On Mon, Jan 06, 2020 at 02:13:40PM +0800, Qu Wenruo wrote: > The execution time of this per-profile calculation is a little below > 20 us per 5 iterations in my test VM. > Although all such calculation will need to acquire chunk mutex, the > impact should be small enough. The problem is not only the execution time of statfs, but what happens when them mutex is contended. This was the problem with the block group mutex in the past that had to be converted to RCU. If the chunk mutex gets locked because a new chunk is allocated, until it finishes then statfs will block. The time can vary a lot depending on the workload and delay in seconds can trigger system monitors alert.
