| Message ID | 20191113124654.18122-6-ggherdovich@suse.cz (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
| Series | Add support for frequency invariance for (some) x86 | expand |
On Wed, 2019-11-13 at 13:46 +0100, Giovanni Gherdovich wrote: > The scheduler needs the ratio freq_curr/freq_max for frequency- > invariant > accounting. On all ATOM CPUs prior to Goldmont, set freq_max to the > 1-core > turbo ratio. > > We intended to perform tests validating that this patch doesn't > regress in > terms of energy efficiency, given that this is the primary concern on > Atom > processors. Alas, we found out that turbostat doesn't support reading > RAPL > interfaces on our test machine (Airmont), and we don't have external > equipment > to measure power consumption; all we have is the performance results > of the > benchmarks we ran. > I can run some benchmarks on this. Thanks, Srinivas > Test machine: > > Platform : Dell Wyse 3040 Thin Client[1] > CPU Model : Intel Atom x5-Z8350 (aka Cherry Trail, aka Airmont) > Fam/Mod/Ste : 6:76:4 > Topology : 1 socket, 4 cores / 4 threads > Memory : 2G > Storage : onboard flash, XFS filesystem > > [1] > https://www.dell.com/en-us/work/shop/wyse-endpoints-and-software/wyse-3040-thin-client/spd/wyse-3040-thin-client > > Base frequency and available turbo levels (MHz): > > Min Operating Freq 266 |*** > Low Freq Mode 800 |******** > Base Freq 2400 |************************ > 4 Cores 2800 |**************************** > 3 Cores 2800 |**************************** > 2 Cores 3200 |******************************** > 1 Core 3200 |******************************** > > Tested kernels: > > Baseline : v5.4-rc1, intel_pstate > passive, schedutil > Comparison #1 : v5.4-rc1, intel_pstate active > , powersave > Comparison #2 : v5.4-rc1, this patch, intel_pstate > passive, schedutil > > tbench, hackbench and kernbench performed the same under all three > kernels; > dbench ran faster with intel_pstate/powersave and the git unit tests > were a > lot faster with intel_pstate/powersave and invariant schedutil wrt > the > baseline. Not that any of this is terrbily interesting anyway, one > doesn't buy > an Atom system to go fast. Power consumption regressions aren't > expected but > we lack the equipment to make that measurement. Turbostat seems to > think that > reading RAPL on this machine isn't a good idea and we're trusting > that > decision. > > comparison ratio of performance with baseline; 1.00 means neutral, > lower is better: > > I_PSTATE FREQ-INV > ---------------------------------------- > dbench 0.90 ~ > kernbench 0.98 0.97 > gitsource 0.63 0.43 > > Signed-off-by: Giovanni Gherdovich <ggherdovich@suse.cz> > --- > arch/x86/kernel/smpboot.c | 29 +++++++++++++++++++++-------- > 1 file changed, 21 insertions(+), 8 deletions(-) > > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c > index 4d192abf337d..8988177064be 100644 > --- a/arch/x86/kernel/smpboot.c > +++ b/arch/x86/kernel/smpboot.c > @@ -1821,6 +1821,24 @@ static bool turbo_disabled(void) > return (misc_en & MSR_IA32_MISC_ENABLE_TURBO_DISABLE); > } > > +static bool slv_set_cpu_max_freq(u64 *ratio, u64 *turbo_ratio) > +{ > + int err; > + > + err = rdmsrl_safe(MSR_ATOM_CORE_RATIOS, ratio); > + if (err) > + return false; > + > + err = rdmsrl_safe(MSR_ATOM_CORE_TURBO_RATIOS, turbo_ratio); > + if (err) > + return false; > + > + *ratio = (*ratio >> 16) & 0x3F; /* max P state ratio */ > + *turbo_ratio = *turbo_ratio & 0x3F; /* 1C turbo ratio */ > + > + return true; > +} > + > #include <asm/cpu_device_id.h> > #include <asm/intel-family.h> > > @@ -1984,19 +2002,14 @@ static bool core_set_cpu_max_freq(u64 *ratio, > u64 *turbo_ratio) > > static void intel_set_cpu_max_freq(void) > { > - /* > - * TODO: add support for: > - * > - * - Atom Silvermont > - * > - * which all now get by default arch_max_freq = > SCHED_CAPACITY_SCALE > - */ > - > u64 ratio = 1, turbo_ratio = 1; > > if (turbo_disabled()) > return; > > + if (slv_set_cpu_max_freq(&ratio, &turbo_ratio)) > + goto set_value; > + > if (glm_set_cpu_max_freq(&ratio, &turbo_ratio)) > goto set_value; >
