The patch titled
Subject: x86,/proc/pid/arch_status: add AVX-512 usage elapsed time
has been added to the -mm tree. Its filename is
x86-proc-pid-arch_status-add-avx-512-usage-elapsed-time.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/x86-proc-pid-arch_status-add-avx-512-usage-elapsed-time.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/x86-proc-pid-arch_status-add-avx-512-usage-elapsed-time.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Aubrey Li <aubrey.li@xxxxxxxxxxxxxxx>
Subject: x86,/proc/pid/arch_status: add AVX-512 usage elapsed time
AVX-512 components use could cause core turbo frequency drop. So it's
useful to expose AVX-512 usage elapsed time as a heuristic hint for the
user space job scheduler to cluster the AVX-512 using tasks together.
Tensorflow example:
$ 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 AVX512 usage
of tensorflow task was detected when the task was scheduled out.
Or:
$ cat /proc/tid/arch_status | grep AVX512
AVX512_elapsed_ms: -1
The number '-1' indicates that no AVX512 usage recorded before
thus the task unlikely has frequency drop issue.
User space tools may want to further check by:
$ perf stat --pid <pid> -e core_power.lvl2_turbo_license -- sleep 1
Performance counter stats for process id '3558':
3,251,565,961 core_power.lvl2_turbo_license
1.004031387 seconds time elapsed
Non-zero counter value confirms that the task causes frequency drop.
Link: http://lkml.kernel.org/r/20190606012236.9391-2-aubrey.li@xxxxxxxxxxxxxxx
Signed-off-by: Aubrey Li <aubrey.li@xxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/Kconfig | 1
arch/x86/kernel/fpu/xstate.c | 47 +++++++++++++++++++++++++++++++++
2 files changed, 48 insertions(+)
--- a/arch/x86/Kconfig~x86-proc-pid-arch_status-add-avx-512-usage-elapsed-time
+++ a/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
--- a/arch/x86/kernel/fpu/xstate.c~x86-proc-pid-arch_status-add-avx-512-usage-elapsed-time
+++ a/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>
@@ -1240,3 +1242,48 @@ int copy_user_to_xstate(struct xregs_sta
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 */
_
Patches currently in -mm which might be from aubrey.li@xxxxxxxxxxxxxxx are
proc-add-proc-pid-arch_status.patch
x86-proc-pid-arch_status-add-avx-512-usage-elapsed-time.patch
documentation-filesystems-proctxt-add-arch_status-file.patch
