On Wed, Sep 12, 2018 at 06:35:15PM +0100, Patrick Bellasi wrote: > On 12-Sep 18:12, Peter Zijlstra wrote:
> > No idea; but if you want to go all fancy you can replace he whole > > uclamp_map thing with something like: > > > > struct uclamp_map { > > union { > > struct { > > unsigned long v : 10; > > unsigned long c : BITS_PER_LONG - 10; > > }; > > atomic_long_t s; > > }; > > }; > > That sounds really cool and scary at the same time :) > > The v:10 requires that we never set SCHED_CAPACITY_SCALE>1024 > or that we use it to track a percentage value (i.e. [0..100]). Or we pick 11 bits, it seems unlikely that capacity be larger than 2k. > One of the last patches introduces percentage values to userspace. > But, I was considering that in kernel space we should always track > full scale utilization values. > > The c:(BITS_PER_LONG-10) restricts the range of concurrently active > SE refcounting the same clamp value. Which, for some 32bit systems is > only 4 milions among tasks and cgroups... maybe still reasonable... Yeah, on 32bit having 4M tasks seems 'unlikely'.