AW: AW: Re[4]: [HACKERS] Allowing WAL fsync to be done via O_SYNC
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. I doubt that setitimer has microsecond precision on HPUX. 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. Not on AIX, and I don't beleive that for the majority of other UNIX platforms eighter. I do however suspect, that some implementations need a busy loop, which would, if at all, only be acceptable on an SMP system. Andreas ---(end of broadcast)--- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])
AW: Re[4]: [HACKERS] 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 real0m10.95s user0m0.40s sys 0m0.74s postgres@s0188000zeu:/usr/postgres time ustest # with 10 us real0m18.62s user0m1.37s sys 0m5.73s Andreas PS: sorry off for weekend now :-) Current looks good on AIX. ustest.c ---(end of broadcast)--- TIP 6: Have you searched our list archives? http://www.postgresql.org/search.mpl
Re: AW: Re[4]: [HACKERS] Allowing WAL fsync to be done via O_SYNC
Zeugswetter Andreas SB [EMAIL PROTECTED] 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 ---(end of broadcast)--- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
