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authorKyle Walker <walker.kyle.t@gmail.com>2016-06-30 15:12:18 -0400
committerKyle Walker <walker.kyle.t@gmail.com>2016-06-30 15:16:47 -0400
commit36f20ae3b2975e44b6ef17e453ae06a289e9a122 (patch)
tree9fa9abeb4e1724e4c505f193e3b69cda57b732a4 /src/core
parent7486322b99da5b4d2d00d35b310b035f936f7964 (diff)
manager: Only invoke a single sigchld per unit within a cleanup cycle
By default, each iteration of manager_dispatch_sigchld() results in a unit level sigchld event being invoked. For scope units, this results in a scope_sigchld_event() which can seemingly stall for workloads that have a large number of PIDs within the scope. The stall exhibits itself as a SIG_0 being initiated for each u->pids entry as a result of pid_is_unwaited(). v2: This patch resolves this condition by only paying to cost of a sigchld in the underlying scope unit once per sigchld iteration. A new "sigchldgen" member resides within the Unit struct. The Manager is incremented via the sd event loop, accessed via sd_event_get_iteration, and the Unit member is set to the same value as the manager each time that a sigchld event is invoked. If the Manager iteration value and Unit member match, the sigchld event is not invoked for that iteration.
Diffstat (limited to 'src/core')
-rw-r--r--src/core/manager.c13
-rw-r--r--src/core/unit.c1
-rw-r--r--src/core/unit.h3
3 files changed, 15 insertions, 2 deletions
diff --git a/src/core/manager.c b/src/core/manager.c
index 012aa6cd53..1323df7d88 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -1716,16 +1716,25 @@ static int manager_dispatch_notify_fd(sd_event_source *source, int fd, uint32_t
}
static void invoke_sigchld_event(Manager *m, Unit *u, const siginfo_t *si) {
+ uint64_t iteration;
+
assert(m);
assert(u);
assert(si);
+ sd_event_get_iteration(m->event, &iteration);
+
log_unit_debug(u, "Child "PID_FMT" belongs to %s", si->si_pid, u->id);
unit_unwatch_pid(u, si->si_pid);
- if (UNIT_VTABLE(u)->sigchld_event)
- UNIT_VTABLE(u)->sigchld_event(u, si->si_pid, si->si_code, si->si_status);
+ if (UNIT_VTABLE(u)->sigchld_event) {
+ if (set_size(u->pids) <= 1 || iteration != u->sigchldgen) {
+ UNIT_VTABLE(u)->sigchld_event(u, si->si_pid, si->si_code, si->si_status);
+ u->sigchldgen = iteration;
+ } else
+ log_debug("%s already issued a sigchld this iteration %llu, skipping. Pids still being watched %d", u->id, iteration, set_size(u->pids));
+ }
}
static int manager_dispatch_sigchld(Manager *m) {
diff --git a/src/core/unit.c b/src/core/unit.c
index 0a1a5321df..8e5395361d 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -100,6 +100,7 @@ Unit *unit_new(Manager *m, size_t size) {
u->on_failure_job_mode = JOB_REPLACE;
u->cgroup_inotify_wd = -1;
u->job_timeout = USEC_INFINITY;
+ u->sigchldgen = 0;
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);
diff --git a/src/core/unit.h b/src/core/unit.h
index 08a927962d..c41011ed9d 100644
--- a/src/core/unit.h
+++ b/src/core/unit.h
@@ -162,6 +162,9 @@ struct Unit {
* process SIGCHLD for */
Set *pids;
+ /* Used in sigchld event invocation to avoid repeat events being invoked */
+ uint64_t sigchldgen;
+
/* Used during GC sweeps */
unsigned gc_marker;