linux-kernel - [PATCH v1 1/3] perf/core: store context switch out type into Perf trace

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <5fef4482-a358-dd9b-44ea-6e0afa4106be@linux.intel.com>
Date:   Mon, 5 Mar 2018 14:36:46 +0300
From:   Alexey Budankov <alexey.budankov@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Dmitri Prokhorov <Dmitry.Prohorov@...el.com>
Subject: [PATCH v1 1/3] perf/core: store context switch out type into Perf
 trace


Store thread context-switch-out event type into Perf trace as a part of 
PERF_RECORD_SWITCH[_CPU_WIDE] records.

Introduced types of switch-out events assumed to be 
a) preempt: task->state == TASK_RUNNING and b) yield: !preempt;

New yield event type is encoded using special 
PERF_RECORD_MISC_SWITCH_OUT_YIELD bit extending PERF_RECORD_MISC_SWITCH_OUT 
meaning traditional preemption switch out event:

    misc &= PERF_RECORD_MISC_SWITCH_OUT | PERF_RECORD_MISC_SWITCH_OUT_YIELD
	
Signed-off-by: Alexey Budankov <alexey.budankov@...ux.intel.com>
---
 include/uapi/linux/perf_event.h | 5 +++++
 kernel/events/core.c            | 4 +++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 6f873503552d..0339c829cda5 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -654,6 +654,11 @@ struct perf_event_mmap_page {
  * perf_event_attr::precise_ip.
  */
 #define PERF_RECORD_MISC_EXACT_IP		(1 << 14)
+/*
+ * Indicates that thread explicitly yielded cpu due to
+ * a call of some synchronization API e.g. futex system call
+ */
+#define PERF_RECORD_MISC_SWITCH_OUT_YIELD	(1 << 14)
 /*
  * Reserve the last bit to indicate some extended misc field
  */
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 57898102847f..1faa6dde090c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7216,6 +7216,8 @@ static void perf_event_switch(struct task_struct *task,
 			      struct task_struct *next_prev, bool sched_in)
 {
 	struct perf_switch_event switch_event;
+	__u16 switch_type = sched_in ? 0 : PERF_RECORD_MISC_SWITCH_OUT |
+		(task->state == TASK_RUNNING ? 0 : PERF_RECORD_MISC_SWITCH_OUT_YIELD);
 
 	/* N.B. caller checks nr_switch_events != 0 */
 
@@ -7225,7 +7227,7 @@ static void perf_event_switch(struct task_struct *task,
 		.event_id	= {
 			.header = {
 				/* .type */
-				.misc = sched_in ? 0 : PERF_RECORD_MISC_SWITCH_OUT,
+				.misc = switch_type,
 				/* .size */
 			},
 			/* .next_prev_pid */