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migration: Use atomic ops properly for page accountings

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To prepare for thread-safety on page accountings, at least below counters
need to be accessed only atomically, they are:

        ram_counters.transferred
        ram_counters.duplicate
        ram_counters.normal
        ram_counters.postcopy_bytes

There are a lot of other counters but they won't be accessed outside
migration thread, then they're still safe to be accessed without atomic
ops.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Peter Xu 2022-10-11 17:55:51 -04:00 • committed by Juan Quintela
parent f3321554ef
commit 23b7576d78
4 changed files with 51 additions and 23 deletions
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40
migration/ram.c
View file

@ -425,18 +425,25 @@ 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;
void ram_transferred_add(uint64_t bytes)
{
if (runstate_is_running()) {
ram_counters.precopy_bytes += bytes;
} else if (migration_in_postcopy()) {
ram_counters.postcopy_bytes += bytes;
stat64_add(&ram_atomic_counters.postcopy_bytes, bytes);
} else {
ram_counters.downtime_bytes += bytes;
}
ram_counters.transferred += bytes;
stat64_add(&ram_atomic_counters.transferred, bytes);
}
void dirty_sync_missed_zero_copy(void)
@ -725,7 +732,7 @@ 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 = ram_counters.transferred;
rs->bytes_xfer_prev = stat64_get(&ram_atomic_counters.transferred);
}
/**
@ -1085,8 +1092,9 @@ uint64_t ram_pagesize_summary(void)
uint64_t ram_get_total_transferred_pages(void)
{
return ram_counters.normal + ram_counters.duplicate +
compression_counters.pages + xbzrle_counters.pages;
return stat64_get(&ram_atomic_counters.normal) +
stat64_get(&ram_atomic_counters.duplicate) +
compression_counters.pages + xbzrle_counters.pages;
}
static void migration_update_rates(RAMState *rs, int64_t end_time)
@ -1145,8 +1153,8 @@ 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 = ram_counters.transferred - rs->bytes_xfer_prev;
uint64_t bytes_xfer_period =
stat64_get(&ram_atomic_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;
@ -1209,7 +1217,7 @@ 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 = ram_counters.transferred;
rs->bytes_xfer_prev = stat64_get(&ram_atomic_counters.transferred);
}
if (migrate_use_events()) {
qapi_event_send_migration_pass(ram_counters.dirty_sync_count);
@ -1285,7 +1293,7 @@ static int save_zero_page(RAMState *rs, RAMBlock *block, ram_addr_t offset)
int len = save_zero_page_to_file(rs, rs->f, block, offset);
if (len) {
ram_counters.duplicate++;
stat64_add(&ram_atomic_counters.duplicate, 1);
ram_transferred_add(len);
return 1;
}
@ -1322,9 +1330,9 @@ static bool control_save_page(RAMState *rs, RAMBlock *block, ram_addr_t offset,
}
if (bytes_xmit > 0) {
ram_counters.normal++;
stat64_add(&ram_atomic_counters.normal, 1);
} else if (bytes_xmit == 0) {
ram_counters.duplicate++;
stat64_add(&ram_atomic_counters.duplicate, 1);
}
return true;
@ -1354,7 +1362,7 @@ static int save_normal_page(RAMState *rs, RAMBlock *block, ram_addr_t offset,
qemu_put_buffer(rs->f, buf, TARGET_PAGE_SIZE);
}
ram_transferred_add(TARGET_PAGE_SIZE);
ram_counters.normal++;
stat64_add(&ram_atomic_counters.normal, 1);
return 1;
}
@ -1410,7 +1418,7 @@ static int ram_save_multifd_page(RAMState *rs, RAMBlock *block,
if (multifd_queue_page(rs->f, block, offset) < 0) {
return -1;
}
ram_counters.normal++;
stat64_add(&ram_atomic_counters.normal, 1);
return 1;
}
@ -1448,7 +1456,7 @@ update_compress_thread_counts(const CompressParam *param, int bytes_xmit)
ram_transferred_add(bytes_xmit);
if (param->zero_page) {
ram_counters.duplicate++;
stat64_add(&ram_atomic_counters.duplicate, 1);
return;
}
@ -2623,9 +2631,9 @@ void acct_update_position(QEMUFile *f, size_t size, bool zero)
uint64_t pages = size / TARGET_PAGE_SIZE;
if (zero) {
ram_counters.duplicate += pages;
stat64_add(&ram_atomic_counters.duplicate, pages);
} else {
ram_counters.normal += pages;
stat64_add(&ram_atomic_counters.normal, pages);
ram_transferred_add(size);
qemu_file_credit_transfer(f, size);
}