High Last CPU on SQL 2008 SP1

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High Last CPU on SQL 2008 SP1

MichaelDep

Ten Centuries

Points: 1374
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January 21, 2010 at 1:36 pm

#215754

I have a strange issue. I have three servers that are Dual Quad Core CPU boxes with Windows 2008 and SQL 2008 SP1. All three of these servers have the same issue. CPU 7 (Counting 0-7) is sitting consistently at 80-85%. The other 7 CPU sit consistently at 0-4%. I have two other server single six-core processor with Windows 2008 and SQL2008 SP1 that do not have a single high CPU condition. It is always CPU 7 on all three servers. Bouncing the servers have not had any impact. Setting the CPU affinity in SQL to not use that processor has had no impact. These are dedicated SQL boxes no other applications running besides Virus Scan, Backup Software. Which are corporate standards and are on all out servers. Can anyone point me in a direction to resolve this CPU issue?
Michael Deputy

Viewing 8 posts - 1 through 7 (of 7 total)

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Nicholas Cain SSC-Dedicated Points: 33009 More actions · Answer 1

Any idea whats actually using those CPU cycles on that core?

Shamless self promotion - read my blog http://sirsql.net

MichaelDep Ten Centuries Points: 1374 More actions · Answer 2

That's what I would love to figure out. I have masked SQL to not use that CPU. Task manager shows the system 99% idle, but the last CPU is running between 68 and 90% all the time. Can you point me towards a way to determine what that core is doing?

Thanks,

Ewan Hampson SSCrazy Points: 2780 More actions · Answer 3

I believe AV programs are often designed to target the "last" core available, presumably to keep the remainder available for the work you actually bought the system to do. So masking out the "end" one from SQL Server is a good approach. If the AV is a standard you do not control, you could get your people to check that it is properly configured - not scanning the database files, not performing a full scheduled scan at an inopportune time - even see if it can be temporarily disabled (short-term, with appropriate safeguards!) to see what happens.

Summer90 SSC-Dedicated Points: 32864 More actions · Answer 4

I would agree, process of elimination is the way to go. See if you can shutdown your AV services and disable them and watch to see if that last CPU/CORE is still behaving that way or not. If that is not it start looking at other services. We have a couple of services that do oddball things like Inventorying the servers software. When it does this it consumes alot of CPU.

gene.stebley Old Hand Points: 374 More actions · Answer 5

Sounds like you may have some runaway tasks. Check sys.dm_os_schedulers for cpu_id 7 and the current_tasks_count and sys.dm_os_tasks for task_state, sys.dm_os_waiting_tasks for blocking_session_id etc

MichaelDep Ten Centuries Points: 1374 More actions · Answer 6

I would agree with that, except that it persists through reboot and I have masked that CPU so SQL doesn't use it.

gene.stebley Old Hand Points: 374 More actions · Answer 7

anything in your error logs similar to?

2008-10-10 08:49:14.66 Server * BEGIN STACK DUMP:

2008-10-10 08:49:14.66 Server * 10/10/08 08:49:14 spid 0

2008-10-10 08:49:14.66 Server *

2008-10-10 08:49:14.66 Server * Non-yielding Scheduler

If so the mini dump might contain info to help