Ajuste (tuning) del rendimiento de SQL Server 2008
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The document outlines database performance tuning strategies for SQL Server 2008, focusing on analysis methods for identifying bottlenecks in CPU, memory, and I/O. It discusses various tools and features available in SQL Server 2008 to optimize performance, including resource governor and dynamic management views. The content emphasizes a systematic approach to troubleshooting performance issues, highlighting the need for iterative tuning based on data collected from multiple monitoring tools.
![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](https://image.slidesharecdn.com/sql2008performance-100223151913-phpapp01/85/Ajuste-tuning-del-rendimiento-de-SQL-Server-2008-20-320.jpg)
![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'](https://image.slidesharecdn.com/sql2008performance-100223151913-phpapp01/85/Ajuste-tuning-del-rendimiento-de-SQL-Server-2008-30-320.jpg)
Ajuste (tuning) del rendimiento de SQL Server 2008
- 1. Ing. Eduardo Castro, PhD [email protected] http://ComunidadWindows.org
- 2. 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
- 3. 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
- 4. Performance Tuning Tools I/O Bottleneck CPU Bottleneck Memory Bottleneck
- 5. 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…
- 6. Data Collector & Management Data Warehouse (MDW) Extended Events Activity Monitor New DMVs/DMFs
- 7. 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
- 9. Highly scalable with low overhead Future of SQL tracing
- 10. 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
- 12. 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…
- 13. 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)?
- 14. 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
- 15. File level I/O throughput and disk response time
- 16. Runtime Performance monitoring System Reports What counters to look at?
- 17. 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
- 18. Page I/O waits in Buffer pool WriteLog and LogBuffer waits
- 19. 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
- 20. 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
- 21. 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
- 22. 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
- 24. 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…
- 25. 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)
- 26. 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 %
- 27. 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
- 28. Total CPU waits CPU cycles that did the real work Wait in runnable queue Thread voluntarily yields
- 29. 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
- 30. 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'
- 31. 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
- 32. 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)
- 34. 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,…)
- 35. 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
- 36. 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
- 37. 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
- 38. Query execution waits on memory for sorting, hashing,…
- 39. 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
- 40. sys.dm_os_ring_buffers RING_BUFFER_SCHEDULER_MONITOR RING_BUFFER_RESOURCE_MONITOR RING_BUFFER_OOM RING_BUFFER_MEMORY_BROKER RING_BUFFER_BUFFER_POOL
- 41. 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
- 42. 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
- 44. 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 …
- 46. “Troubleshooting Performance Problems in SQL Server 2008” http://msdn.microsoft.com/en- us/library/dd672789.aspx