On 21.1.2015 00:38, Michael Paquier wrote: > On Wed, Jan 21, 2015 at 1:08 AM, Tomas Vondra > >> I've tried to reproduce this on my Raspberry PI 'machine' and it's not >> very difficult to trigger this. About 7 out of 10 'make check' runs fail >> because of 'pgstat wait timeout'. >> >> All the occurences I've seen were right after some sort of VACUUM >> (sometimes plain, sometimes ANALYZE or FREEZE), and the I/O at the time >> looked something like this: >> >> Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s >> avgrq-sz avgqu-sz await r_await w_await svctm %util >> mmcblk0 0.00 75.00 0.00 8.00 0.00 36.00 >> 9.00 5.73 15633.75 0.00 15633.75 125.00 100.00 >> >> So pretty terrible (this is a Class 4 SD card, supposedly able to >> handle 4 MB/s). If hamster had faulty SD card, it might have been >> much worse, I guess. > > By experience, a class 10 is at least necessary, with a minimum > amount of memory to minimize the apparition of those warnings, > hamster having now a 8GB class 10 card.
Well, my goal was exactly to produce those warnings ;-) and see if I can identify some strange cases. That's why I chose just class 4. But even then it produces rather low number of those warnings (one or two per check run), and mostly at the expected places with significant I/O overload. So I'm not any wiser :-( regards Tomas -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers