Re: [PATCH 1/3] migration: Merge ram_counters and ram_atomic_counters

[David Edmondson]

On Wednesday, 2023-03-01 at 13:40:24 +01, Juan Quintela wrote:
> Using MgrationStats as type for ram_counters mean that we didn't have
> to re-declare each value in another struct. The need of atomic
> counters have make us to create MigrationAtomicStats for this atomic
> counters.
>
> Create RAMStats type which is a merge of MigrationStats and
> MigrationAtomicStats removing unused members.
>
> Signed-off-by: Juan Quintela <quintela@redhat.com>
> ---
>  migration/ram.h       | 26 ++++++++++++++------------
>  migration/migration.c |  8 ++++----
>  migration/multifd.c   |  4 ++--
>  migration/ram.c       | 39 ++++++++++++++++-----------------------
>  4 files changed, 36 insertions(+), 41 deletions(-)
>
> diff --git a/migration/ram.h b/migration/ram.h
> index 81cbb0947c..ca9adcb2ad 100644
> --- a/migration/ram.h
> +++ b/migration/ram.h
> @@ -35,25 +35,27 @@
>  #include "qemu/stats64.h"
>  
>  /*
> - * These are the migration statistic counters that need to be updated using
> - * atomic ops (can be accessed by more than one thread).  Here since we
> - * cannot modify MigrationStats directly to use Stat64 as it was defined in
> - * the QAPI scheme, we define an internal structure to hold them, and we
> - * propagate the real values when QMP queries happen.
> - *
> - * IOW, the corresponding fields within ram_counters on these specific
> - * fields will be always zero and not being used at all; they're just
> - * placeholders to make it QAPI-compatible.
> + * These are the ram migration statistic counters.  It is lousely

