From cc9e303c91f5c25c49a4312552841f4c23fa2b69 Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov Date: Wed, 15 May 2019 09:59:00 +0300 Subject: x86/cpu: Disable frequency requests via aperfmperf IPI for nohz_full CPUs Since commit 7d5905dc14a8 ("x86 / CPU: Always show current CPU frequency in /proc/cpuinfo") open and read of /proc/cpuinfo sends IPI to all CPUs. Many applications read /proc/cpuinfo at the start for trivial reasons like counting cores or detecting cpu features. While sensitive workloads like DPDK network polling don't like any interrupts. Integrates this feature with cpu isolation and do not send IPIs to CPUs without housekeeping flag HK_FLAG_MISC (set by nohz_full). Code that requests cpu frequency like show_cpuinfo() falls back to the last frequency set by the cpufreq driver if this method returns 0. Signed-off-by: Konstantin Khlebnikov Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Len Brown Cc: Frederic Weisbecker Cc: "Rafael J. Wysocki" Cc: "Paul E. McKenney" Link: https://lkml.kernel.org/r/155790354043.1104.15333317408370209.stgit@buzz --- arch/x86/kernel/cpu/aperfmperf.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/cpu/aperfmperf.c b/arch/x86/kernel/cpu/aperfmperf.c index e71a6ff8a67e..e2f319dc992d 100644 --- a/arch/x86/kernel/cpu/aperfmperf.c +++ b/arch/x86/kernel/cpu/aperfmperf.c @@ -13,6 +13,7 @@ #include #include #include +#include #include "cpu.h" @@ -85,6 +86,9 @@ unsigned int aperfmperf_get_khz(int cpu) if (!boot_cpu_has(X86_FEATURE_APERFMPERF)) return 0; + if (!housekeeping_cpu(cpu, HK_FLAG_MISC)) + return 0; + aperfmperf_snapshot_cpu(cpu, ktime_get(), true); return per_cpu(samples.khz, cpu); } @@ -101,9 +105,12 @@ void arch_freq_prepare_all(void) if (!boot_cpu_has(X86_FEATURE_APERFMPERF)) return; - for_each_online_cpu(cpu) + for_each_online_cpu(cpu) { + if (!housekeeping_cpu(cpu, HK_FLAG_MISC)) + continue; if (!aperfmperf_snapshot_cpu(cpu, now, false)) wait = true; + } if (wait) msleep(APERFMPERF_REFRESH_DELAY_MS); @@ -117,6 +124,9 @@ unsigned int arch_freq_get_on_cpu(int cpu) if (!boot_cpu_has(X86_FEATURE_APERFMPERF)) return 0; + if (!housekeeping_cpu(cpu, HK_FLAG_MISC)) + return 0; + if (aperfmperf_snapshot_cpu(cpu, ktime_get(), true)) return per_cpu(samples.khz, cpu); -- cgit v1.2.3