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Date: Thu, 18 Feb 2016 13:09:26 -0800 From: "Doug Smythies" <dsmythies@...us.net> To: "'Rafael J. Wysocki'" <rafael@...nel.org>, "'Mel Gorman'" <mgorman@...hsingularity.net> Cc: "'Rafael Wysocki'" <rjw@...ysocki.net>, "'Ingo Molnar'" <mingo@...nel.org>, "'Peter Zijlstra'" <peterz@...radead.org>, "'Matt Fleming'" <matt@...eblueprint.co.uk>, "'Mike Galbraith'" <umgwanakikbuti@...il.com>, "'Linux-PM'" <linux-pm@...r.kernel.org>, "'LKML'" <linux-kernel@...r.kernel.org>, "'Srinivas Pandruvada'" <srinivas.pandruvada@...ux.intel.com> Subject: RE: [PATCH 1/1] intel_pstate: Increase hold-off time before busyness is scaled On 2106.02.18 Rafael J. Wysocki wrote: On Thu, Feb 18, 2016 at 12:11 PM, Mel Gorman wrote: >> >> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net> >> --- >> drivers/cpufreq/intel_pstate.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c >> index cd83d477e32d..54250084174a 100644 >> --- a/drivers/cpufreq/intel_pstate.c >> +++ b/drivers/cpufreq/intel_pstate.c >> @@ -999,7 +999,7 @@ static inline int32_t get_target_pstate_use_performance(struct cpudata *cpu) >> sample_time = pid_params.sample_rate_ms * USEC_PER_MSEC; >> duration_us = ktime_us_delta(cpu->sample.time, >> cpu->last_sample_time); >> - if (duration_us > sample_time * 3) { >> + if (duration_us > sample_time * 12) { >> sample_ratio = div_fp(int_tofp(sample_time), >> int_tofp(duration_us)); >> core_busy = mul_fp(core_busy, sample_ratio); >> -- The immediately preceding comment needs to be changed also. Note that with duration related scaling only coming in at such a high ratio it might be worth saving the divide and just setting it to 0. > I've been considering making a change like this, but I wasn't quite > sure how much greater the multiplier should be, so I've queued this > one up for 4.6. > That said please note that we're planning to make one significant > change to intel_pstate in the 4.6 cycle that's very likely to affect > your results. Rafael: I started to test Mel's change added to your 3 patch set version 10. I only have one data point so far, I selected the test I did from one of Mel's better results (although there is no reason to expect my computer to have best results for the same operating conditions): Stock kernel 4.5-rc4 just for reference: Linux s15 4.5.0-040500rc4-generic #201602141731 SMP Sun Feb 14 22:33:37 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux Command line used: iozone -s 401408 -r 32 -f bla.bla -i 0 Output is in Kbytes/sec KB reclen write rewrite 401408 32 1895293 3035291 _________________________________________________________________ Kernel 4.5-rc4 + jrw 3 patch set version 10 (nominal 3X duration holdoff) Linux s15 4.5.0-rc4-rjwv10 #167 SMP Mon Feb 15 14:23:10 PST 2016 x86_64 x86_64 x86_64 GNU/Linux Command line used: iozone -s 401408 -r 32 -f bla.bla -i 0 Output is in Kbytes/sec KB reclen write rewrite 401408 32 2010558 3086354 401408 32 1945126 3127472 401408 32 1944807 3110387 401408 32 1948620 3110002 AVE 1962278 3108554 Performance mode, for comparison: KB reclen write rewrite 401408 32 2870111 5023311 401408 32 2869642 5149213 401408 32 2792053 5100280 401408 32 2863887 5149229 _________________________________________________________________ Kernel 4.5-rc4 + jrw 3 patch set version 10 + mg 12X duration hold-off Linux s15 4.5.0-rc4-rjwv10-12 #169 SMP Thu Feb 18 08:15:33 PST 2016 x86_64 x86_64 x86_64 GNU/Linux Command line used: iozone -s 401408 -r 32 -f bla.bla -i 0 Output is in Kbytes/sec KB reclen write rewrite 401408 32 1989670 3100580 401408 32 2062291 3112463 401408 32 2107637 3233567 401408 32 2111772 3340610 AVE 2067843 3196805 Gain Verses 3X 5.4% 2.8% _________________________________________________________________ Mel: Did you observe any downside conditions? For example, here is just an example taken some trace samples from my computer: Duration kick in = 3X Core busy = 101 Current pstate = 16 Load = 2.2% Duration = 43.815 mSec Scaled busy = 48 Next Pstate = 16 (= minimum for my computer) If duration kick in = 12X then Scaled busy = 214 Next pstate = 38 (= Max turbo for my computer) Note: I do NOT have an operational example where it matters in terms of energy use or whatever. I just suggesting that we look. ... Doug
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