diff --git a/util/gctuner/memory_limit_tuner.go b/util/gctuner/memory_limit_tuner.go index 9dba1bd0bd546..1679e012579d0 100644 --- a/util/gctuner/memory_limit_tuner.go +++ b/util/gctuner/memory_limit_tuner.go @@ -38,6 +38,9 @@ type memoryLimitTuner struct { nextGCTriggeredByMemoryLimit atomicutil.Bool } +// fallbackPercentage indicates the fallback memory limit percentage when turning. +const fallbackPercentage float64 = 1.1 + // tuning check the memory nextGC and judge whether this GC is trigger by memory limit. // Go runtime ensure that it will be called serially. func (t *memoryLimitTuner) tuning() { @@ -61,7 +64,7 @@ func (t *memoryLimitTuner) tuning() { go func() { memory.MemoryLimitGCLast.Store(time.Now()) memory.MemoryLimitGCTotal.Add(1) - debug.SetMemoryLimit(math.MaxInt64) + debug.SetMemoryLimit(t.calcMemoryLimit(fallbackPercentage)) resetInterval := 1 * time.Minute // Wait 1 minute and set back, to avoid frequent GC failpoint.Inject("testMemoryLimitTuner", func(val failpoint.Value) { if val, ok := val.(bool); val && ok { @@ -69,7 +72,7 @@ func (t *memoryLimitTuner) tuning() { } }) time.Sleep(resetInterval) - debug.SetMemoryLimit(t.calcMemoryLimit()) + debug.SetMemoryLimit(t.calcMemoryLimit(t.GetPercentage())) for !t.waitingReset.CompareAndSwap(true, false) { continue } @@ -106,23 +109,27 @@ func (t *memoryLimitTuner) GetPercentage() float64 { // UpdateMemoryLimit updates the memory limit. // This function should be called when `tidb_server_memory_limit` or `tidb_server_memory_limit_gc_trigger` is modified. func (t *memoryLimitTuner) UpdateMemoryLimit() { - var memoryLimit = t.calcMemoryLimit() + var memoryLimit = t.calcMemoryLimit(t.GetPercentage()) if memoryLimit == math.MaxInt64 { t.isTuning.Store(false) + memoryLimit = initGOMemoryLimitValue } else { t.isTuning.Store(true) } debug.SetMemoryLimit(memoryLimit) } -func (t *memoryLimitTuner) calcMemoryLimit() int64 { - memoryLimit := int64(float64(memory.ServerMemoryLimit.Load()) * t.percentage.Load()) // `tidb_server_memory_limit` * `tidb_server_memory_limit_gc_trigger` +func (*memoryLimitTuner) calcMemoryLimit(percentage float64) int64 { + memoryLimit := int64(float64(memory.ServerMemoryLimit.Load()) * percentage) // `tidb_server_memory_limit` * `tidb_server_memory_limit_gc_trigger` if memoryLimit == 0 { memoryLimit = math.MaxInt64 } return memoryLimit } +var initGOMemoryLimitValue int64 + func init() { + initGOMemoryLimitValue = debug.SetMemoryLimit(-1) GlobalMemoryLimitTuner.Start() } diff --git a/util/gctuner/memory_limit_tuner_test.go b/util/gctuner/memory_limit_tuner_test.go index 47d1d8409d8b5..c6f63215c01dd 100644 --- a/util/gctuner/memory_limit_tuner_test.go +++ b/util/gctuner/memory_limit_tuner_test.go @@ -15,7 +15,6 @@ package gctuner import ( - "math" "runtime" "runtime/debug" "testing" @@ -76,10 +75,9 @@ func TestGlobalMemoryTuner(t *testing.T) { checkNextGCEqualMemoryLimit := func() { runtime.ReadMemStats(r) nextGC := r.NextGC - memoryLimit := GlobalMemoryLimitTuner.calcMemoryLimit() - // In golang source, nextGC = memoryLimit - three parts memory. So check 90%~100% here. + memoryLimit := GlobalMemoryLimitTuner.calcMemoryLimit(GlobalMemoryLimitTuner.GetPercentage()) + // In golang source, nextGC = memoryLimit - three parts memory. require.True(t, nextGC < uint64(memoryLimit)) - require.True(t, nextGC > uint64(memoryLimit)/10*9) } memory600mb := allocator.alloc(600 << 20) @@ -91,7 +89,7 @@ func TestGlobalMemoryTuner(t *testing.T) { require.True(t, gcNum < getNowGCNum()) // Test waiting for reset time.Sleep(500 * time.Millisecond) - require.Equal(t, int64(math.MaxInt64), debug.SetMemoryLimit(-1)) + require.Equal(t, GlobalMemoryLimitTuner.calcMemoryLimit(fallbackPercentage), debug.SetMemoryLimit(-1)) gcNum = getNowGCNum() memory100mb := allocator.alloc(100 << 20) time.Sleep(100 * time.Millisecond) @@ -102,7 +100,7 @@ func TestGlobalMemoryTuner(t *testing.T) { runtime.GC() // Trigger GC in 80% again time.Sleep(500 * time.Millisecond) - require.Equal(t, GlobalMemoryLimitTuner.calcMemoryLimit(), debug.SetMemoryLimit(-1)) + require.Equal(t, GlobalMemoryLimitTuner.calcMemoryLimit(GlobalMemoryLimitTuner.GetPercentage()), debug.SetMemoryLimit(-1)) time.Sleep(100 * time.Millisecond) gcNum = getNowGCNum() checkNextGCEqualMemoryLimit()