* Peter Zijlstra peterz@infradead.org wrote:
On Thu, Apr 09, 2015 at 08:28:41AM +0200, Ingo Molnar wrote:
Btw., does cpu_base->active_bases even make sense? hrtimer bases are fundamentally percpu, and to check whether there are any pending timers is a very simple check:
base->active->next != NULL
Yeah, that's 3 pointer dereferences from cpu_base, iow you traded a single bit test on an already loaded word for 3 potential cacheline misses.
But the clock bases are not aligned to cachelines, and we have 4 of them. So in practice when we access one, we'll load the next one anyway.
Furthermore the simplification is measurable, and a fair bit of it is in various fast paths. I'd rather trade a bit of a cacheline footprint for less overall complexity and faster code.
Thanks,
Ingo