On Thu, 9 Apr 2015, Peter Zijlstra wrote:
On Thu, Apr 09, 2015 at 11:18:52AM +0200, Thomas Gleixner wrote:
On Thu, 9 Apr 2015, Peter Zijlstra wrote:
On Thu, Apr 09, 2015 at 09:20:39AM +0200, Ingo Molnar wrote:
if at least one base is active (on my fairly standard system all cpus have at least one active hrtimer base all the time - and many cpus have two bases active), then we run hrtimer_get_softirq_time(), which dirties the cachelines of all 4 clock bases:
base->clock_base[HRTIMER_BASE_REALTIME].softirq_time = xtim; base->clock_base[HRTIMER_BASE_MONOTONIC].softirq_time = mono; base->clock_base[HRTIMER_BASE_BOOTTIME].softirq_time = boot; base->clock_base[HRTIMER_BASE_TAI].softirq_time = tai;so in practice we not only touch every cacheline in every timer interrupt, but we _dirty_ them, even the inactive ones.
Urgh we should really _really_ kill that entire softirq mess.
That's the !highres part. We cannot kill that one unless we remove all support for machines which do not provide hardware for highres support.
Oops, sorry I mixed up the two. Doesn't take away from the fact that I'd like to get rid of the highres softirq fallback path.
Indeed.