p->flags; - p->flags = 0; - p->num_packets++; - p->total_normal_pages += p->normal_num; - p->pages->num = 0; - p->pages->block = NULL; - qemu_mutex_unlock(&p->mutex); - trace_multifd_send(p->id, packet_num, p->normal_num, flags, + trace_multifd_send(p->id, packet_num, p->normal_num, p->zero_num, p->flags, p->next_packet_size); if (use_zero_copy_send) { @@ -731,10 +773,15 @@ static void *multifd_send_thread(void *opaque) stat64_add(&mig_stats.multifd_bytes, p->next_packet_size); stat64_add(&mig_stats.transferred, p->next_packet_size); qemu_mutex_lock(&p->mutex); + p->num_packets++; + p->total_normal_pages += p->normal_num; + p->total_zero_pages += p->zero_num; + p->pages->num = 0; + p->pages->block = NULL; p->pending_job--; qemu_mutex_unlock(&p->mutex); - if (flags & MULTIFD_FLAG_SYNC) { + if (p->flags & MULTIFD_FLAG_SYNC) { qemu_sem_post(&p->sem_sync); } } else if (p->quit) { @@ -768,7 +815,8 @@ out: rcu_unregister_thread(); migration_threads_remove(thread); - trace_multifd_send_thread_end(p->id, p->num_packets, p->total_normal_pages); + trace_multifd_send_thread_end(p->id, p->num_packets, p->total_normal_pages, + p->total_zero_pages); return NULL; } @@ -944,6 +992,7 @@ int multifd_save_setup(Error **errp) p->normal = g_new0(ram_addr_t, page_count); p->page_size = qemu_target_page_size(); p->page_count = page_count; + p->zero = g_new0(ram_addr_t, page_count); if (migrate_zero_copy_send()) { p->write_flags = QIO_CHANNEL_WRITE_FLAG_ZERO_COPY; @@ -1059,6 +1108,8 @@ void multifd_load_cleanup(void) p->iov = NULL; g_free(p->normal); p->normal = NULL; + g_free(p->zero); + p->zero = NULL; multifd_recv_state->ops->recv_cleanup(p); } qemu_sem_destroy(&multifd_recv_state->sem_sync); @@ -1105,7 +1156,7 @@ static void *multifd_recv_thread(void *opaque) rcu_register_thread(); while (true) { - uint32_t flags; + bool sync_needed = false; if (p->quit) { break; @@ -1124,13 +1175,14 @@ static void *multifd_recv_thread(void *opaque) break; } - flags = p->flags; + trace_multifd_recv(p->id, p->packet_num, p->normal_num, p->zero_num, + p->flags, p->next_packet_size); + sync_needed = p->flags & MULTIFD_FLAG_SYNC; /* recv methods don't know how to handle the SYNC flag */ p->flags &= ~MULTIFD_FLAG_SYNC; - trace_multifd_recv(p->id, p->packet_num, p->normal_num, flags, - p->next_packet_size); p->num_packets++; p->total_normal_pages += p->normal_num; + p->total_zero_pages += p->zero_num; qemu_mutex_unlock(&p->mutex); if (p->normal_num) { @@ -1140,7 +1192,14 @@ static void *multifd_recv_thread(void *opaque) } } - if (flags & MULTIFD_FLAG_SYNC) { + for (int i = 0; i < p->zero_num; i++) { + void *page = p->host + p->zero[i]; + if (!buffer_is_zero(page, p->page_size)) { + memset(page, 0, p->page_size); + } + } + + if (sync_needed) { qemu_sem_post(&multifd_recv_state->sem_sync); qemu_sem_wait(&p->sem_sync); } @@ -1155,7 +1214,8 @@ static void *multifd_recv_thread(void *opaque) qemu_mutex_unlock(&p->mutex); rcu_unregister_thread(); - trace_multifd_recv_thread_end(p->id, p->num_packets, p->total_normal_pages); + trace_multifd_recv_thread_end(p->id, p->num_packets, p->total_normal_pages, + p->total_zero_pages); return NULL; } @@ -1196,6 +1256,7 @@ int multifd_load_setup(Error **errp) p->normal = g_new0(ram_addr_t, page_count); p->page_count = page_count; p->page_size = qemu_target_page_size(); + p->zero = g_new0(ram_addr_t, page_count); } for (i = 0; i < thread_count; i++) { diff --git a/migration/multifd.h b/migration/multifd.h index a835643b48..e8f90776bb 100644 --- a/migration/multifd.h +++ b/migration/multifd.h @@ -48,7 +48,10 @@ typedef struct { /* size of the next packet that contains pages */ uint32_t next_packet_size; uint64_t packet_num; - uint64_t unused[4]; /* Reserved for future use */ + /* zero pages */ + uint32_t zero_pages; + uint32_t unused32[1]; /* Reserved for future use */ + uint64_t unused64[3]; /* Reserved for future use */ char ramblock[256]; uint64_t offset[]; } __attribute__((packed)) MultiFDPacket_t; @@ -118,10 +121,14 @@ typedef struct { MultiFDPacket_t *packet; /* size of the next packet that contains pages */ uint32_t next_packet_size; + /* Do we need to do an iteration sync */ + bool sync_needed; /* packets sent through this channel */ uint64_t num_packets; /* non zero pages sent through this channel */ uint64_t total_normal_pages; + /* zero pages sent through this channel */ + uint64_t total_zero_pages; /* buffers to send */ struct iovec *iov; /* number of iovs used */ @@ -130,6 +137,10 @@ typedef struct { ram_addr_t *normal; /* num of non zero pages */ uint32_t normal_num; + /* Pages that are zero */ + ram_addr_t *zero; + /* num of zero pages */ + uint32_t zero_num; /* used for compression methods */ void *data; } MultiFDSendParams; @@ -181,12 +192,18 @@ typedef struct { uint8_t *host; /* non zero pages recv through this channel */ uint64_t total_normal_pages; + /* zero pages recv through this channel */ + uint64_t total_zero_pages; /* buffers to recv */ struct iovec *iov; /* Pages that are not zero */ ram_addr_t *normal; /* num of non zero pages */ uint32_t normal_num; + /* Pages that are zero */ + ram_addr_t *zero; + /* num of zero pages */ + uint32_t zero_num; /* used for de-compression methods */ void *data; } MultiFDRecvParams; diff --git a/migration/options.c b/migration/options.c index 6bbfd4853d..12b1c4dd71 100644 --- a/migration/options.c +++ b/migration/options.c @@ -189,6 +189,7 @@ Property migration_properties[] = { DEFINE_PROP_MIG_CAP("x-block", MIGRATION_CAPABILITY_BLOCK), DEFINE_PROP_MIG_CAP("x-return-path", MIGRATION_CAPABILITY_RETURN_PATH), DEFINE_PROP_MIG_CAP("x-multifd", MIGRATION_CAPABILITY_MULTIFD), + DEFINE_PROP_MIG_CAP("x-main-zero-page", MIGRATION_CAPABILITY_MAIN_ZERO_PAGE), DEFINE_PROP_MIG_CAP("x-background-snapshot", MIGRATION_CAPABILITY_BACKGROUND_SNAPSHOT), #ifdef CONFIG_LINUX @@ -278,6 +279,13 @@ bool migrate_multifd(void) return s->capabilities[MIGRATION_CAPABILITY_MULTIFD]; } +bool migrate_use_main_zero_page(void) +{ + MigrationState *s = migrate_get_current(); + + return s->capabilities[MIGRATION_CAPABILITY_MAIN_ZERO_PAGE]; +} + bool migrate_pause_before_switchover(void) { MigrationState *s = migrate_get_current(); @@ -431,6 +439,7 @@ INITIALIZE_MIGRATE_CAPS_SET(check_caps_background_snapshot, MIGRATION_CAPABILITY_LATE_BLOCK_ACTIVATE, MIGRATION_CAPABILITY_RETURN_PATH, MIGRATION_CAPABILITY_MULTIFD, + MIGRATION_CAPABILITY_MAIN_ZERO_PAGE, MIGRATION_CAPABILITY_PAUSE_BEFORE_SWITCHOVER, MIGRATION_CAPABILITY_AUTO_CONVERGE, MIGRATION_CAPABILITY_RELEASE_RAM, @@ -499,6 +508,9 @@ bool migrate_caps_check(bool *old_caps, bool *new_caps, Error **errp) error_setg(errp, "Postcopy is not yet compatible with multifd"); return false; } + if (new_caps[MIGRATION_CAPABILITY_MAIN_ZERO_PAGE]) { + error_setg(errp, "Postcopy is not yet compatible with main zero copy"); + } } if (new_caps[MIGRATION_CAPABILITY_BACKGROUND_SNAPSHOT]) { diff --git a/migration/options.h b/migration/options.h index 045e2a41a2..c663f637fd 100644 --- a/migration/options.h +++ b/migration/options.h @@ -85,6 +85,7 @@ int migrate_multifd_channels(void); MultiFDCompression migrate_multifd_compression(void); int migrate_multifd_zlib_level(void); int migrate_multifd_zstd_level(void); +bool migrate_use_main_zero_page(void); uint8_t migrate_throttle_trigger_threshold(void); const char *migrate_tls_authz(void); const char *migrate_tls_creds(void); diff --git a/migration/ram.c b/migration/ram.c index 2f5ce4d60b..516b5b9c59 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -1292,7 +1292,6 @@ static int ram_save_multifd_page(QEMUFile *file, RAMBlock *block, if (multifd_queue_page(file, block, offset) < 0) { return -1; } - stat64_add(&mig_stats.normal_pages, 1); return 1; } @@ -2149,17 +2148,43 @@ static int ram_save_target_page_legacy(RAMState *rs, PageSearchStatus *pss) } return res; } - /* - * Do not use multifd in postcopy as one whole host page should be - * placed. Meanwhile postcopy requires atomic update of pages, so even - * if host page size == guest page size the dest guest during run may - * still see partially copied pages which is data corruption. + * Do not use multifd for: + * 1. Compression as the first page in the new block should be posted out + * before sending the compressed page + * 2. In postcopy as one whole host page should be placed */ - if (migrate_multifd() && !migration_in_postcopy()) { + if (!save_page_use_compression(rs) && migrate_multifd() + && !migration_in_postcopy()) { + return ram_save_multifd_page(pss->pss_channel, block, offset); + } + + return ram_save_page(rs, pss); +} + +/** + * ram_save_target_page_multifd: save one target page + * + * Returns the number of pages written + * + * @rs: current RAM state + * @pss: data about the page we want to send + */ +static int ram_save_target_page_multifd(RAMState *rs, PageSearchStatus *pss) +{ + RAMBlock *block = pss->block; + ram_addr_t offset = ((ram_addr_t)pss->page) << TARGET_PAGE_BITS; + int res; + + if (!migration_in_postcopy()) { return ram_save_multifd_page(pss->pss_channel, block, offset); } + res = save_zero_page(pss, pss->pss_channel, block, offset); + if (res > 0) { + return res; + } + return ram_save_page(rs, pss); } @@ -3066,7 +3091,13 @@ static int ram_save_setup(QEMUFile *f, void *opaque) ram_control_after_iterate(f, RAM_CONTROL_SETUP); migration_ops = g_malloc0(sizeof(MigrationOps)); - migration_ops->ram_save_target_page = ram_save_target_page_legacy; + + if (migrate_multifd() && !migrate_use_main_zero_page()) { + migration_ops->ram_save_target_page = ram_save_target_page_multifd; + } else { + migration_ops->ram_save_target_page = ram_save_target_page_legacy; + } + ret = multifd_send_sync_main(f); if (ret < 0) { return ret; diff --git a/migration/trace-events b/migration/trace-events index ee9c8f4d63..3d059f3c06 100644 --- a/migration/trace-events +++ b/migration/trace-events @@ -125,21 +125,21 @@ postcopy_preempt_reset_channel(void) "" # multifd.c multifd_new_send_channel_async(uint8_t id) "channel %u" -multifd_recv(uint8_t id, uint64_t packet_num, uint32_t used, uint32_t flags, uint32_t next_packet_size) "channel %u packet_num %" PRIu64 " pages %u flags 0x%x next packet size %u" +multifd_recv(uint8_t id, uint64_t packet_num, uint32_t normal, uint32_t zero, uint32_t flags, uint32_t next_packet_size) "channel %u packet_num %" PRIu64 " normal pages %u zero pages %u flags 0x%x next packet size %u" multifd_recv_new_channel(uint8_t id) "channel %u" multifd_recv_sync_main(long packet_num) "packet num %ld" multifd_recv_sync_main_signal(uint8_t id) "channel %u" multifd_recv_sync_main_wait(uint8_t id) "channel %u" multifd_recv_terminate_threads(bool error) "error %d" -multifd_recv_thread_end(uint8_t id, uint64_t packets, uint64_t pages) "channel %u packets %" PRIu64 " pages %" PRIu64 +multifd_recv_thread_end(uint8_t id, uint64_t packets, uint64_t normal_pages, uint64_t zero_pages) "channel %u packets %" PRIu64 " normal pages %" PRIu64 " zero pages %" PRIu64 multifd_recv_thread_start(uint8_t id) "%u" -multifd_send(uint8_t id, uint64_t packet_num, uint32_t normal, uint32_t flags, uint32_t next_packet_size) "channel %u packet_num %" PRIu64 " normal pages %u flags 0x%x next packet size %u" +multifd_send(uint8_t id, uint64_t packet_num, uint32_t normalpages, uint32_t zero_pages, uint32_t flags, uint32_t next_packet_size) "channel %u packet_num %" PRIu64 " normal pages %u zero pages %u flags 0x%x next packet size %u" multifd_send_error(uint8_t id) "channel %u" multifd_send_sync_main(long packet_num) "packet num %ld" multifd_send_sync_main_signal(uint8_t id) "channel %u" multifd_send_sync_main_wait(uint8_t id) "channel %u" multifd_send_terminate_threads(bool error) "error %d" -multifd_send_thread_end(uint8_t id, uint64_t packets, uint64_t normal_pages) "channel %u packets %" PRIu64 " normal pages %" PRIu64 +multifd_send_thread_end(uint8_t id, uint64_t packets, uint64_t normal_pages, uint64_t zero_pages) "channel %u packets %" PRIu64 " normal pages %" PRIu64 " zero pages %" PRIu64 multifd_send_thread_start(uint8_t id) "%u" multifd_tls_outgoing_handshake_start(void *ioc, void *tioc, const char *hostname) "ioc=%p tioc=%p hostname=%s" multifd_tls_outgoing_handshake_error(void *ioc, const char *err) "ioc=%p err=%s" diff --git a/qapi/migration.json b/qapi/migration.json index d7dfaa5db9..3a99fe34d8 100644 --- a/qapi/migration.json +++ b/qapi/migration.json @@ -508,6 +508,11 @@ # and should not affect the correctness of postcopy migration. # (since 7.1) # +# @main-zero-page: If enabled, the detection of zero pages will be +# done on the main thread. Otherwise it is done on +# the multifd threads. +# (since 7.1) +# # @switchover-ack: If enabled, migration will not stop the source VM # and complete the migration until an ACK is received from the # destination that it's OK to do so. Exactly when this ACK is @@ -540,7 +545,7 @@ { 'name': 'x-ignore-shared', 'features': [ 'unstable' ] }, 'validate-uuid', 'background-snapshot', 'zero-copy-send', 'postcopy-preempt', 'switchover-ack', - 'dirty-limit'] } + 'dirty-limit', 'main-zero-page'] } ## # @MigrationCapabilityStatus: -- 2.30.2
