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authorLennart Poettering <lennart@poettering.net>2016-08-18 20:58:10 +0200
committerLennart Poettering <lennart@poettering.net>2016-08-22 16:14:21 +0200
commitfe700f46ec5490efcb8da49e644bb4d781f896f2 (patch)
tree20564975ed016c16cc4029ca0c46582e484d15a9
parent8b3b6f588cd9aecbfb17664a5961f789b5a11386 (diff)
core: cache last CPU usage counter, before destorying a cgroup
It is useful for clients to be able to read the last CPU usage counter value of a unit even if the unit is already terminated. Hence, before destroying a cgroup's cgroup cache the last CPU usage counter and return it if the cgroup is gone.
-rw-r--r--src/core/cgroup.c23
-rw-r--r--src/core/unit.c16
-rw-r--r--src/core/unit.h1
3 files changed, 37 insertions, 3 deletions
diff --git a/src/core/cgroup.c b/src/core/cgroup.c
index 086cd7a789..20f9f9fc7e 100644
--- a/src/core/cgroup.c
+++ b/src/core/cgroup.c
@@ -1524,6 +1524,8 @@ void unit_prune_cgroup(Unit *u) {
if (!u->cgroup_path)
return;
+ (void) unit_get_cpu_usage(u, NULL); /* Cache the last CPU usage value before we destroy the cgroup */
+
is_root_slice = unit_has_name(u, SPECIAL_ROOT_SLICE);
r = cg_trim_everywhere(u->manager->cgroup_supported, u->cgroup_path, !is_root_slice);
@@ -2044,7 +2046,21 @@ int unit_get_cpu_usage(Unit *u, nsec_t *ret) {
nsec_t ns;
int r;
+ assert(u);
+
+ /* Retrieve the current CPU usage counter. This will subtract the CPU counter taken when the unit was
+ * started. If the cgroup has been removed already, returns the last cached value. To cache the value, simply
+ * call this function with a NULL return value. */
+
r = unit_get_cpu_usage_raw(u, &ns);
+ if (r == -ENODATA && u->cpu_usage_last != NSEC_INFINITY) {
+ /* If we can't get the CPU usage anymore (because the cgroup was already removed, for example), use our
+ * cached value. */
+
+ if (ret)
+ *ret = u->cpu_usage_last;
+ return 0;
+ }
if (r < 0)
return r;
@@ -2053,7 +2069,10 @@ int unit_get_cpu_usage(Unit *u, nsec_t *ret) {
else
ns = 0;
- *ret = ns;
+ u->cpu_usage_last = ns;
+ if (ret)
+ *ret = ns;
+
return 0;
}
@@ -2063,6 +2082,8 @@ int unit_reset_cpu_usage(Unit *u) {
assert(u);
+ u->cpu_usage_last = NSEC_INFINITY;
+
r = unit_get_cpu_usage_raw(u, &ns);
if (r < 0) {
u->cpu_usage_base = 0;
diff --git a/src/core/unit.c b/src/core/unit.c
index 6d92eb0c30..03ee6424fa 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -102,6 +102,7 @@ Unit *unit_new(Manager *m, size_t size) {
u->job_timeout = USEC_INFINITY;
u->ref_uid = UID_INVALID;
u->ref_gid = GID_INVALID;
+ u->cpu_usage_last = NSEC_INFINITY;
RATELIMIT_INIT(u->start_limit, m->default_start_limit_interval, m->default_start_limit_burst);
RATELIMIT_INIT(u->auto_stop_ratelimit, 10 * USEC_PER_SEC, 16);
@@ -2620,7 +2621,10 @@ int unit_serialize(Unit *u, FILE *f, FDSet *fds, bool serialize_jobs) {
unit_serialize_item(u, f, "assert-result", yes_no(u->assert_result));
unit_serialize_item(u, f, "transient", yes_no(u->transient));
+
unit_serialize_item_format(u, f, "cpu-usage-base", "%" PRIu64, u->cpu_usage_base);
+ if (u->cpu_usage_last != NSEC_INFINITY)
+ unit_serialize_item_format(u, f, "cpu-usage-last", "%" PRIu64, u->cpu_usage_last);
if (u->cgroup_path)
unit_serialize_item(u, f, "cgroup", u->cgroup_path);
@@ -2843,11 +2847,19 @@ int unit_deserialize(Unit *u, FILE *f, FDSet *fds) {
continue;
- } else if (streq(l, "cpu-usage-base") || streq(l, "cpuacct-usage-base")) {
+ } else if (STR_IN_SET(l, "cpu-usage-base", "cpuacct-usage-base")) {
r = safe_atou64(v, &u->cpu_usage_base);
if (r < 0)
- log_unit_debug(u, "Failed to parse CPU usage %s, ignoring.", v);
+ log_unit_debug(u, "Failed to parse CPU usage base %s, ignoring.", v);
+
+ continue;
+
+ } else if (streq(l, "cpu-usage-last")) {
+
+ r = safe_atou64(v, &u->cpu_usage_last);
+ if (r < 0)
+ log_unit_debug(u, "Failed to read CPU usage last %s, ignoring.", v);
continue;
diff --git a/src/core/unit.h b/src/core/unit.h
index e5a2a77b7b..31f0fef87b 100644
--- a/src/core/unit.h
+++ b/src/core/unit.h
@@ -194,6 +194,7 @@ struct Unit {
/* Where the cpu.stat or cpuacct.usage was at the time the unit was started */
nsec_t cpu_usage_base;
+ nsec_t cpu_usage_last; /* the most recently read value */
/* Counterparts in the cgroup filesystem */
char *cgroup_path;