Messages in this thread Patch in this message | | | Date | Fri, 15 Dec 2023 10:41:40 +0800 | Subject | Re: [PATCH] cpufreq: CPPC: Resolve the large frequency discrepancy from cpuinfo_cur_freq | From | "lihuisong (C)" <> |
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Hi Rafael,
Thanks for your review.😁
在 2023/12/15 3:31, Rafael J. Wysocki 写道: > On Tue, Dec 12, 2023 at 8:26 AM Huisong Li <lihuisong@huawei.com> wrote: >> Many developers found that the cpu current frequency is greater than >> the maximum frequency of the platform, please see [1], [2] and [3]. >> >> In the scenarios with high memory access pressure, the patch [1] has >> proved the significant latency of cpc_read() which is used to obtain >> delivered and reference performance counter cause an absurd frequency. >> The sampling interval for this counters is very critical and is expected >> to be equal. However, the different latency of cpc_read() has a direct >> impact on their sampling interval. >> >> This patch adds a interface, cpc_read_arch_counters_on_cpu, to read >> delivered and reference performance counter together. According to my >> test[4], the discrepancy of cpu current frequency in the scenarios with >> high memory access pressure is lower than 0.2% by stress-ng application. >> >> [1] https://lore.kernel.org/all/20231025093847.3740104-4-zengheng4@huawei.com/ >> [2] https://lore.kernel.org/all/20230328193846.8757-1-yang@os.amperecomputing.com/ >> [3] https://lore.kernel.org/all/20230418113459.12860-7-sumitg@nvidia.com/ >> >> [4] My local test: >> The testing platform enable SMT and include 128 logical CPU in total, >> and CPU base frequency is 2.7GHz. Reading "cpuinfo_cur_freq" for each >> physical core on platform during the high memory access pressure from >> stress-ng, and the output is as follows: >> 0: 2699133 2: 2699942 4: 2698189 6: 2704347 >> 8: 2704009 10: 2696277 12: 2702016 14: 2701388 >> 16: 2700358 18: 2696741 20: 2700091 22: 2700122 >> 24: 2701713 26: 2702025 28: 2699816 30: 2700121 >> 32: 2700000 34: 2699788 36: 2698884 38: 2699109 >> 40: 2704494 42: 2698350 44: 2699997 46: 2701023 >> 48: 2703448 50: 2699501 52: 2700000 54: 2699999 >> 56: 2702645 58: 2696923 60: 2697718 62: 2700547 >> 64: 2700313 66: 2700000 68: 2699904 70: 2699259 >> 72: 2699511 74: 2700644 76: 2702201 78: 2700000 >> 80: 2700776 82: 2700364 84: 2702674 86: 2700255 >> 88: 2699886 90: 2700359 92: 2699662 94: 2696188 >> 96: 2705454 98: 2699260 100: 2701097 102: 2699630 >> 104: 2700463 106: 2698408 108: 2697766 110: 2701181 >> 112: 2699166 114: 2701804 116: 2701907 118: 2701973 >> 120: 2699584 122: 2700474 124: 2700768 126: 2701963 >> >> Signed-off-by: Huisong Li <lihuisong@huawei.com> > First off, please Cc ACPI-related patches to linux-acpi.
got it.
+linux-acpi@vger.kernel.org
> >> --- >> arch/arm64/kernel/topology.c | 43 ++++++++++++++++++++++++++++++++++-- >> drivers/acpi/cppc_acpi.c | 22 +++++++++++++++--- >> include/acpi/cppc_acpi.h | 5 +++++ >> 3 files changed, 65 insertions(+), 5 deletions(-) >> >> diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c >> index 7d37e458e2f5..c3122154d738 100644 >> --- a/arch/arm64/kernel/topology.c >> +++ b/arch/arm64/kernel/topology.c >> @@ -299,6 +299,11 @@ core_initcall(init_amu_fie); >> #ifdef CONFIG_ACPI_CPPC_LIB >> #include <acpi/cppc_acpi.h> >> >> +struct amu_counters { >> + u64 corecnt; >> + u64 constcnt; >> +}; >> + >> static void cpu_read_corecnt(void *val) >> { >> /* >> @@ -322,8 +327,27 @@ static void cpu_read_constcnt(void *val) >> 0UL : read_constcnt(); >> } >> >> +static void cpu_read_amu_counters(void *data) >> +{ >> + struct amu_counters *cnt = (struct amu_counters *)data; >> + >> + /* >> + * The running time of the this_cpu_has_cap() might have a couple of >> + * microseconds and is significantly increased to tens of microseconds. >> + * But AMU core and constant counter need to be read togeter without any >> + * time interval to reduce the calculation discrepancy using this counters. >> + */ >> + if (this_cpu_has_cap(ARM64_WORKAROUND_2457168)) { >> + cnt->corecnt = read_corecnt(); > This statement is present in both branches, so can it be moved before the if ()? Yes. Do you mean adding a blank line before if()? > >> + cnt->constcnt = 0; >> + } else { >> + cnt->corecnt = read_corecnt(); >> + cnt->constcnt = read_constcnt(); >> + } >> +} >> + >> static inline >> -int counters_read_on_cpu(int cpu, smp_call_func_t