sql-server – 禁用超线程将提高我们的SQL Server安装性能

最近我们将Windows 2008 R2数据库服务器从X5470升级到X5560.理论上,两者的CPU性能非常相似,如果有的话,X5560的速度稍快一些.

但是,SQL Server 2008 R2的性能在过去一天左右相当糟糕,并且CPU使用率相当高.

页面预期寿命很长,我们对页面的缓存命中率几乎达到100％,因此内存不是问题.

当我跑：

SELECT * FROM sys.dm_os_wait_stats 
order by signal_wait_time_ms desc

我有：

wait_type                                                    waiting_tasks_count  wait_time_ms         max_wait_time_ms     signal_wait_time_ms
------------------------------------------------------------ -------------------- -------------------- -------------------- --------------------
XE_TIMER_EVENT                                               115166               2799125790           30165                2799125065
REQUEST_FOR_DEADLOCK_SEARCH                                  559393               2799053973           5180                 2799053973
SOS_SCHEDULER_YIELD                                          152289883            189948844            960                  189756877
CXPACKET                                                     234638389            2383701040           141334               118796827
SLEEP_TASK                                                   170743505            1525669557           1406                 76485386
LATCH_EX                                                     97301008             810738519            1107                 55093884
LOGMGR_QUEUE                                                 16525384             2798527632           20751319             4083713
WRITELOG                                                     16850119             18328365             1193                 2367880
PAGELATCH_EX                                                 13254618             8524515              11263                1670113
ASYNC_NETWORK_IO                                             23954146             6981220              7110                 1475699

(10 row(s) affected)

我也跑了

-- Isolate top waits for server instance since last restart or statistics clear
WITH Waits AS (
   SELECT 
        wait_type,wait_time_ms / 1000. AS [wait_time_s],100. * wait_time_ms / SUM(wait_time_ms) OVER() AS [pct],ROW_NUMBER() OVER(ORDER BY wait_time_ms DESC) AS [rn]
FROM sys.dm_os_wait_stats
WHERE wait_type NOT IN ('CLR_SEMAPHORE','LAZYWRITER_SLEEP','RESOURCE_QUEUE','SLEEP_TASK','SLEEP_SYSTEMTASK','SQLTRACE_BUFFER_FLUSH','WAITFOR','LOGMGR_QUEUE','CHECKPOINT_QUEUE','REQUEST_FOR_DEADLOCK_SEARCH','XE_TIMER_EVENT','BROKER_TO_FLUSH','BROKER_TASK_STOP','CLR_MANUAL_EVENT','CLR_AUTO_EVENT','DISPATCHER_QUEUE_SEMAPHORE','FT_IFTS_SCHEDULER_IDLE_WAIT','XE_DISPATCHER_WAIT','XE_DISPATCHER_JOIN'))

SELECT W1.wait_type,CAST(W1.wait_time_s AS DECIMAL(12,2)) AS wait_time_s,CAST(W1.pct AS DECIMAL(12,2)) AS pct,CAST(SUM(W2.pct) AS DECIMAL(12,2)) AS running_pct
FROM Waits AS W1
INNER JOIN Waits AS W2 ON W2.rn <= W1.rn
GROUP BY W1.rn,W1.wait_type,W1.wait_time_s,W1.pct
HAVING SUM(W2.pct) - W1.pct < 95; -- percentage threshold

得到了

wait_type           wait_time_s     pct  running_pct
CXPACKET              554821.66   65.82        65.82
LATCH_EX              184123.16   21.84        87.66
SOS_SCHEDULER_YIELD    37541.17    4.45        92.11
PAGEIOLATCH_SH         19018.53    2.26        94.37
FT_IFTSHC_MUTEX        14306.05    1.70        96.07

这显示了大量时间同步涉及并行性的查询(高CXPACKET).另外,有趣的是,许多这些问题查询正在多个内核上执行(我们的代码中没有任何MAXDOP提示)

服务器已经超过一天左右没有负载.我们遇到了与查询执行的大量差异,通常许多查询看起来比我们以前的数据库服务器慢,而且CPU非常高.

禁用超线程是否有助于降低CPU使用率并提高吞吐量？

解决方法

我们可以谈论超线程是否应该伤害或改善一般事物的理论(我发现它比服务器上的帮助更容易受伤,所以对于“通用”部署我可能会禁用它),但是有只有一种方法可以确定它是否会对您的具体案例产生影响,而这就是尝试并看到.

（编辑：李大同）

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