On 12/08/2011 08:53 PM, Tomas Vondra wrote:
On 8 Prosinec 2011, 12:24, Craig Ringer wrote:
- admission control, queuing and resource limiting to optimally load a
machine. Some limited level is possible with external pooling, but only by
limiting concurrent workers.
o d
The first thing I'd like to see is "user profiles"z- being able to set
things like work_mem, synchronous_commit, etc. on per-user basis
separately.
You can.
ALTER USER username SET work_mem = '100MB';
It's not a hard cap - the user can raise/lower it however they like. The
initial value can be set globally, per-user, per-database, or globally.
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.
- Most importantly, even if you nice and ionice using C functions or
manually with the cmdline utilities, you can't affect the bgwriter, nor
can you affect how much data a low-priority query pushes out of cache.
--
Craig Ringer
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