sync

DBG - new max memory algo.sql

@@ -0,0 +1,53 @@
+/*
+derived from http://sqlmax.chuvash.eu/
+
+SQL Max Memory = TotalPhyMem - (NumOfSQLThreads * ThreadStackSize) - (1GB * CEILING(NumOfCores/4)) - OS Reserved
+NumOfSQLThreads = 256 + (NumOfProcessors*- 4) * 8 (* If NumOfProcessors > 4, else 0)
+ThreadStackSize = 2MB on x64 or 4 MB on 64-bit (IA64)
+OS Reserved = 20% of total ram for under if system has 15GB. 12.5% for over 20GB
+*/
+DECLARE @totSysMemKb INT;
+DECLARE @NumOfCores INT; 
+DECLARE @NumOfProcessors INT; 
+DECLARE @NumOfSQLThreads INT; 
+DECLARE @isX64 BIT = 1;
+DECLARE @ThreadStackSize INT; 
+DECLARE @osReserved INT; 
+DECLARE @newMaxMem INT; 
+DECLARE @appReserved INT = 4*1024*1024; --memory reserved for other apps on the server in Kb
+
+SELECT @totSysMemKb = [total_physical_memory_kb]
+FROM [sys].[dm_os_sys_memory];
+
+SELECT @NumOfCores = [cpu_count], @NumOfProcessors = [cpu_count] / [hyperthread_ratio]
+FROM [sys].[dm_os_sys_info];
+
+SELECT @isX64 = CHARINDEX('64-bit',CAST(SERVERPROPERTY('Edition') AS VARCHAR(MAX)));
+
+SELECT @ThreadStackSize = CASE WHEN @isX64=1 THEN 4096 ELSE 2048 END;
+
+--force 16 Go, 2 vcpu, 2 cores 
+SELECT @totSysMemKb = 16 * 1024 * 1024, @NumOfProcessors = 2, @NumOfCores = 2
+
+SELECT @NumOfSQLThreads = 256 + (@NumOfProcessors - 4) * 8 * (CASE WHEN @NumOfProcessors >4 THEN @NumOfProcessors ELSE 0 END);
+
+
+SELECT @osReserved = CASE WHEN @totSysMemKb < (20*1024*1024) THEN @totSysMemKb * 0.2 ELSE @totSysMemKb * 0.125 END;
+
+PRINT'
+@totSysMemKb:       '+COALESCE(CAST(@totSysMemKb AS VARCHAR(MAX)),'null')+'
+@NumOfCores:        '+COALESCE(CAST(@NumOfCores AS VARCHAR(MAX)),'null')+'
+@NumOfProcessors:   '+COALESCE(CAST(@NumOfProcessors AS VARCHAR(MAX)),'null')+'
+@NumOfSQLThreads:   '+COALESCE(CAST(@NumOfSQLThreads AS VARCHAR(MAX)),'null')+'
+@isX64:             '+COALESCE(CAST(@isX64 AS VARCHAR(MAX)),'null')+'
+@ThreadStackSize:   '+COALESCE(CAST(@ThreadStackSize AS VARCHAR(MAX)),'null')+'
+@osReserved:        '+COALESCE(CAST(@osReserved AS VARCHAR(MAX)),'null')+'
+@appReserved:       '+COALESCE(CAST(@appReserved AS VARCHAR(MAX)),'null')+'
+';
+SELECT @newMaxMem = @totSysMemKb - (@NumOfSQLThreads * @ThreadStackSize) - ((1* 1024 * 1024) * CEILING(@NumOfCores/4)) - @osReserved - @appReserved;
+
+SELECT 
+    @newMaxMem AS maxMemKb
+    , @newMaxMem / 1024 AS maxMemMb
+    , @newMaxMem / 1024 /1024 AS maxMemGb
+;