FairShare over-limit allowed in scheduler (#25997)

Author: maVovk

ydb/core/kqp/runtime/scheduler/kqp_compute_scheduler_service.cpp

@@ -268,7 +268,9 @@ void TComputeScheduler::UpdateFairShare() {
     }
 
     snapshot->UpdateBottomUp(Root->TotalLimit);
-    snapshot->UpdateTopDown();
+    // We want to allow FairShare to be over Limit.
+    // If you need to change this behaviour change variable's default value
+    snapshot->UpdateTopDown(true);
 
     {
         TWriteGuard lock(Mutex);

ydb/core/kqp/runtime/scheduler/tree/snapshot.cpp

@@ -36,7 +36,7 @@ void TTreeElement::UpdateBottomUp(ui64 totalLimit) {
     Guarantee = Min<ui64>(GetGuarantee(), Demand);
 }
 
-void TTreeElement::UpdateTopDown() {
+void TTreeElement::UpdateTopDown(bool allowFairShareOverlimit) {
     if (IsRoot()) {
         FairShare = Demand;
     }
@@ -69,7 +69,7 @@ void TTreeElement::UpdateTopDown() {
                 child->FairShare = 0;
             }
 
-            child->UpdateTopDown();
+            child->UpdateTopDown(allowFairShareOverlimit);
         });
     }
     // FIFO variant (when children are queries)
@@ -80,13 +80,15 @@ void TTreeElement::UpdateTopDown() {
 
         // Give at least 1 fair-share for each demanding child
         ForEachChild<TTreeElement>([&](TTreeElement* child, size_t) -> bool {
-            if (leftFairShare == 0) {
+            if (!allowFairShareOverlimit && leftFairShare == 0) {
                 return true;
             }
 
             if (child->Demand > 0) {
                 child->FairShare = 1;
-                --leftFairShare;
+                if (!allowFairShareOverlimit || leftFairShare > 0) {
+                    --leftFairShare;
+                }
             }
 
             return false;

ydb/core/kqp/runtime/scheduler/tree/snapshot.h

@@ -22,7 +22,7 @@ namespace NKikimr::NKqp::NScheduler::NHdrf::NSnapshot {
 
         virtual void AccountSnapshotDuration(const TDuration& period);
         virtual void UpdateBottomUp(ui64 totalLimit);
-        void UpdateTopDown();
+        void UpdateTopDown(bool allowFairShareOverlimit);
     };
 
     class TQuery : public TTreeElement, public NHdrf::TQuery<ETreeType::SNAPSHOT>, public std::enable_shared_from_this<TQuery> {

ydb/tests/functional/tpc/medium/test_workload_manager.py

@@ -36,11 +36,11 @@ def setup_class(cls) -> None:
         super().setup_class()
 
 
-# class TestClickbenchWMScheduler(wm.TestWorkloadMangerClickbenchComputeScheduler, FunctionalTestBase):
+# class TestClickbenchWMScheduler(wm.TestWorkloadManagerClickbenchComputeScheduler, FunctionalTestBase):
 #     iterations: int = 1
 #     verify_data: bool = False
 #     timeout = 100
-#
+
 #     @classmethod
 #     def setup_class(cls) -> None:
 #         cls.setup_cluster()