Ingo Molnar wrote:
* Nick Piggin <[email protected]> wrote:
I'm not very familiar with the -rt tree, but possibly what should be
happening, if interrupts are executed in process context and allowed
to schedule, is that their memory allocations should also be allowed
to reclaim memory.
indeed - very good point. Emin, could you try the patch below [which
isnt a full solution but should be a good first approximation], does it
make any difference?
OTOH, I guess for a deterministic realtime system, you need to
allocate fixed minimum amounts of memory for each element of the
system so you never run out like this.
yeah, preallocation is pretty much the only way to go for deterministic
workloads. Still, networking (and other complex subsystems) can still be
used in parallel to deterministic tasks - and those should not be
starved easier when PREEMPT_RT is enabled. In fact, with the patch below
it could become much more robust - we could in fact achieve to never
fail an allocation due to being in an atomic context.
Yes, that patch is basically what I had in mind.
Is -rt ever allocating memory from really-hard-don't-preempt-me context?
I guess not, unless the zone->lock is one of those locks too, right?
Should you add a
#else
BUG_ON(_really_dont_preempt_me());
#endif
just for safety, or will such misusage get caught elsewhere (eg. when
attempting to take zone->lock).
Thanks,
Nick
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