* Juan Quintela (quint...@redhat.com) wrote:
> We synchronize all threads each RAM_SAVE_FLAG_EOS. Bitmap
> synchronizations don't happen inside a ram section, so we are safe
> about two channels trying to overwrite the same memory.
>
> Signed-off-by: Juan Quintela <quint...@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> --
> seq needs to be atomic now, will also be accessed from main thread.
> Fix the if (true || ...) leftover
> ---
> migration/ram.c | 147 ++++++++++++++++++++++++++++++++---------
> migration/trace-events | 6 ++
> 2 files changed, 122 insertions(+), 31 deletions(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index 793f0dc5d3..516f347d24 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -510,6 +510,8 @@ exit:
> #define MULTIFD_MAGIC 0x11223344U
> #define MULTIFD_VERSION 1
>
> +#define MULTIFD_FLAG_SYNC (1 << 0)
> +
> typedef struct {
> uint32_t magic;
> uint32_t version;
> @@ -577,6 +579,8 @@ typedef struct {
> uint32_t num_packets;
> /* pages sent through this channel */
> uint32_t num_pages;
> + /* syncs main thread and channels */
> + QemuSemaphore sem_sync;
> } MultiFDSendParams;
>
> typedef struct {
> @@ -614,6 +618,8 @@ typedef struct {
> uint32_t num_packets;
> /* pages sent through this channel */
> uint32_t num_pages;
> + /* syncs main thread and channels */
> + QemuSemaphore sem_sync;
> } MultiFDRecvParams;
>
> static int multifd_send_initial_packet(MultiFDSendParams *p, Error **errp)
> @@ -801,6 +807,10 @@ struct {
> int count;
> /* array of pages to sent */
> MultiFDPages_t *pages;
> + /* syncs main thread and channels */
> + QemuSemaphore sem_sync;
> + /* global number of generated multifd packets */
> + uint64_t packet_num;
> } *multifd_send_state;
>
> static void multifd_send_terminate_threads(Error *err)
> @@ -848,6 +858,7 @@ int multifd_save_cleanup(Error **errp)
> p->c = NULL;
> qemu_mutex_destroy(&p->mutex);
> qemu_sem_destroy(&p->sem);
> + qemu_sem_destroy(&p->sem_sync);
> g_free(p->name);
> p->name = NULL;
> multifd_pages_clear(p->pages);
> @@ -856,6 +867,7 @@ int multifd_save_cleanup(Error **errp)
> g_free(p->packet);
> p->packet = NULL;
> }
> + qemu_sem_destroy(&multifd_send_state->sem_sync);
> g_free(multifd_send_state->params);
> multifd_send_state->params = NULL;
> multifd_pages_clear(multifd_send_state->pages);
> @@ -865,6 +877,33 @@ int multifd_save_cleanup(Error **errp)
> return ret;
> }
>
> +static void multifd_send_sync_main(void)
> +{
> + int i;
> +
> + if (!migrate_use_multifd()) {
> + return;
> + }
> + for (i = 0; i < migrate_multifd_channels(); i++) {
> + MultiFDSendParams *p = &multifd_send_state->params[i];
> +
> + trace_multifd_send_sync_main_signal(p->id);
> +
> + qemu_mutex_lock(&p->mutex);
> + p->flags |= MULTIFD_FLAG_SYNC;
> + p->pending_job++;
> + qemu_mutex_unlock(&p->mutex);
> + qemu_sem_post(&p->sem);
> + }
> + for (i = 0; i < migrate_multifd_channels(); i++) {
> + MultiFDSendParams *p = &multifd_send_state->params[i];
> +
> + trace_multifd_send_sync_main_wait(p->id);
> + qemu_sem_wait(&multifd_send_state->sem_sync);
> + }
> +
> trace_multifd_send_sync_main(atomic_read(&multifd_send_state->packet_num));
> +}
> +
> static void *multifd_send_thread(void *opaque)
> {
> MultiFDSendParams *p = opaque;
> @@ -901,15 +940,17 @@ static void *multifd_send_thread(void *opaque)
> qemu_mutex_lock(&p->mutex);
> p->pending_job--;
> qemu_mutex_unlock(&p->mutex);
> - continue;
> +
> + if (flags & MULTIFD_FLAG_SYNC) {
> + qemu_sem_post(&multifd_send_state->sem_sync);
> + }
> } else if (p->quit) {
> qemu_mutex_unlock(&p->mutex);
> break;
> + } else {
> + qemu_mutex_unlock(&p->mutex);
> + /* sometimes there are spurious wakeups */
