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migration: check for rate_limit_max for RATE_LIMIT_DISABLED

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In migration rate limiting atomic operations are used
to read the rate limit variables and transferred bytes and
they are expensive. Check first if rate_limit_max is equal
to RATE_LIMIT_DISABLED and return false immediately if so.

Note that with this patch we will also will stop flushing
by not calling qemu_fflush() from migration_transferred_bytes()
if the migration rate is not exceeded.
This should be fine since migration thread calls in the loop
migration_update_counters from migration_rate_limit() that
calls the migration_transferred_bytes() and flushes there.

Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011184358.97349-2-elena.ufimtseva@oracle.com>
This commit is contained in:
Elena Ufimtseva 2023-10-11 11:43:55 -07:00 committed by Juan Quintela
parent e4ceec292f
commit 60c7981aa3
1 changed files with 6 additions and 5 deletions
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11
migration/migration-stats.c
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@ -24,14 +24,15 @@ bool migration_rate_exceeded(QEMUFile *f)
return true;
}
uint64_t rate_limit_start = stat64_get(&mig_stats.rate_limit_start);
uint64_t rate_limit_current = migration_transferred_bytes(f);
uint64_t rate_limit_used = rate_limit_current - rate_limit_start;
uint64_t rate_limit_max = stat64_get(&mig_stats.rate_limit_max);
uint64_t rate_limit_max = migration_rate_get();
if (rate_limit_max == RATE_LIMIT_DISABLED) {
return false;
}
uint64_t rate_limit_start = stat64_get(&mig_stats.rate_limit_start);
uint64_t rate_limit_current = migration_transferred_bytes(f);
uint64_t rate_limit_used = rate_limit_current - rate_limit_start;
if (rate_limit_max > 0 && rate_limit_used > rate_limit_max) {
return true;
}