From: Aubrey Li <aubrey.li@intel.com>
To: tglx@linutronix.de, mingo@redhat.com, peterz@infradead.org,
hpa@zytor.com
Cc: ak@linux.intel.com, tim.c.chen@linux.intel.com,
dave.hansen@intel.com, arjan@linux.intel.com,
aubrey.li@intel.com, linux-kernel@vger.kernel.org,
Aubrey Li <aubrey.li@linux.intel.com>
Subject: [PATCH v5 2/3] proc: add AVX-512 usage elapsed time to /proc/pid/status
Date: Mon, 17 Dec 2018 02:50:20 +0800 [thread overview]
Message-ID: <20181216185021.16912-2-aubrey.li@intel.com> (raw)
In-Reply-To: <20181216185021.16912-1-aubrey.li@intel.com>
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.
Example:
$ cat /proc/pid/status | grep AVX512_elapsed_ms
AVX512_elapsed_ms: 1020
The number '1020' denotes 1020 millisecond elapsed since last time
context switch the off-CPU task using AVX-512 components, thus the
task could cause core frequency drop.
Or:
$ cat /proc/pid/status | grep AVX512_elapsed_ms
AVX512_elapsed_ms: -1
The number '-1' indicates the task didn't use AVX-512 components
before thus 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.
Signed-off-by: Aubrey Li <aubrey.li@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
---
arch/x86/kernel/fpu/xstate.c | 34 ++++++++++++++++++++++++++++++++++
fs/proc/array.c | 5 +++++
2 files changed, 39 insertions(+)
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 87a57b7642d3..d084b1dc80a6 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -7,6 +7,7 @@
#include <linux/cpu.h>
#include <linux/mman.h>
#include <linux/pkeys.h>
+#include <linux/seq_file.h>
#include <asm/fpu/api.h>
#include <asm/fpu/internal.h>
@@ -1245,3 +1246,36 @@ int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf)
return 0;
}
+
+/*
+ * Report the amount of time elapsed in millisecond since last AVX512
+ * use in the task.
+ */
+void avx512_state(struct seq_file *m, struct task_struct *task)
+{
+ u64 timestamp = task->thread.fpu.avx512_timestamp;
+ s64 delta;
+
+ if (!timestamp)
+ delta = -1;
+ else {
+ WARN_ON_ONCE(jiffies_64 < timestamp);
+ delta = div_u64(jiffies64_to_nsecs(jiffies_64 - timestamp),
+ NSEC_PER_MSEC);
+ }
+
+ seq_put_decimal_ll(m, "AVX512_elapsed_ms:\t", delta);
+ seq_putc(m, '\n');
+}
+
+/*
+ * Report CPU specific thread state
+ */
+void arch_task_state(struct seq_file *m, struct task_struct *task)
+{
+ /*
+ * Report AVX512 state if the processor and build option supported.
+ */
+ if (cpu_feature_enabled(X86_FEATURE_AVX512F))
+ avx512_state(m, task);
+}
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 0ceb3b6b37e7..dd88c2219f08 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -392,6 +392,10 @@ static inline void task_core_dumping(struct seq_file *m, struct mm_struct *mm)
seq_putc(m, '\n');
}
+void __weak arch_task_state(struct seq_file *m, struct task_struct *task)
+{
+}
+
int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *task)
{
@@ -414,6 +418,7 @@ int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
task_cpus_allowed(m, task);
cpuset_task_status_allowed(m, task);
task_context_switch_counts(m, task);
+ arch_task_state(m, task);
return 0;
}
--
2.17.1
next prev parent reply other threads:[~2018-12-17 2:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-16 18:50 [PATCH v5 1/3] x86/fpu: track AVX-512 usage of tasks Aubrey Li
2018-12-16 18:50 ` Aubrey Li [this message]
2018-12-16 18:50 ` [PATCH v5 3/3] Documentation/filesystems/proc.txt: add AVX512_elapsed_ms Aubrey Li
2018-12-17 18:42 ` Tim Chen
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