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. :-) Thanks!
