Exactly. 2017-04-25 22:40 GMT+08:00 Lei Chang <[email protected]>:
> Good catch. There are a lot of uses of getimeofday for timeout. > > clock_gettime is also affected by NTP if NTP moves time back except > that CLOCK_MONOTONIC > option is used. > > Thanks > Lei > > > On Mon, Apr 24, 2017 at 1:36 PM, Paul Guo <[email protected]> wrote: > > > Hi, > > > > HAWQ sometimes use gettimeofday() syscall for some timeout check in > various > > module, however it could be affected by ntp, so the timeout checking > logic > > could be wrong sometimes. I would propose to use clock_gettime() to > replace > > it on Linux (I have not investigated the alternative on other platforms > > e.g. mac). Both gettimeofday() and clock_gettime() are fast vdso sys call > > so I do not expect there is performance loss in some case where there are > > frequent calls of gettimeofday(). By the way, I found some gettimeofday() > > calls on postgresql and gpdb, so they might have this issue also. > > > > Regards, > > > > Paul > > >