> }
> - qemu_mutex_unlock(&p->mutex);
> - /* this is impossible */
> - error_setg(&local_err, "multifd_send_thread: Unknown command");
> - break;
> }
>
> out:
> @@ -961,12 +1002,14 @@ int multifd_save_setup(void)
> multifd_send_state->params = g_new0(MultiFDSendParams, thread_count);
> atomic_set(&multifd_send_state->count, 0);
> multifd_send_state->pages = multifd_pages_init(page_count);
> + qemu_sem_init(&multifd_send_state->sem_sync, 0);
>
> for (i = 0; i < thread_count; i++) {
> MultiFDSendParams *p = &multifd_send_state->params[i];
>
> qemu_mutex_init(&p->mutex);
> qemu_sem_init(&p->sem, 0);
> + qemu_sem_init(&p->sem_sync, 0);
> p->quit = false;
> p->pending_job = 0;
> p->id = i;
> @@ -991,6 +1034,10 @@ struct {
> MultiFDRecvParams *params;
> /* number of created threads */
> int count;
> + /* syncs main thread and channels */
> + QemuSemaphore sem_sync;
> + /* global number of generated multifd packets */
> + uint64_t packet_num;
> } *multifd_recv_state;
>
> static void multifd_recv_terminate_threads(Error *err)
> @@ -1036,6 +1083,7 @@ int multifd_load_cleanup(Error **errp)
> p->c = NULL;
> qemu_mutex_destroy(&p->mutex);
> qemu_sem_destroy(&p->sem);
> + qemu_sem_destroy(&p->sem_sync);
> g_free(p->name);
> p->name = NULL;
> multifd_pages_clear(p->pages);
> @@ -1044,6 +1092,7 @@ int multifd_load_cleanup(Error **errp)
> g_free(p->packet);
> p->packet = NULL;
> }
> + qemu_sem_destroy(&multifd_recv_state->sem_sync);
> g_free(multifd_recv_state->params);
> multifd_recv_state->params = NULL;
> g_free(multifd_recv_state);
> @@ -1052,6 +1101,42 @@ int multifd_load_cleanup(Error **errp)
> return ret;
> }
>
> +static void multifd_recv_sync_main(void)
> +{
> + int i;
> +
> + if (!migrate_use_multifd()) {
> + return;
> + }
> + for (i = 0; i < migrate_multifd_channels(); i++) {
> + MultiFDRecvParams *p = &multifd_recv_state->params[i];
> +
> + trace_multifd_recv_sync_main_signal(p->id);
> + qemu_mutex_lock(&p->mutex);
> + p->pending_job = true;
> + qemu_mutex_unlock(&p->mutex);
> + }
> + for (i = 0; i < migrate_multifd_channels(); i++) {
> + MultiFDRecvParams *p = &multifd_recv_state->params[i];
> +
> + trace_multifd_recv_sync_main_wait(p->id);
> + qemu_sem_wait(&multifd_recv_state->sem_sync);
> + qemu_mutex_lock(&p->mutex);
> + if (atomic_read(&multifd_recv_state->packet_num) < p->packet_num) {
> + atomic_set(&multifd_recv_state->packet_num, p->packet_num);
> + }
> + qemu_mutex_unlock(&p->mutex);
> + }
> + for (i = 0; i < migrate_multifd_channels(); i++) {
> + MultiFDRecvParams *p = &multifd_recv_state->params[i];
> +
> + trace_multifd_recv_sync_main_signal(p->id);
> +
> + qemu_sem_post(&p->sem_sync);
> + }
> +
> trace_multifd_recv_sync_main(atomic_read(&multifd_recv_state->packet_num));
> +}
> +
> static void *multifd_recv_thread(void *opaque)
> {
> MultiFDRecvParams *p = opaque;
> @@ -1061,37 +1146,30 @@ static void *multifd_recv_thread(void *opaque)
> trace_multifd_recv_thread_start(p->id);
>
> while (true) {
> - qemu_sem_wait(&p->sem);
> + uint32_t used;
> + uint32_t flags;
> +
> + /* ToDo: recv packet here */
> +
> qemu_mutex_lock(&p->mutex);
> - if (p->pending_job) {
> - uint32_t used;
> - uint32_t flags;
> - qemu_mutex_unlock(&p->mutex);
> -
> - /* ToDo: recv packet here */
> -
> - qemu_mutex_lock(&p->mutex);
> - ret = multifd_recv_unfill_packet(p, &local_err);
> - if (ret) {
> - qemu_mutex_unlock(&p->mutex);
> - break;
> - }
> -
> - used = p->pages->used;
> - flags = p->flags;
> - trace_multifd_recv(p->id, p->packet_num, used, flags);
> - p->pending_job = false;
> - p->num_packets++;
> - p->num_pages += used;
> - qemu_mutex_unlock(&p->mutex);
> - } else if (p->quit) {
