Ajuste (tuning) del rendimiento de SQL Server 2008

Ing. Eduardo Castro, PhD ecastro@grupoasesor.net http://ComunidadWindows.org

Session Objectives: Get familiar with database performance tuning tools, especially what SQL Server 2008 offers Understand methodology of database performance bottleneck analysis Learn features/improvements of SQL Server 2008 that help improve performance

Target the most challenging and innovative SQL Server applications 10+ TB DW, 3k/tran/s OLTP, Large 500GB+ Cubes, Competitive migrations, Complex deployments, Server Consolidation (1000+) Invest in large scale, referenceable SQL Server projects across the world Provide SQLCAT technical & project experience Conduct architecture and design reviews covering performance, operation, scalability and availability Offer use of HW lab in Redmond with direct access to SQL Server development team

Performance Tuning Tools I/O Bottleneck CPU Bottleneck Memory Bottleneck

System Performance Monitor (Perfmon) SQL Profiler Trace Dynamic Management Views/Functions DBCC commands SQLDiag (Shipped with SQL 2005/2008) SQLIO, SQLIOSim KernRate Debugging tools (Windbg, DebugDiag,…) More…

Data Collector & Management Data Warehouse (MDW) Extended Events Activity Monitor New DMVs/DMFs

MDW Host MDW Client Workstation Target Server Snapshot Data dcexec.exe Management Studio SSIS Pkgs Cache Collection Set MDW Metadata Files Reports Job Metadata SQL Agent msdb

Time line Navigation control Resource usage

Highly scalable with low overhead Future of SQL tracing

Built-in system_health session select event_session_id, name, startup_state from sys.server_event_sessions Session definition example create event session session_error on server ADD EVENT sqlserver.error_reported (action (sqlserver.sql_text, sqlserver.tsql_stack, sqlserver.client_app_name) where error = 50001) ADD target package0.ring_buffer with (max_dispatch_latency = 1 seconds) go alter event session session_error on server state = start; go

Memory allocation tracking sys.dm_os_memory_brokers sys.dm_os_memory_nodes Reqource Governor sys.dm_resource_governor_configuration sys.dm_resource_governor_resource_pools sys.dm_resource_governor_workload_groups Query performance (hash value for query and plan) sys.dm_exec_query_stats Sys.dm_exec_requests sys.dm_exec_procedure_stats sys.dm_exec_trigger_stats More…

Bottleneck – A point or component of a process where throughput is the slowest. Understanding where time is spent Elapsed Time = Running + Waiting Key is the waiting - what type of wait(s)?

Monitor and identify I/O bottleneck Resource Monitor & Performance Monitor MDW DMV & Extended Events What is driving high I/O load? Inefficient query plan Too much data to read/write Slow I/O subsystem

File level I/O throughput and disk response time

Runtime Performance monitoring System Reports What counters to look at?

Physical Disk Object: Avg. Disk Queue Length Avg. Disk Sec/Read Avg. Disk Sec/Write %Disk Time Disk Transfers/Sec Avg. Disk Bytes/Read Avg. Disk Bytes/Write Disk Read Bytes/Sec Disk Write Bytes/Sec SQL Server Buffer Manager Object: (memory pressure could cause I/O pressure) Buffer Cache hit ratio Page Life Expectancy Checkpoint pages/sec Lazywrites/sec

Page I/O waits in Buffer pool WriteLog and LogBuffer waits

High I/O Latch sys.dm_os_wait_stats Wait Time sys.dm_exec_requests pending/stalled sys.dm_io_pending_io_requests I/O sys.dm_io_virtual_file_stats ERRORLOG This is 15 second delay in IO warnings of I/O completion way too delays slow

sqlos package sqlserver package • async_io_requested • physical_page_read • async_io_completed • physical_page_write • wait_info • file_read • wait_info_external • file_write • long_io_detected 2009-04-13 18:30:10.170 spid5s SQL Server has encountered 1 occurrence(s) of I/O requests taking longer than 15 seconds to complete on file [T:tempdbtemplog.ldf] in database [tempdb] (2). The OS file handle is 0x0000000000000670. The offset of the latest long I/O is: 0x000007eecac000 king longer than 15 seconds to complete on file [e:myslowdb.mdf] in database [myslowdb] (1). The OS file handle is 0x00000438. The offset of the latest long IO is: 0x000000513ce000

Look if there is memory pressure Further narrow down to what queries are generating the I/O workload. Tune these queries. Explore data compression to reduce I/O load Upgrade storage hardware

Compress tables/indexes to reduce database size Compression ratio depends on schema & data distribution (avg 50-60%) Reduce query runtime I/O (increase cpu) Identify compression candidates sp_estimate_data_compression_savings sys.dm_db_index_operational_stats

Sustained %Processor Time > 80% Performance Monitor/Task Manager MDW Server Activity Report DMV & Extended Events What is driving high CPU? Recompilations Cursors Inefficient query plans More…

Resource • Monitor it Live Monitor/Task Manager Performance Monitor • Watch Live or Log Counters counters you like System Data Collector • Formatted Perfmon Reports counter based report Windows Performance • Dig deeper using ETW Toolkit (XPerf)

