Sorry for delay,
>>I wonder if the prioritisation could be done
>>using nice - each backend is a separate
>>process, so why not to do 'nice(10)' for low
>>priority processes or something like that.
>
>Yes, to a limited degree you can prioritise
>queries using nice and ionice, but it's awkward because:
>
>- All queries run as `postgres' so you can't do per-user limiting very easily
>
>- The postmaster doesn't have a way to set the
>nice level and ionice level when it forks a
>backend, nor does the backend have any way to do
>it later. You can use your own user-defined C functions for this, though.
Postmaster hasn't a way to modify the system nice
or ionice, but it can send signals to child
process. Sending a user signal to sleep
completely the child (i/o and cpu) or before any
i/o call can do the trick. Perhaps it's time to
add a query scheduler or a more complete/complex one in postgres.
>--
>Craig Ringer
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