> + ret = multifd_recv_unfill_packet(p, &local_err);
> + if (ret) {
> qemu_mutex_unlock(&p->mutex);
> break;
> }
> +
> + used = p->pages->used;
> + flags = p->flags;
> + trace_multifd_recv(p->id, p->packet_num, used, flags);
> + p->pending_job = false;
> + p->num_packets++;
> + p->num_pages += used;
> qemu_mutex_unlock(&p->mutex);
> - /* this is impossible */
> - error_setg(&local_err, "multifd_recv_thread: Unknown command");
> - break;
> +
> + if (flags & MULTIFD_FLAG_SYNC) {
> + qemu_sem_post(&multifd_recv_state->sem_sync);
> + qemu_sem_wait(&p->sem_sync);
> + }
> }
>
> if (local_err) {
> @@ -1119,12 +1197,14 @@ int multifd_load_setup(void)
> multifd_recv_state = g_malloc0(sizeof(*multifd_recv_state));
> multifd_recv_state->params = g_new0(MultiFDRecvParams, thread_count);
> atomic_set(&multifd_recv_state->count, 0);
> + qemu_sem_init(&multifd_recv_state->sem_sync, 0);
>
> for (i = 0; i < thread_count; i++) {
> MultiFDRecvParams *p = &multifd_recv_state->params[i];
>
> qemu_mutex_init(&p->mutex);
> qemu_sem_init(&p->sem, 0);
> + qemu_sem_init(&p->sem_sync, 0);
> p->quit = false;
> p->pending_job = false;
> p->id = i;
> @@ -2882,6 +2962,7 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
> ram_control_before_iterate(f, RAM_CONTROL_SETUP);
> ram_control_after_iterate(f, RAM_CONTROL_SETUP);
>
> + multifd_send_sync_main();
> qemu_put_be64(f, RAM_SAVE_FLAG_EOS);
>
> return 0;
> @@ -2962,6 +3043,7 @@ static int ram_save_iterate(QEMUFile *f, void *opaque)
> */
> ram_control_after_iterate(f, RAM_CONTROL_ROUND);
>
> + multifd_send_sync_main();
> out:
> qemu_put_be64(f, RAM_SAVE_FLAG_EOS);
> ram_counters.transferred += 8;
> @@ -3015,6 +3097,7 @@ static int ram_save_complete(QEMUFile *f, void *opaque)
>
> rcu_read_unlock();
>
> + multifd_send_sync_main();
> qemu_put_be64(f, RAM_SAVE_FLAG_EOS);
>
> return 0;
> @@ -3504,6 +3587,7 @@ static int ram_load_postcopy(QEMUFile *f)
> break;
> case RAM_SAVE_FLAG_EOS:
> /* normal exit */
> + multifd_recv_sync_main();
> break;
> default:
> error_report("Unknown combination of migration flags: %#x"
> @@ -3692,6 +3776,7 @@ static int ram_load(QEMUFile *f, void *opaque, int
> version_id)
> break;
> case RAM_SAVE_FLAG_EOS:
> /* normal exit */
> + multifd_recv_sync_main();
> break;
> default:
> if (flags & RAM_SAVE_FLAG_HOOK) {
> diff --git a/migration/trace-events b/migration/trace-events
> index c667d98529..ea39bb2bc5 100644
> --- a/migration/trace-events
> +++ b/migration/trace-events
> @@ -77,9 +77,15 @@ migration_bitmap_sync_start(void) ""
> migration_bitmap_sync_end(uint64_t dirty_pages) "dirty_pages %" PRIu64
> migration_throttle(void) ""
> multifd_recv(uint8_t id, uint64_t packet_num, uint32_t used, uint32_t flags)
> "channel %d packet number %ld pages %d flags 0x%x"
> +multifd_recv_sync_main(uint32_t seq) "seq %d"
> +multifd_recv_sync_main_signal(uint8_t id) "channel %d"
> +multifd_recv_sync_main_wait(uint8_t id) "channel %d"
> multifd_recv_thread_end(uint8_t id, uint32_t packets, uint32_t pages)
> "channel %d packets %d pages %d"
> multifd_recv_thread_start(uint8_t id) "%d"
> multifd_send(uint8_t id, uint64_t packet_num, uint32_t used, uint32_t flags)
> "channel %d packet_num %ld pages %d flags 0x%x"
> +multifd_send_sync_main(uint32_t seq) "seq %d"
> +multifd_send_sync_main_signal(uint8_t id) "channel %d"
> +multifd_send_sync_main_wait(uint8_t id) "channel %d"
> multifd_send_thread_end(uint8_t id, uint32_t packets, uint32_t pages)
> "channel %d packets %d pages %d"
> multifd_send_thread_start(uint8_t id) "%d"
> ram_discard_range(const char *rbname, uint64_t start, size_t len) "%s:
> start: %" PRIx64 " %zx"
> --
> 2.17.1
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
