ps "time" field jumps backward

[Linda Messerschmidt]

Hi all,

For most of 7.2, on up to a 7.3-PRERELEASE built yesterday, I've
noticed that the "time" field reported by ps and top jumps around for
some processes.  I've particularly noticed it with MySQL.

Here are some repeated ps results (ps axo pid,time,wchan,comm) for the
same process over a few minutes:

 1647   0:08.06 ucond  mysqld
 1647   0:08.06 ucond  mysqld
 1647   0:08.06 ucond  mysqld
 1647   0:08.06 ucond  mysqld
 1647   0:08.07 ucond  mysqld
 1647   0:10.24 wdrain mysqld
 1647   0:08.08 ucond  mysqld
 1647   0:09.25 -      mysqld
 1647   0:08.08 ucond  mysqld
 1647   0:08.91 -      mysqld
 1647   0:09.13 wdrain mysqld
 1647   0:09.76 wdrain mysqld
 1647   0:08.10 ucond  mysqld
 1647   0:08.11 ucond  mysqld
 1647   0:08.12 ucond  mysqld
 1647   0:08.12 ucond  mysqld
 1647   0:08.12 ucond  mysqld
 1647   0:08.12 ucond  mysqld
 1647   0:08.38 wdrain mysqld
 1647   0:08.13 ucond  mysqld
 1647   0:09.47 -      mysqld
 1647   0:08.13 ucond  mysqld
 1647   0:08.13 ucond  mysqld

It's like when it starts working it builds up time, but as soon as it
goes back to ucond, it resets back to the earlier value.

This particular machine is an 8-core amd64, but I've seen it on
quad-core i386 as well.

Does anybody have an idea what's going on here?

Thanks for any suggestions!