From 68bc30bb9f33fc8d11e3d110d29e06490896a999 Mon Sep 17 00:00:00 2001 From: Aubrey Li Date: Thu, 6 Jun 2019 09:22:34 +0800 Subject: proc: Add /proc//arch_status Exposing architecture specific per process information is useful for various reasons. An example is the AVX512 usage on x86 which is important for task placement for power/performance optimizations. Adding this information to the existing /prcc/pid/status file would be the obvious choise, but it has been agreed on that a explicit arch_status file is better in separating the generic and architecture specific information. [ tglx: Massage changelog ] Signed-off-by: Aubrey Li Signed-off-by: Thomas Gleixner Acked-by: Andrew Morton 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: Linux API Link: https://lkml.kernel.org/r/20190606012236.9391-1-aubrey.li@linux.intel.com --- fs/proc/Kconfig | 4 ++++ fs/proc/base.c | 6 ++++++ include/linux/proc_fs.h | 9 +++++++++ 3 files changed, 19 insertions(+) diff --git a/fs/proc/Kconfig b/fs/proc/Kconfig index 62ee41b4bbd0..4c3dcb718961 100644 --- a/fs/proc/Kconfig +++ b/fs/proc/Kconfig @@ -98,3 +98,7 @@ config PROC_CHILDREN Say Y if you are running any user-space software which takes benefit from this interface. For example, rkt is such a piece of software. + +config PROC_PID_ARCH_STATUS + def_bool n + depends on PROC_FS diff --git a/fs/proc/base.c b/fs/proc/base.c index 9c8ca6cd3ce4..ec436c61eece 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -3061,6 +3061,9 @@ static const struct pid_entry tgid_base_stuff[] = { #ifdef CONFIG_STACKLEAK_METRICS ONE("stack_depth", S_IRUGO, proc_stack_depth), #endif +#ifdef CONFIG_PROC_PID_ARCH_STATUS + ONE("arch_status", S_IRUGO, proc_pid_arch_status), +#endif }; static int proc_tgid_base_readdir(struct file *file, struct dir_context *ctx) @@ -3449,6 +3452,9 @@ static const struct pid_entry tid_base_stuff[] = { #ifdef CONFIG_LIVEPATCH ONE("patch_state", S_IRUSR, proc_pid_patch_state), #endif +#ifdef CONFIG_PROC_PID_ARCH_STATUS + ONE("arch_status", S_IRUGO, proc_pid_arch_status), +#endif }; static int proc_tid_base_readdir(struct file *file, struct dir_context *ctx) diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h index 52a283ba0465..a705aa2d03f9 100644 --- a/include/linux/proc_fs.h +++ b/include/linux/proc_fs.h @@ -75,6 +75,15 @@ struct proc_dir_entry *proc_create_net_single_write(const char *name, umode_t mo void *data); extern struct pid *tgid_pidfd_to_pid(const struct file *file); +#ifdef CONFIG_PROC_PID_ARCH_STATUS +/* + * The architecture which selects CONFIG_PROC_PID_ARCH_STATUS must + * provide proc_pid_arch_status() definition. + */ +int proc_pid_arch_status(struct seq_file *m, struct pid_namespace *ns, + struct pid *pid, struct task_struct *task); +#endif /* CONFIG_PROC_PID_ARCH_STATUS */ + #else /* CONFIG_PROC_FS */ static inline void proc_root_init(void) -- cgit v1.2.3 From 0c608dad2a771c0a11b6d12148d1a8b975e015d4 Mon Sep 17 00:00:00 2001 From: Aubrey Li Date: Thu, 6 Jun 2019 09:22:35 +0800 Subject: 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 */ -- cgit v1.2.3 From 711486fd18596315d42cebaac3dba8c408f60a3d Mon Sep 17 00:00:00 2001 From: Aubrey Li Date: Thu, 6 Jun 2019 09:22:36 +0800 Subject: Documentation/filesystems/proc.txt: Add arch_status file Add documentation for /proc//arch_status file and the x86 specific AVX512_elapsed_ms entry in it. [ tglx: Massage 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/20190606012236.9391-3-aubrey.li@linux.intel.com --- Documentation/filesystems/proc.txt | 40 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 66cad5c86171..a226061fa109 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -45,6 +45,7 @@ Table of Contents 3.9 /proc//map_files - Information about memory mapped files 3.10 /proc//timerslack_ns - Task timerslack value 3.11 /proc//patch_state - Livepatch patch operation state + 3.12 /proc//arch_status - Task architecture specific information 4 Configuring procfs 4.1 Mount options @@ -1948,6 +1949,45 @@ patched. If the patch is being enabled, then the task has already been patched. If the patch is being disabled, then the task hasn't been unpatched yet. +3.12 /proc//arch_status - task architecture specific status +------------------------------------------------------------------- +When CONFIG_PROC_PID_ARCH_STATUS is enabled, this file displays the +architecture specific status of the task. + +Example +------- + $ cat /proc/6753/arch_status + AVX512_elapsed_ms: 8 + +Description +----------- + +x86 specific entries: +--------------------- + AVX512_elapsed_ms: + ------------------ + If AVX512 is supported on the machine, this entry shows the milliseconds + elapsed since the last time AVX512 usage was recorded. The recording + happens on a best effort basis when a task is scheduled out. This means + that the value depends on two factors: + + 1) The time which the task spent on the CPU without being scheduled + out. With CPU isolation and a single runnable task this can take + several seconds. + + 2) The time since the task was scheduled out last. Depending on the + reason for being scheduled out (time slice exhausted, syscall ...) + this can be arbitrary long time. + + As a consequence the value cannot be considered precise and authoritative + information. The application which uses this information has to be aware + of the overall scenario on the system in order to determine whether a + task is a real AVX512 user or not. Precise information can be obtained + with performance counters. + + A special value of '-1' indicates that no AVX512 usage was recorded, thus + the task is unlikely an AVX512 user, but depends on the workload and the + scheduling scenario, it also could be a false negative mentioned above. ------------------------------------------------------------------------------ Configuring procfs -- cgit v1.2.3