Re: [PATCH v7 10/12] multifd: Support for zero pages transmission

[Leonardo Brás]

On Tue, 2022-08-02 at 08:39 +0200, Juan Quintela wrote:
> This patch adds counters and similar.  Logic will be added on the
> following patch.
> 
> Signed-off-by: Juan Quintela <quintela@redhat.com>
> 
> ---
> 
> Added counters for duplicated/non duplicated pages.
> Removed reviewed by from David.
> Add total_zero_pages
> ---
>  migration/multifd.h    | 17 ++++++++++++++++-
>  migration/multifd.c    | 36 +++++++++++++++++++++++++++++-------
>  migration/ram.c        |  2 --
>  migration/trace-events |  8 ++++----
>  4 files changed, 49 insertions(+), 14 deletions(-)
> 
> diff --git a/migration/multifd.h b/migration/multifd.h
> index cd389d18d2..a1b852200d 100644
> --- a/migration/multifd.h
> +++ b/migration/multifd.h
> @@ -47,7 +47,10 @@ 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;
> @@ -127,6 +130,8 @@ typedef struct {
>      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 */
> @@ -135,6 +140,10 @@ 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;

More of an organization viewpoint: 
I can't see total_zero_pages, zero[] and zero_num as Multifd "Parameters". 
But OTOH there are other data like this in the struct for keeping migration
status, so not an issue.

>      /* used for compression methods */
>      void *data;
>  }  MultiFDSendParams;
> @@ -184,12 +193,18 @@ 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/multifd.c b/migration/multifd.c
> index 68fc9f8e88..4473d9f834 100644
> --- a/migration/multifd.c
> +++ b/migration/multifd.c
> @@ -263,6 +263,7 @@ 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);
> @@ -323,7 +324,15 @@ 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;
>      }
>  
> @@ -432,6 +441,8 @@ static int multifd_send_pages(QEMUFile *f)
>      ram_counters.multifd_bytes += p->sent_bytes;
>      qemu_file_acct_rate_limit(f, p->sent_bytes);
>      p->sent_bytes = 0;
> +    ram_counters.normal += p->normal_num;
> +    ram_counters.duplicate += p->zero_num;
>      qemu_mutex_unlock(&p->mutex);
>      qemu_sem_post(&p->sem);
>  
> @@ -545,6 +556,8 @@ 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);
> @@ -666,6 +679,7 @@ static void *multifd_send_thread(void *opaque)
>              qemu_mutex_unlock(&p->mutex);
>  
>              p->normal_num = 0;
> +            p->zero_num = 0;
>  
>              if (use_zero_copy_send) {
>                  p->iovs_num = 0;
> @@ -687,8 +701,8 @@ static void *multifd_send_thread(void *opaque)
>              }
>              multifd_send_fill_packet(p);
>  
> -            trace_multifd_send(p->id, packet_num, p->normal_num, p->flags,
> -                               p->next_packet_size);
> +            trace_multifd_send(p->id, packet_num, p->normal_num, p->zero_num,
> +                               p->flags, p->next_packet_size);
>  
>              if (use_zero_copy_send) {
>                  /* Send header first, without zerocopy */
> @@ -712,6 +726,7 @@ static void *multifd_send_thread(void *opaque)
>              qemu_mutex_lock(&p->mutex);
>              p->num_packets++;
>              p->total_normal_pages += p->normal_num;
> +            p->total_zero_pages += p->zero_num;

I can see it getting declared, incremented and used. But where is it initialized
in zero? I mean, should it not have 'p->total_normal_pages = 0;' somewhere in
setup?

(I understand multifd_save_setup() allocates a multifd_send_state->params with
g_new0(),but other variables are zeroed there, like p->pending_job and 
p->write_flags, so why not?)   

>              p->pages->num = 0;
>              p->pages->block = NULL;
>              p->sent_bytes += p->packet_len;;
> @@ -753,7 +768,8 @@ out:
>      qemu_mutex_unlock(&p->mutex);
>  
>      rcu_unregister_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;
>  }
> @@ -938,6 +954,7 @@ 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_use_zero_copy_send()) {
>              p->write_flags = QIO_CHANNEL_WRITE_FLAG_ZERO_COPY;
> @@ -1046,6 +1063,8 @@ int multifd_load_cleanup(Error **errp)
>          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);
> @@ -1116,13 +1135,14 @@ static void *multifd_recv_thread(void *opaque)
>              break;
>          }
>  
> -        trace_multifd_recv(p->id, p->packet_num, p->normal_num, p->flags,
> -                           p->next_packet_size);
> +        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;
>          p->num_packets++;
>          p->total_normal_pages += p->normal_num;
> +        p->total_normal_pages += p->zero_num;
>          qemu_mutex_unlock(&p->mutex);
>  
>          if (p->normal_num) {
> @@ -1147,7 +1167,8 @@ 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;
>  }
> @@ -1187,6 +1208,7 @@ 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/ram.c b/migration/ram.c
> index 291ba5c0ed..2af70f517a 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -1412,8 +1412,6 @@ static int ram_save_multifd_page(RAMState *rs, RAMBlock 
> *block,
>      if (multifd_queue_page(rs->f, block, offset) < 0) {
>          return -1;
>      }
> -    ram_counters.normal++;
> -
>      return 1;
>  }
>  
> diff --git a/migration/trace-events b/migration/trace-events
> index a34afe7b85..d34aec177c 100644
> --- a/migration/trace-events
> +++ b/migration/trace-events
> @@ -120,21 +120,21 @@ 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"