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-rw-r--r--src/basic/util.c55
-rw-r--r--src/basic/util.h3
2 files changed, 58 insertions, 0 deletions
diff --git a/src/basic/util.c b/src/basic/util.c
index 09d16697b7..c4b6fc2925 100644
--- a/src/basic/util.c
+++ b/src/basic/util.c
@@ -832,6 +832,61 @@ uint64_t physical_memory_scale(uint64_t v, uint64_t max) {
return r;
}
+uint64_t system_tasks_max(void) {
+
+#if SIZEOF_PID_T == 4
+#define TASKS_MAX ((uint64_t) (INT32_MAX-1))
+#elif SIZEOF_PID_T == 2
+#define TASKS_MAX ((uint64_t) (INT16_MAX-1))
+#else
+#error "Unknown pid_t size"
+#endif
+
+ _cleanup_free_ char *value = NULL, *root = NULL;
+ uint64_t a = TASKS_MAX, b = TASKS_MAX;
+
+ /* Determine the maximum number of tasks that may run on this system. We check three sources to determine this
+ * limit:
+ *
+ * a) the maximum value for the pid_t type
+ * b) the cgroups pids_max attribute for the system
+ * c) the kernel's configure maximum PID value
+ *
+ * And then pick the smallest of the three */
+
+ if (read_one_line_file("/proc/sys/kernel/pid_max", &value) >= 0)
+ (void) safe_atou64(value, &a);
+
+ if (cg_get_root_path(&root) >= 0) {
+ value = mfree(value);
+
+ if (cg_get_attribute("pids", root, "pids.max", &value) >= 0)
+ (void) safe_atou64(value, &b);
+ }
+
+ return MIN3(TASKS_MAX,
+ a <= 0 ? TASKS_MAX : a,
+ b <= 0 ? TASKS_MAX : b);
+}
+
+uint64_t system_tasks_max_scale(uint64_t v, uint64_t max) {
+ uint64_t t, m;
+
+ assert(max > 0);
+
+ /* Multiply the system's task value by the fraction v/max. Hence, if max==100 this calculates percentages
+ * relative to the system's maximum number of tasks. Returns UINT64_MAX on overflow. */
+
+ t = system_tasks_max();
+ assert(t > 0);
+
+ m = t * v;
+ if (m / t != v) /* overflow? */
+ return UINT64_MAX;
+
+ return m / max;
+}
+
int update_reboot_parameter_and_warn(const char *param) {
int r;
diff --git a/src/basic/util.h b/src/basic/util.h
index db105197e8..8500c3077c 100644
--- a/src/basic/util.h
+++ b/src/basic/util.h
@@ -186,6 +186,9 @@ int namespace_enter(int pidns_fd, int mntns_fd, int netns_fd, int userns_fd, int
uint64_t physical_memory(void);
uint64_t physical_memory_scale(uint64_t v, uint64_t max);
+uint64_t system_tasks_max(void);
+uint64_t system_tasks_max_scale(uint64_t v, uint64_t max);
+
int update_reboot_parameter_and_warn(const char *param);
int version(void);