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authorLinus Torvalds <torvalds@linux-foundation.org>2019-07-08 17:28:57 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-07-08 17:28:57 -0700
commit3431a940bb6c3969240d91314d654ebac7e12b09 (patch)
tree8d75363fe5bc959bf03d72bc1c00275fb759f153
parent5b7a2095232d026d4537c4be54040c0f10525b5b (diff)
parent711486fd18596315d42cebaac3dba8c408f60a3d (diff)
download96b-common-3431a940bb6c3969240d91314d654ebac7e12b09.tar.gz
Merge branch 'x86-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 AVX512 status update from Ingo Molnar: "This adds a new ABI that the main scheduler probably doesn't want to deal with but HPC job schedulers might want to use: the AVX512_elapsed_ms field in the new /proc/<pid>/arch_status task status file, which allows the user-space job scheduler to cluster such tasks, to avoid turbo frequency drops" * 'x86-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: Documentation/filesystems/proc.txt: Add arch_status file x86/process: Add AVX-512 usage elapsed time to /proc/pid/arch_status proc: Add /proc/<pid>/arch_status
-rw-r--r--Documentation/filesystems/proc.txt40
-rw-r--r--arch/x86/Kconfig1
-rw-r--r--arch/x86/kernel/fpu/xstate.c47
-rw-r--r--fs/proc/Kconfig4
-rw-r--r--fs/proc/base.c6
-rw-r--r--include/linux/proc_fs.h9
6 files changed, 107 insertions, 0 deletions
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/<pid>/map_files - Information about memory mapped files
3.10 /proc/<pid>/timerslack_ns - Task timerslack value
3.11 /proc/<pid>/patch_state - Livepatch patch operation state
+ 3.12 /proc/<pid>/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/<pid>/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
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index fbabf59692ff..3b3acb7f1b07 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -220,6 +220,7 @@ 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 7b4c52aa929f..e5cb67d67c03 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -8,6 +8,8 @@
#include <linux/cpu.h>
#include <linux/mman.h>
#include <linux/pkeys.h>
+#include <linux/seq_file.h>
+#include <linux/proc_fs.h>
#include <asm/fpu/api.h>
#include <asm/fpu/internal.h>
@@ -1231,3 +1233,48 @@ 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 */
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 255f6754c70d..c40fca98f2b7 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)
@@ -3448,6 +3451,9 @@ 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)