what does "flush 253:0" in iotop file on RHEL

Question

I have monitor the IO performance on RHEL via IOTOPs, and I find that there is one process named "flush 253:0" which is the most IO operator.

What does this "flush 253:0" mean? I search in google, not very accurate answer, it seems to be the root path of the system.

Answer 1

It's a kernel process that handles flushing dirty pages (that is your io-writes) from the page cache (that is, your actual file system writes are done asynchronously. This process writes the actual bytes to the drives). See also Cache and TLB Flushing Under Linux.