Processor object: %Privileged Time %Processor Time New in SQL Server 2008 for Resource %User Time Governor feature Process object (SQL Server): %Privileged Time %Processor Time %User Time SQL Server:Workload Group Stats CPU usage % Max request cpu time SQL Server:Resource Pool Stats CPU usage % CPU usage target %

SQL Server:SQL Statistics Batch requests/sec SQL Compilations/sec SQL Re-Compilations/sec SQL Server:Cursor Manager by Type SQL Server:Cursor Manager Total Concurrent processing of multiple cursors could be cpu intensive

Total CPU waits CPU cycles that did the real work Wait in runnable queue Thread voluntarily yields

sys.dm_exec_query_stats Sys.dm_exec_sessions sys.dm_exec_requests sys.dm_exec_procedure_stats Sys.sysprocesses sys.dm_exec_trigger_stats cpu_time cpu_time total_worker_time cpu total_scheduled_tim e total_elapsed_time total_elapsed_time Backward compatibility view Sql_handle/query_h total_elapsed_time query_hash ash

sqlos package sqlserver package •scheduler_monitor_non_yielding_ring_buffer_recorded •sql_statement_completed •spinlock_backoff •sp_statement_completed •Wait_info •cursor_manager_cursor_end •wait_info_external •checkpoint_end Extended Event can track individual statement level events like Profiler does with minimal impact - ADD EVENT sqlserver.sql_statement_completed (action (sqlserver.sql_text) WHERE duration > 0), ADD EVENT sqlserver.sp_statement_completed (action (sqlserver.sql_text) WHERE duration > 0) select top 10 CONVERT(xml, event_data).value('(/event/data/value)[4]','int') as 'cpu'

High cpu doesn’t necessarily mean it’s a problem. Drill down to specific workload and queries that drive cpu usage. Tune them. Use Resource Governor to protect high priority workloads Upgrade hardware

Resource Governor allocate cpu/memory to prioritized workloads based on connection string parameters Mixed workloads: OLTP, Reporting, Maintenance Soft Numa Node configuration (soft numa node and cpu affinity) Network Configuration (soft numa node and tcp port)

Monitor and identify memory pressure Performance Monitor/Task Manager MDW Server Activity Report DMV & Extended Events What is eating up my memory? External or internal memory pressure Inefficient query plan (hashing, sorting,…)

AWE 32-bit uses AWE to cache data/index pages 64-bit uses AWE to implement “Locked pages in memory” Environment Virtual Address Max physical Space memory 32-bit on 32-bit OS 2 GB 64 GB 32-bit on 64-bit OS (Wow) 4 GB 64 GB 64-bit on 64-bit OS 8 TB 2 TB

Perfmon is golden tool to identify memory pressure Memory object: Available K/M bytes Commit Limit Paging File %Usage (Peak) Page reads/sec Process object: Private bytes Virtual bytes Working set

SQL Server Memory Manager object: Connection Memory Lock Memory Somebody is waiting on Optimizer Memory memory Memory Grants Pending … SQL Server Buffer Manager object: Buffer cache hit ratio Checkpoint pages/sec Free list stalls/sec Free pages Lazy writes/sec Page life expectancy How long will the page Stolen pages live? Target pages Total pages SQL Server Plan Cache object SQL Server Resource Pool Stats object

Query execution waits on memory for sorting, hashing,…

DBCC MEMORYSTATUS sys.dm_os_sys_memory system_memory_state_desc a good indicator of available physical memory sys.dm_os_process_memory process_physical_memory_low = 1 indicates low physical memory. memory_utilization_percentage value below 100% indicates external memory pressure. sys.dm_os_memory_clerks

sys.dm_os_ring_buffers RING_BUFFER_SCHEDULER_MONITOR RING_BUFFER_RESOURCE_MONITOR RING_BUFFER_OOM RING_BUFFER_MEMORY_BROKER RING_BUFFER_BUFFER_POOL

sqlos package sqlserver package • page_heap_memory_allocated • sort_memory_grant_adjustment • page_heap_memory_freed • plan_cache_cache_hit • memory_node_oom_ring_buffer_recorded • plan_cache_cache_attempt • cursor_manager_cursor_memory_usage 2009-04-14 09:27:15.43 spid62 Failed allocate pages: FAIL_PAGE_ALLOCATION 1

Check memory configuration – sp_configure External memory pressure – Identify what other processes are competing Internal memory pressure – Identify which SQL component is main consumer Workload/query tuning (sorting, hash join…) Resource Governor Hardware upgrade

Focus on methodology – no guess Correlate data points from multiple tools Performance tuning is iterative process – bottleneck could move Resource contention impacts each other Lack of memory -> high cpu & I/O Slow I/O -> tempdb contention …

Ing. Eduardo Castro, PhD ecastro@grupoasesor.net

“Troubleshooting Performance Problems in SQL Server 2008” http://msdn.microsoft.com/en- us/library/dd672789.aspx

Ajuste (tuning) del rendimiento de SQL Server 2008

by Eduardo Castro on Feb 23, 2010

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