s/lousely/loosely/

> + * based on MigrationStats.  We change to Stat64 any counter that need

s/need/needs/

> + * to be updated using atomic ops (can be accessed by more than one
> + * thread).
>   */
>  typedef struct {
>      Stat64 transferred;
>      Stat64 duplicate;
>      Stat64 normal;
>      Stat64 postcopy_bytes;
> -} MigrationAtomicStats;
> +    int64_t remaining;
> +    int64_t dirty_pages_rate;
> +    int64_t dirty_sync_count;
> +    int64_t postcopy_requests;
> +    uint64_t multifd_bytes;
> +    uint64_t precopy_bytes;
> +    uint64_t downtime_bytes;
> +    uint64_t dirty_sync_missed_zero_copy;
> +} RAMStats;
>  
> -extern MigrationAtomicStats ram_atomic_counters;
> -extern MigrationStats ram_counters;
> +extern RAMStats ram_counters;
>  extern XBZRLECacheStats xbzrle_counters;
>  extern CompressionStats compression_counters;
>  
> diff --git a/migration/migration.c b/migration/migration.c
> index ae2025d9d8..923f4762f4 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -1140,12 +1140,12 @@ static void populate_ram_info(MigrationInfo *info, 
> MigrationState *s)
>      size_t page_size = qemu_target_page_size();
>  
>      info->ram = g_malloc0(sizeof(*info->ram));
> -    info->ram->transferred = stat64_get(&ram_atomic_counters.transferred);
> +    info->ram->transferred = stat64_get(&ram_counters.transferred);
>      info->ram->total = ram_bytes_total();
> -    info->ram->duplicate = stat64_get(&ram_atomic_counters.duplicate);
> +    info->ram->duplicate = stat64_get(&ram_counters.duplicate);
>      /* legacy value.  It is not used anymore */
>      info->ram->skipped = 0;
> -    info->ram->normal = stat64_get(&ram_atomic_counters.normal);
> +    info->ram->normal = stat64_get(&ram_counters.normal);
>      info->ram->normal_bytes = info->ram->normal * page_size;
>      info->ram->mbps = s->mbps;
>      info->ram->dirty_sync_count = ram_counters.dirty_sync_count;
> @@ -1157,7 +1157,7 @@ static void populate_ram_info(MigrationInfo *info, 
> MigrationState *s)
>      info->ram->pages_per_second = s->pages_per_second;
>      info->ram->precopy_bytes = ram_counters.precopy_bytes;
>      info->ram->downtime_bytes = ram_counters.downtime_bytes;
> -    info->ram->postcopy_bytes = 
> stat64_get(&ram_atomic_counters.postcopy_bytes);
> +    info->ram->postcopy_bytes = stat64_get(&ram_counters.postcopy_bytes);
>  
>      if (migrate_use_xbzrle()) {
>          info->xbzrle_cache = g_malloc0(sizeof(*info->xbzrle_cache));
> diff --git a/migration/multifd.c b/migration/multifd.c
> index 5e85c3ea9b..7cb2326d03 100644
> --- a/migration/multifd.c
> +++ b/migration/multifd.c
> @@ -433,7 +433,7 @@ static int multifd_send_pages(QEMUFile *f)
>      transferred = ((uint64_t) pages->num) * p->page_size + p->packet_len;
>      qemu_file_acct_rate_limit(f, transferred);
>      ram_counters.multifd_bytes += transferred;
> -    stat64_add(&ram_atomic_counters.transferred, transferred);
> +    stat64_add(&ram_counters.transferred, transferred);
>      qemu_mutex_unlock(&p->mutex);
>      qemu_sem_post(&p->sem);
>  
> @@ -628,7 +628,7 @@ int multifd_send_sync_main(QEMUFile *f)
>          p->pending_job++;
>          qemu_file_acct_rate_limit(f, p->packet_len);
>          ram_counters.multifd_bytes += p->packet_len;
> -        stat64_add(&ram_atomic_counters.transferred, p->packet_len);
> +        stat64_add(&ram_counters.transferred, p->packet_len);
>          qemu_mutex_unlock(&p->mutex);
>          qemu_sem_post(&p->sem);
>      }
> diff --git a/migration/ram.c b/migration/ram.c
> index 96e8a19a58..9c2151307d 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -458,25 +458,18 @@ uint64_t ram_bytes_remaining(void)
>                         0;
>  }
>  
> -/*
> - * NOTE: not all stats in ram_counters are used in reality.  See comments
> - * for struct MigrationAtomicStats.  The ultimate result of ram migration
> - * counters will be a merged version with both ram_counters and the atomic
> - * fields in ram_atomic_counters.
> - */
> -MigrationStats ram_counters;
> -MigrationAtomicStats ram_atomic_counters;
> +RAMStats ram_counters;
>  
>  void ram_transferred_add(uint64_t bytes)
>  {
>      if (runstate_is_running()) {
>          ram_counters.precopy_bytes += bytes;
>      } else if (migration_in_postcopy()) {
> -        stat64_add(&ram_atomic_counters.postcopy_bytes, bytes);
> +        stat64_add(&ram_counters.postcopy_bytes, bytes);
>      } else {
>          ram_counters.downtime_bytes += bytes;
>      }
> -    stat64_add(&ram_atomic_counters.transferred, bytes);
> +    stat64_add(&ram_counters.transferred, bytes);
>  }
>  
>  void dirty_sync_missed_zero_copy(void)
> @@ -757,7 +750,7 @@ void mig_throttle_counter_reset(void)
>  
>      rs->time_last_bitmap_sync = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
>      rs->num_dirty_pages_period = 0;
> -    rs->bytes_xfer_prev = stat64_get(&ram_atomic_counters.transferred);
> +    rs->bytes_xfer_prev = stat64_get(&ram_counters.transferred);
>  }
>  
>  /**
> @@ -1131,8 +1124,8 @@ uint64_t ram_pagesize_summary(void)
>  
>  uint64_t ram_get_total_transferred_pages(void)
>  {
> -    return  stat64_get(&ram_atomic_counters.normal) +
> -        stat64_get(&ram_atomic_counters.duplicate) +
> +    return  stat64_get(&ram_counters.normal) +

Extra space after "return"? (Not yours, but 🤷.)

