> Hi!
>
> > > Simple task might be 'memory priorities'. Something like priorities
> > > for scheduler but for memory. (I tried to implement them, and they
> > > gave <1% performance gain ;-), but I have interface to set such
> > > parameter if you want to play).
> >
> > sounds rather good... (swapout-priorities??)
>
> But proved to be pretty ineffective. I came to this idea when I
> realized that to cook machine, running 100 processes will not hurt too
> much. But running 10 processes, 50 megabytes each will cook almost
> anything...
I think it will be more of a scheduling issue...
Suspending low-priority, background jobs for a minute
(in turn) will make swapping / running possible again
(even without changes to the swapping code).
To do this, we could create a new scheduling class: SCHED_BG
Processes in this class are run:
- one at a time (possibly two??)
- for LONG slices, getting longer after each slice (a'la CTSS)
- so only one of them has to be in memory...
- at a lower priority than interactive jobs.
- CPU time and memory used by these processes aren't charged
when user quota's are inforced... this should encourage users
to run large jobs (and even medium compiles) as SCHED_BG jobs
about the time-slicing:
- the SCHED_BG process is run when no interactive process is
runnable
- it starts with a 1 second slice, followed by 2, 4, 8, 16,
and longer timeslices (in order to reduce swapping).
- these slices are only interrupted by:
- an interactive process wanting the CPU
- blocking on a resource
- another SCHED_BG process is woken up
- after the timeslice is over, the process is put to sleep
for a duration of: last_timeslice * nr_background_processes
- when no background process is running/runnable, the next
SCHED_BG process to be woken up is made runnable
- the SCHED_BG processes can run together/in parrallel when
available memory is above a certain threshold (then they
can receive 'normal' timeslices)
And when free memory stays below free_pages_low for more
than 5 seconds, we can choose to have even normal processes
queued for some time (in order to reduce paging)
Where Do You Want Us To Take You Today ? (tm)
Rik.
-- Send Linux memory-management wishes to me: I'm currently looking for something to hack...