On Mon, Jan 30, 2017 at 10:01 PM, Rushabh Lathia <rushabh.lathia@gmail.com> wrote: > Attached is the patch, which extend the existing wait event infrastructure > to implement the wait events for the disk I/O. Basically pg_stat_activity's > wait event information to show data about disk I/O as well as IPC primitives. > > Implementation details: > > - Added PG_WAIT_IO to pgstat.h and a new enum WaitEventIO > - Added a wait_event_info argument to FileRead, FileWrite, FilePrefetch, > FileWriteback, FileSync, and FileTruncate. Set this wait event just before > performing the file system operation and clear it just after. > - Pass down an appropriate wait event from caller of any of those > functions. > - Also set and clear a wait event around standalone calls to read(), > write(), fsync() in other parts of the system. > - Added documentation for all newly added wait event.
Looks neat, those are unlikely to overlap with other wait events.
Thanks.
> Open issue: > - Might missed few standalone calls to read(), write(), etc which need > to pass the wait_event_info.
It may be an idea to use LD_PRELOAD with custom versions of read(), write() and fsync(), and look at the paths where no flags are set in MyProc->wait_event_info, and log information when that happens.
Yes, may be I will try this.
> Thanks to my colleague Robert Haas for his help in design. > Please let me know your thought, and thanks for reading.
Did you consider a wrapper of the type pg_read_event() or pg_write_event(), etc.?
I thought on that, but eventually stick to this approach as it looks
more neat and uniform with other wait event implementation.