My situation is that from time to time a specific process (in this case, it's Thunderbird) doesn't react to user input for a minute or so. I found out using iotop that during this time, it writes quite a lot to the disk, and now I want to find out which file it writes to, but unfortunately iotop gives only stats per process and not per open file(-descriptor).I know that I can use lsof to find out which files the process has currently open, but of course Thunderbird has a lot of them open, so this is not that helpful. iostat only shows statistics per device.The problem occurs only randomly and it might take quite some time for it to appear, so I hope I don't have to strace Thunderbird and wade through long logs to find out which file has the most writes.
How to find out which file is currently written by a process
linux;files;open files
If you attach strace to the process just when it's hung (you can get the pid and queue the command up in advance, in a spare terminal), it'll show the file descriptor of the blocking write.Trivial example:$ mkfifo tmp$ cat /dev/urandom > tmp &[1] 636226  # this will block on open until someone opens for reading$ exec 4<tmp  # now it should be blocked trying to write$ strace -p 636226Process 636226 attached - interrupt to quitwrite(1, L!\f\335\330\27\374\360\212\244c\326\0\356j\374`\310C\30Z\362W\307\365Rv\244?o\225N..., 4096 <unfinished ...>^CProcess 636226 detached