Обсуждение: AW: Re[4]: Allowing WAL fsync to be done via O_SYNC

> >> definitely need before considering this is to replace the existing
> >> spinlock mechanism with something more efficient.
> 
> > What sort of problems are you seeing with the spinlock code?
> 
> It's great as long as you never block, but it sucks for making things

I like optimistic approaches :-)

> wait, because the wait interval will be some multiple of 10 msec rather
> than just the time till the lock comes free.

On the AIX platform usleep (3) is able to really sleep microseconds without 
busying the cpu when called for more than approx. 100 us (the longer the interval,
the less busy the cpu gets) .
Would this not be ideal for spin_lock, or is usleep not very common ?
Linux sais it is in the BSD 4.3 standard.

postgres@s0188000zeu:/usr/postgres> time ustest # with 100 us
real    0m10.95s
user    0m0.40s
sys     0m0.74s

postgres@s0188000zeu:/usr/postgres> time ustest # with 10 us
real    0m18.62s
user    0m1.37s
sys     0m5.73s

Andreas

PS: sorry off for weekend now :-) Current looks good on AIX.

Zeugswetter Andreas SB  <ZeugswetterA@wien.spardat.at> writes:
>> It's great as long as you never block, but it sucks for making things
>> wait, because the wait interval will be some multiple of 10 msec rather
>> than just the time till the lock comes free.

> On the AIX platform usleep (3) is able to really sleep microseconds without 
> busying the cpu when called for more than approx. 100 us (the longer the interval,
> the less busy the cpu gets) .
> Would this not be ideal for spin_lock, or is usleep not very common ?
> Linux sais it is in the BSD 4.3 standard.

HPUX has usleep, but the man page says
    The usleep() function is included for its historical usage. The    setitimer() function is preferred over this
function.

In any case, I would expect that all these functions offer accuracy
no better than the scheduler's regular clock cycle (~ 100Hz) on most
kernels.
        regards, tom lane