On Fri, Mar 23, 2018 at 9:57 AM, Rafael J. Wysocki <raf...@kernel.org> wrote: > On Fri, Mar 23, 2018 at 4:19 AM, Doug Smythies <dsmyth...@telus.net> wrote: >> On 2018.03.22 12:12 Doug Smythies wrote: >>>On 2018.03.22 09:32 Rik van Riel wrote: >>>> On Wed, 2018-03-14 at 13:04 +0100, Peter Zijlstra wrote: >>>> >>>>> On x86 we don't have to use that time_check_counter thing, >>>>> sched_clock() >>>>> is really cheap, not sure if it makes sense on other platforms. >>>> >>>> Are you sure? I saw a 5-10% increase in CPU use, >>>> for a constant query rate to a memcache style >>>> workload, with v3 of this patch. >>> >>> I would very much like to be able to repeat your test results. >>> However, I am not sure what you mean by "memcache style workload". >>> Is there a test you can point me to? Say a Phoronix type test, for example. >>> >>> All of my tests with the V3 of this patch have been fine. >> >> What is the difference between sched_clock() talked about herein, >> and local_clock() used in the patch? > > It is almost the same (modulo offset) unless sched_clock_stable() > returns 'false'. > >> I'm not sure how good it is but I made a test. I didn't believe >> the results, so I did it 3 times. >> >> V7.3 is as from the git branch. >> V7.3p is plus the patch adding the counter loop to poll_state.c >> >> The test is a tight loop (about 19600 loops per second) running >> on all 8 CPUs. I can not seem to get my system to use Idle State >> 0, so I disabled Idle States 1 and 2 to force use of Idle State 0. >> >> V7.3 uses a processor package power of 62.5 Watts >> V7.3p uses a processor package power of 53.4 Watts, or 14.6% less power. >> >> The loop times do not change. >> The Idle state 0 residency per unit time does not change. > > OK, so this means that the results should improve for Rik with this > patch too. :-)
BTW, can you possibly check how much of a difference it makes to reduce POLL_IDLE_COUNT in the patch to, say, 500 or even more? The lower it is, the less noise it will introduce AFAICS.
