On 24/02/15 10:21, Vincent Guittot wrote: > On 19 February 2015 at 18:18, Morten Rasmussen <[email protected]> > wrote: >> On Thu, Feb 19, 2015 at 04:52:41PM +0000, Peter Zijlstra wrote: >>> On Thu, Jan 15, 2015 at 11:09:25AM +0100, Vincent Guittot wrote:
[...] >> Agreed. I think it is reasonable to assume that the arch code >> implementing arch_scale_freq_capacity() does it's best to make it fast >> for the particular architecture. Since the scaling factor to be returned >> by the function may be obtained in different ways for different >> architectures the caching should be done on the arch side. >> >>> But lets see, I've yet to see an actual implementation of it; and its >>> got that sd argument, curious what you're going to do with that. >> >> So we do have an RFC implementation for ARM already which I posted in >> December and is also included in the rather large RFC posting I did some >> weeks ago. That one basically reads two atomic variables and returns the >> ratio between the two. I have yet to benchmark how horribly expensive it >> is though. The sd argument is ignored. We might actually not need it at >> all? > > For consistency across all arch_scale_xx_capacity, i would prefer to > keep the same prototype interface (struct sched_domain *sd, int cpu) > even if it's not used ofr now Agreed. Once we call arch_scale_xx_capacity [xx = freq, cpu] in the PELT code (i.e. w/ sd = NULL) we have to make sure that default_scale_cpu_capacity() can be called w/ sd = NULL too for platforms which are not providing their own arch_scale_cpu_capacity() function. It's already part of '[RFCv3 PATCH 00/48] sched: Energy cost model for energy-aware scheduling' https://lkml.org/lkml/2015/2/4/573 [...] -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