> +        stat64_get(&ram_counters.duplicate) +
>          compression_counters.pages + xbzrle_counters.pages;
>  }
>  
> @@ -1193,7 +1186,7 @@ static void migration_trigger_throttle(RAMState *rs)
>      MigrationState *s = migrate_get_current();
>      uint64_t threshold = s->parameters.throttle_trigger_threshold;
>      uint64_t bytes_xfer_period =
> -        stat64_get(&ram_atomic_counters.transferred) - rs->bytes_xfer_prev;
> +        stat64_get(&ram_counters.transferred) - rs->bytes_xfer_prev;
>      uint64_t bytes_dirty_period = rs->num_dirty_pages_period * 
> TARGET_PAGE_SIZE;
>      uint64_t bytes_dirty_threshold = bytes_xfer_period * threshold / 100;
>  
> @@ -1256,7 +1249,7 @@ static void migration_bitmap_sync(RAMState *rs)
>          /* reset period counters */
>          rs->time_last_bitmap_sync = end_time;
>          rs->num_dirty_pages_period = 0;
> -        rs->bytes_xfer_prev = stat64_get(&ram_atomic_counters.transferred);
> +        rs->bytes_xfer_prev = stat64_get(&ram_counters.transferred);
>      }
>      if (migrate_use_events()) {
>          qapi_event_send_migration_pass(ram_counters.dirty_sync_count);
> @@ -1333,7 +1326,7 @@ static int save_zero_page(PageSearchStatus *pss, 
> RAMBlock *block,
>      int len = save_zero_page_to_file(pss, block, offset);
>  
>      if (len) {
> -        stat64_add(&ram_atomic_counters.duplicate, 1);
> +        stat64_add(&ram_counters.duplicate, 1);
>          ram_transferred_add(len);
>          return 1;
>      }
> @@ -1370,9 +1363,9 @@ static bool control_save_page(PageSearchStatus *pss, 
> RAMBlock *block,
>      }
>  
>      if (bytes_xmit > 0) {
> -        stat64_add(&ram_atomic_counters.normal, 1);
> +        stat64_add(&ram_counters.normal, 1);
>      } else if (bytes_xmit == 0) {
> -        stat64_add(&ram_atomic_counters.duplicate, 1);
> +        stat64_add(&ram_counters.duplicate, 1);
>      }
>  
>      return true;
> @@ -1404,7 +1397,7 @@ static int save_normal_page(PageSearchStatus *pss, 
> RAMBlock *block,
>          qemu_put_buffer(file, buf, TARGET_PAGE_SIZE);
>      }
>      ram_transferred_add(TARGET_PAGE_SIZE);
> -    stat64_add(&ram_atomic_counters.normal, 1);
> +    stat64_add(&ram_counters.normal, 1);
>      return 1;
>  }
>  
> @@ -1460,7 +1453,7 @@ static int ram_save_multifd_page(QEMUFile *file, 
> RAMBlock *block,
>      if (multifd_queue_page(file, block, offset) < 0) {
>          return -1;
>      }
> -    stat64_add(&ram_atomic_counters.normal, 1);
> +    stat64_add(&ram_counters.normal, 1);
>  
>      return 1;
>  }
> @@ -1499,7 +1492,7 @@ update_compress_thread_counts(const CompressParam 
> *param, int bytes_xmit)
>      ram_transferred_add(bytes_xmit);
>  
>      if (param->zero_page) {
> -        stat64_add(&ram_atomic_counters.duplicate, 1);
> +        stat64_add(&ram_counters.duplicate, 1);
>          return;
>      }
>  
> @@ -2634,9 +2627,9 @@ void acct_update_position(QEMUFile *f, size_t size, 
> bool zero)
>      uint64_t pages = size / TARGET_PAGE_SIZE;
>  
>      if (zero) {
> -        stat64_add(&ram_atomic_counters.duplicate, pages);
> +        stat64_add(&ram_counters.duplicate, pages);
>      } else {
> -        stat64_add(&ram_atomic_counters.normal, pages);
> +        stat64_add(&ram_counters.normal, pages);
>          ram_transferred_add(size);
>          qemu_file_credit_transfer(f, size);
>      }
-- 
And you're standing here beside me, I love the passing of time.