On Wed, 2019-11-13 at 08:50 -0800, Srinivas Pandruvada wrote: > On Wed, 2019-11-13 at 13:46 +0100, Giovanni Gherdovich wrote: > > The scheduler needs the ratio freq_curr/freq_max for frequency- > > invariant > > accounting. On all ATOM CPUs prior to Goldmont, set freq_max to the > > 1-core > > turbo ratio. > > > > We intended to perform tests validating that this patch doesn't > > regress in > > terms of energy efficiency, given that this is the primary concern on > > Atom > > processors. Alas, we found out that turbostat doesn't support reading > > RAPL > > interfaces on our test machine (Airmont), and we don't have external > > equipment > > to measure power consumption; all we have is the performance results > > of the > > benchmarks we ran. > > > > I can run some benchmarks on this. > That'd be appreciated, thank you Srinivas. Giovanni
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 4d192abf337d..8988177064be 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1821,6 +1821,24 @@ static bool turbo_disabled(void) return (misc_en & MSR_IA32_MISC_ENABLE_TURBO_DISABLE); } +static bool slv_set_cpu_max_freq(u64 *ratio, u64 *turbo_ratio) +{ + int err; + + err = rdmsrl_safe(MSR_ATOM_CORE_RATIOS, ratio); + if (err) + return false; + + err = rdmsrl_safe(MSR_ATOM_CORE_TURBO_RATIOS, turbo_ratio); + if (err) + return false; + + *ratio = (*ratio >> 16) & 0x3F; /* max P state ratio */ + *turbo_ratio = *turbo_ratio & 0x3F; /* 1C turbo ratio */ + + return true; +} + #include <asm/cpu_device_id.h> #include <asm/intel-family.h> @@ -1984,19 +2002,14 @@ static bool core_set_cpu_max_freq(u64 *ratio, u64 *turbo_ratio) static void intel_set_cpu_max_freq(void) { - /* - * TODO: add support for: - * - * - Atom Silvermont - * - * which all now get by default arch_max_freq = SCHED_CAPACITY_SCALE - */ - u64 ratio = 1, turbo_ratio = 1; if (turbo_disabled()) return; + if (slv_set_cpu_max_freq(&ratio, &turbo_ratio)) + goto set_value; + if (glm_set_cpu_max_freq(&ratio, &turbo_ratio)) goto set_value;
The scheduler needs the ratio freq_curr/freq_max for frequency-invariant accounting. On all ATOM CPUs prior to Goldmont, set freq_max to the 1-core turbo ratio. We intended to perform tests validating that this patch doesn't regress in terms of energy efficiency, given that this is the primary concern on Atom processors. Alas, we found out that turbostat doesn't support reading RAPL interfaces on our test machine (Airmont), and we don't have external equipment to measure power consumption; all we have is the performance results of the benchmarks we ran. Test machine: Platform : Dell Wyse 3040 Thin Client[1] CPU Model : Intel Atom x5-Z8350 (aka Cherry Trail, aka Airmont) Fam/Mod/Ste : 6:76:4 Topology : 1 socket, 4 cores / 4 threads Memory : 2G Storage : onboard flash, XFS filesystem [1] https://www.dell.com/en-us/work/shop/wyse-endpoints-and-software/wyse-3040-thin-client/spd/wyse-3040-thin-client Base frequency and available turbo levels (MHz): Min Operating Freq 266 |*** Low Freq Mode 800 |******** Base Freq 2400 |************************ 4 Cores 2800 |**************************** 3 Cores 2800 |**************************** 2 Cores 3200 |******************************** 1 Core 3200 |******************************** Tested kernels: Baseline : v5.4-rc1, intel_pstate passive, schedutil Comparison #1 : v5.4-rc1, intel_pstate active , powersave Comparison #2 : v5.4-rc1, this patch, intel_pstate passive, schedutil tbench, hackbench and kernbench performed the same under all three kernels; dbench ran faster with intel_pstate/powersave and the git unit tests were a lot faster with intel_pstate/powersave and invariant schedutil wrt the baseline. Not that any of this is terrbily interesting anyway, one doesn't buy an Atom system to go fast. Power consumption regressions aren't expected but we lack the equipment to make that measurement. Turbostat seems to think that reading RAPL on this machine isn't a good idea and we're trusting that decision. comparison ratio of performance with baseline; 1.00 means neutral, lower is better: I_PSTATE FREQ-INV ---------------------------------------- dbench 0.90 ~ kernbench 0.98 0.97 gitsource 0.63 0.43 Signed-off-by: Giovanni Gherdovich <ggherdovich@suse.cz> --- arch/x86/kernel/smpboot.c | 29 +++++++++++++++++++++-------- 1 file changed, 21 insertions(+), 8 deletions(-)