BUG #12071: Stat collector went crasy (50MB/s constant writes)

The following bug has been logged on the website:

Bug reference: 12071
Logged by: Maxim Boguk
Email address: maxim(dot)boguk(at)gmail(dot)com
PostgreSQL version: 9.2.9
Operating system: Linux
Description:

Hi,

On one of my servers stat collector went crasy on idle system.
It constantly write around 50MB/s on idle database (no activity at all).

What I tried:
1)stop/start the database - no effect
2)update to 9.2.9 from 9.2.7 - no effect

Size of the pgstat.stat file: 5270114 bytes (reasonable small).

strace look like:

open("pg_stat_tmp/pgstat.tmp", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 7
fstat(7, {st_mode=S_IFREG|0600, st_size=0, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0x7f90455b5000
write(7,
"\232\274\245\1fCWw\301\253\1\0\370\27\1\0\0\0\0\0\242\7\0\0\0\0\0\0\211\2569\270"...,
4096) = 4096
write(7,
"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 4096)
= 4096
write(7,
"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0T(at)\340N"..., 4096)
= 4096
write(7,
"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 4096)
= 4096
write(7,
"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 4096)
= 4096
write(7,
"\0\0\0\0\0\2\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 4096)
= 4096
write(7,
"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 4096)
= 4096

I see nothing real weird in strace output.

It's test server with full access so I can try a lot of things but at this
moment I out of ideas.

Kind Regards,
Maksym