yiguolei commented on code in PR #19256:
URL: https://github.com/apache/doris/pull/19256#discussion_r1185689368
##########
be/src/runtime/memory/mem_tracker.h:
##########
@@ -64,32 +64,39 @@ class MemTracker {
MemCounter() : _current_value(0), _peak_value(0) {}
void add(int64_t delta) {
- _current_value.fetch_add(delta, std::memory_order_relaxed);
- update_peak();
+ auto value = _current_value.fetch_add(delta,
std::memory_order_relaxed) + delta;
+ update_peak(value);
}
void add_no_update_peak(int64_t delta) {
_current_value.fetch_add(delta, std::memory_order_relaxed);
}
bool try_add(int64_t delta, int64_t max) {
- if (UNLIKELY(_current_value.load(std::memory_order_relaxed) +
delta > max))
- return false;
- _current_value.fetch_add(delta, std::memory_order_relaxed);
- update_peak();
+ auto cur_val = _current_value.load(std::memory_order_relaxed);
+ auto new_val = 0;
+ do {
+ new_val = cur_val + delta;
+ if (UNLIKELY(new_val > max)) {
+ return false;
+ }
+ } while (UNLIKELY(!_current_value.compare_exchange_weak(cur_val,
new_val,
+
std::memory_order_relaxed)));
+ update_peak(new_val);
return true;
}
+ void sub(int64_t delta) { _current_value.fetch_sub(delta,
std::memory_order_relaxed); }
+
void set(int64_t v) {
_current_value.store(v, std::memory_order_relaxed);
- update_peak();
+ update_peak(v);
}
- void update_peak() {
- if (_current_value.load(std::memory_order_relaxed) >
- _peak_value.load(std::memory_order_relaxed)) {
-
_peak_value.store(_current_value.load(std::memory_order_relaxed),
- std::memory_order_relaxed);
+ void update_peak(int64_t value) {
+ auto pre_value = _peak_value.load(std::memory_order_relaxed);
Review Comment:
这个在多线程并发的时候，感觉也不对啊，比如
_peak_value = 3,
线程1： value = 10
线程2： value = 20
两个线程同时运行到line 97， 此时他们拿到的都是pre_value = 3， 此时加入线程1 先执行，那么_peak_value 被更新为10；
现成2 执行 line 98 会直接cas 失败，然后返回
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