RE: unnecessary timer interrupt of slab.c and bdi tasks when thesystem is in sleep state

[Van De Ven, Arjan]

> > > I found some unnecessary timer interrupts when the system enter
> sleep state.
> > > (1)     /mm/slab.c
> > > cache_reap() clean up on allocated memory every 2s. If the system
> is in sleep state, the system is waked-up when this timer expires. In
> fact,
> > > there isn't more slabs to been cleaned up in sleep state.
> >
> > Right. We could switch off the timer when idle without much of an
> issue.
> > The expiration of the caches wont occur and so we will have stale
> objects
> > on the queues when we exit sleep state. You could flush the queues
> before
> > switching off the timers?
> 
> 
> May be flushing the queue everytime we enter nohz is too much, as that
> can
> happen very often?
> 


the slab timer is already deferable... which means it won't hit while the system is completely idle.
I think this part of the original report is a red herring found on an older kernel.

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