func, u64 *val) >> +int counters_read_on_cpu(int cpu, smp_call_func_t func, void *data) >> { >> /* >> * Abort call on counterless CPU or when interrupts are >> @@ -335,7 +359,7 @@ int counters_read_on_cpu(int cpu, smp_call_func_t func, u64 *val) >> if (WARN_ON_ONCE(irqs_disabled())) >> return -EPERM; >> >> - smp_call_function_single(cpu, func, val, 1); >> + smp_call_function_single(cpu, func, data, 1); >> >> return 0; >> } >> @@ -364,6 +388,21 @@ bool cpc_ffh_supported(void) >> return true; >> } >> >> +int cpc_read_arch_counters_on_cpu(int cpu, u64 *delivered, u64 *reference) >> +{ >> + struct amu_counters cnts = {0}; >> + int ret; >> + >> + ret = counters_read_on_cpu(cpu, cpu_read_amu_counters, &cnts); >> + if (ret) >> + return ret; >> + >> + *delivered = cnts.corecnt; >> + *reference = cnts.constcnt; >> + >> + return 0; >> +} >> + >> int cpc_read_ffh(int cpu, struct cpc_reg *reg, u64 *val) >> { >> int ret = -EOPNOTSUPP; >> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c >> index 7ff269a78c20..f303fabd7cfe 100644 >> --- a/drivers/acpi/cppc_acpi.c >> +++ b/drivers/acpi/cppc_acpi.c >> @@ -1299,6 +1299,11 @@ bool cppc_perf_ctrs_in_pcc(void) >> } >> EXPORT_SYMBOL_GPL(cppc_perf_ctrs_in_pcc); >> >> +int __weak cpc_read_arch_counters_on_cpu(int cpu, u64 *delivered, u64 *reference) >> +{ >> + return 0; >> +} >> + >> /** >> * cppc_get_perf_ctrs - Read a CPU's performance feedback counters. >> * @cpunum: CPU from which to read counters. >> @@ -1313,7 +1318,8 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs) >> *ref_perf_reg, *ctr_wrap_reg; >> int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpunum); >> struct cppc_pcc_data *pcc_ss_data = NULL; >> - u64 delivered, reference, ref_perf, ctr_wrap_time; >> + u64 delivered = 0, reference = 0; >> + u64 ref_perf, ctr_wrap_time; >> int ret = 0, regs_in_pcc = 0; >> >> if (!cpc_desc) { >> @@ -1350,8 +1356,18 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs) >> } >> } >> >> - cpc_read(cpunum, delivered_reg, &delivered); >> - cpc_read(cpunum, reference_reg, &reference); >> + if (cpc_ffh_supported()) { >> + ret = cpc_read_arch_counters_on_cpu(cpunum, &delivered, &reference); >> + if (ret) { >> + pr_debug("read arch counters failed, ret=%d.\n", ret); >> + ret = 0; >> + } >> + } > The above is surely not applicable to every platform using CPPC. Also
cpc_ffh_supported is aimed to control only the platform supported FFH to enter. cpc_read_arch_counters_on_cpu is also needed to implemented by each platform according to their require. Here just implement this interface for arm64.
> it looks like in the ARM64_WORKAROUND_2457168 enabled case it is just > pointless overhead, because "reference" is always going to be 0 here > then. Right, it is always going to be 0 here for the ARM64_WORKAROUND_2457168 enabled case . But ARM64_WORKAROUND_2457168 is a macro releated to ARM. It seems that it is not appropriate for this macro to appear this common place for all platform, right?
> > Please clean that up. > >> + if (!delivered || !reference) { >> + cpc_read(cpunum, delivered_reg, &delivered); >> + cpc_read(cpunum, reference_reg, &reference); >> + } >> + >> cpc_read(cpunum, ref_perf_reg, &ref_perf); >> >> /* >> diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h >> index 6126c977ece0..07d4fd82d499 100644 >> --- a/include/acpi/cppc_acpi.h >> +++ b/include/acpi/cppc_acpi.h >> @@ -152,6 +152,7 @@ extern bool cpc_ffh_supported(void); >> extern bool cpc_supported_by_cpu(void); >> extern int cpc_read_ffh(int cpunum, struct cpc_reg *reg, u64 *val); >> extern int cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val); >> +extern int cpc_read_arch_counters_on_cpu(int cpu, u64 *delivered, u64 *reference); >> extern int cppc_get_epp_perf(int cpunum, u64 *epp_perf); >> extern int cppc_set_epp_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls, bool enable); >> extern int cppc_get_auto_sel_caps(int cpunum, struct cppc_perf_caps *perf_caps); >> @@ -209,6 +210,10 @@ static inline int cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val) >> { >> return -ENOTSUPP; >> } >> +static inline int cpc_read_arch_counters_on_cpu(int cpu, u64 *delivered, u64 *reference) >> +{ >> + return -EOPNOTSUPP; >> +} >> static inline int cppc_set_epp_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls, bool enable) >> { >> return -ENOTSUPP; >> -- > .
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