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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 /src/core/cgroup.c
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.
Diffstat (limited to 'src/core/cgroup.c')
-rw-r--r--src/core/cgroup.c23
1 files changed, 22 insertions, 1 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;