From 0c608dad2a771c0a11b6d12148d1a8b975e015d4 Mon Sep 17 00:00:00 2001 From: Aubrey Li Date: Thu, 6 Jun 2019 09:22:35 +0800 Subject: [PATCH] x86/process: Add AVX-512 usage elapsed time to /proc/pid/arch_status AVX-512 components usage can result in turbo frequency drop. So it's useful to expose AVX-512 usage elapsed time as a heuristic hint for user space job schedulers to cluster the AVX-512 using tasks together. Examples: $ while [ 1 ]; do cat /proc/tid/arch_status | grep AVX512; sleep 1; done AVX512_elapsed_ms: 4 AVX512_elapsed_ms: 8 AVX512_elapsed_ms: 4 This means that 4 milliseconds have elapsed since the tsks AVX512 usage was detected when the task was scheduled out. $ cat /proc/tid/arch_status | grep AVX512 AVX512_elapsed_ms: -1 '-1' indicates that no AVX512 usage was recorded for this task. The time exposed is not necessarily accurate when the arch_status file is read as the AVX512 usage is only evaluated when a task is scheduled out. Accurate usage information can be obtained with performance counters. [ tglx: Massaged changelog ] Signed-off-by: Aubrey Li Signed-off-by: Thomas Gleixner Cc: akpm@linux-foundation.org Cc: peterz@infradead.org Cc: hpa@zytor.com Cc: ak@linux.intel.com Cc: tim.c.chen@linux.intel.com Cc: dave.hansen@intel.com Cc: arjan@linux.intel.com Cc: adobriyan@gmail.com Cc: aubrey.li@intel.com Cc: linux-api@vger.kernel.org Cc: Andy Lutomirski Cc: Peter Zijlstra Cc: Andi Kleen Cc: Tim Chen Cc: Dave Hansen Cc: Arjan van de Ven Cc: Alexey Dobriyan Cc: Andrew Morton Cc: Linux API Link: https://lkml.kernel.org/r/20190606012236.9391-2-aubrey.li@linux.intel.com --- arch/x86/Kconfig | 1 + arch/x86/kernel/fpu/xstate.c | 47 ++++++++++++++++++++++++++++++++++++ 2 files changed, 48 insertions(+) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 2bbbd4d1ba31..8a49b4b03f6b 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -217,6 +217,7 @@ config X86 select USER_STACKTRACE_SUPPORT select VIRT_TO_BUS select X86_FEATURE_NAMES if PROC_FS + select PROC_PID_ARCH_STATUS if PROC_FS config INSTRUCTION_DECODER def_bool y diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index 3c36dd1784db..591ddde3b3e8 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -8,6 +8,8 @@ #include #include #include +#include +#include #include #include @@ -1240,3 +1242,48 @@ int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf) return 0; } + +#ifdef CONFIG_PROC_PID_ARCH_STATUS +/* + * Report the amount of time elapsed in millisecond since last AVX512 + * use in the task. + */ +static void avx512_status(struct seq_file *m, struct task_struct *task) +{ + unsigned long timestamp = READ_ONCE(task->thread.fpu.avx512_timestamp); + long delta; + + if (!timestamp) { + /* + * Report -1 if no AVX512 usage + */ + delta = -1; + } else { + delta = (long)(jiffies - timestamp); + /* + * Cap to LONG_MAX if time difference > LONG_MAX + */ + if (delta < 0) + delta = LONG_MAX; + delta = jiffies_to_msecs(delta); + } + + seq_put_decimal_ll(m, "AVX512_elapsed_ms:\t", delta); + seq_putc(m, '\n'); +} + +/* + * Report architecture specific information + */ +int proc_pid_arch_status(struct seq_file *m, struct pid_namespace *ns, + struct pid *pid, struct task_struct *task) +{ + /* + * Report AVX512 state if the processor and build option supported. + */ + if (cpu_feature_enabled(X86_FEATURE_AVX512F)) + avx512_status(m, task); + + return 0; +} +#endif /* CONFIG_PROC_PID_ARCH_STATUS */