Re: [PATCH] optional non-interactive mode for cpu scheduler

[Con Kolivas]

Ingo Molnar wrote:
> SCHED_ISO would be interesting, 

Cool! I've been toying with this too :)

> but all SCHED_BATCH patches that i've
> seen so far were fundamentally broken. [ none protects against the
> possibility of a simple CPU hog starving a SCHED_BATCH task in kernel
> mode holding say /home's i_sem forever. None except the one i wrote a
> couple of years ago that is ;-) ]

I guess the one I wrote for staircase is inadequate too. Although in the 
field the implementation has been safe as far as I can tell.

I'm thinking of holding off for a bit to allow those current changes to 
be tried in -mm for a bit.

I have two more questions - there are already userspace tools and older 
out-of-tree kernels (inluding my current one) that use SCHED_BATCH and 
SCHED_ISO.

Should we respect the values for these policies and use numbering 
consistent with them (meaning SCHED_BATCH at 3 would be reserved but not 
used) or should we dish out values according to when they're implemented 
and demand userspace be updated.

Should we move to a policy bitmask numbering system and/or make 
SCHED_CPUBOUND, SCHED_ISO etc subpolicies of SCHED_NORMAL?

Regards,
Con

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