8232207: Linux os::available_memory re-reads cgroup configuration on every invocation
Reviewed-by: bobv, sgehwolf
--- a/src/hotspot/os/linux/osContainer_linux.cpp Thu Oct 17 00:00:13 2019 +0200
+++ b/src/hotspot/os/linux/osContainer_linux.cpp Thu Oct 17 00:19:02 2019 +0200
@@ -131,14 +131,34 @@
* hierarchy. If set to true consider also memory.stat
* file if everything else seems unlimited */
bool _uses_mem_hierarchy;
+ volatile jlong _memory_limit_in_bytes;
+ volatile jlong _next_check_counter;
public:
CgroupMemorySubsystem(char *root, char *mountpoint) : CgroupSubsystem::CgroupSubsystem(root, mountpoint) {
_uses_mem_hierarchy = false;
+ _memory_limit_in_bytes = -1;
+ _next_check_counter = min_jlong;
+
}
bool is_hierarchical() { return _uses_mem_hierarchy; }
void set_hierarchical(bool value) { _uses_mem_hierarchy = value; }
+
+ bool should_check_memory_limit() {
+ return os::elapsed_counter() > _next_check_counter;
+ }
+ jlong memory_limit_in_bytes() { return _memory_limit_in_bytes; }
+ void set_memory_limit_in_bytes(jlong value) {
+ _memory_limit_in_bytes = value;
+ // max memory limit is unlikely to change, but we want to remain
+ // responsive to configuration changes. A very short (20ms) grace time
+ // between re-read avoids excessive overhead during startup without
+ // significantly reducing the VMs ability to promptly react to reduced
+ // memory availability
+ _next_check_counter = os::elapsed_counter() + (NANOSECS_PER_SEC/50);
+ }
+
};
CgroupMemorySubsystem* memory = NULL;
@@ -461,6 +481,16 @@
* OSCONTAINER_ERROR for not supported
*/
jlong OSContainer::memory_limit_in_bytes() {
+ if (!memory->should_check_memory_limit()) {
+ return memory->memory_limit_in_bytes();
+ }
+ jlong memory_limit = read_memory_limit_in_bytes();
+ // Update CgroupMemorySubsystem to avoid re-reading container settings too often
+ memory->set_memory_limit_in_bytes(memory_limit);
+ return memory_limit;
+}
+
+jlong OSContainer::read_memory_limit_in_bytes() {
GET_CONTAINER_INFO(julong, memory, "/memory.limit_in_bytes",
"Memory Limit is: " JULONG_FORMAT, JULONG_FORMAT, memlimit);
--- a/src/hotspot/os/linux/osContainer_linux.hpp Thu Oct 17 00:00:13 2019 +0200
+++ b/src/hotspot/os/linux/osContainer_linux.hpp Thu Oct 17 00:19:02 2019 +0200
@@ -36,6 +36,7 @@
private:
static bool _is_initialized;
static bool _is_containerized;
+ static jlong read_memory_limit_in_bytes();
public:
static void init();