update slow occasionally (1 reply)

to test mysql performance ,i use 1000 robots to update their datas repeatly. I set the long_query_tim to 0 and analysis the result: (the innodb pool size and innodb log/log_buffer size is big enough).innodb_flush_log_at_trx_commit set to 2;
the qps is about 1000 .
question avg time 100us but the max time 200ms, is this because the log flush per second?