[THIN] Re: Context Switches

  • From: "Schneider, Chad M." <CMSchneider@xxxxxxxxx>
  • To: "'thin@xxxxxxxxxxxxx'" <thin@xxxxxxxxxxxxx>
  • Date: Wed, 12 Mar 2003 12:22:14 -0600

Pages /sec. @ nothing...
Page Faults/sec. @ 100.


-----Original Message-----
From: Bernd Harzog [mailto:Bernd.Harzog@xxxxxxxxxxx]
Sent: Wednesday, March 12, 2003 12:04 PM
To: thin@xxxxxxxxxxxxx
Subject: [THIN] Re: Context Switches



Let me add my two cents. There are as Ron said two kinds of context
switches. One kind occurs when the processor switches between two user
mode tasks. So, if Ron and I are both running an application on the same
server when the CPU switches between doing work for Ron and work for me,
that causes a context switch. That is a GOOD context switch, because it
is indicative of the CPU doing what it is suppose to do, which is move
so rapidly between doing work for different users that each user never
notices. The second type of context switch occurs when the CPU goes from
user mode to kernel mode, and then back again (two Context Switches).
These are BAD context switches, because when the CPU goes into Kernel
mode it blocks user mode operations and slows everything down.

So, you need to find out what kind of context switches you are getting.
Since MS does not do us the favor of breaking them out, the only way to
find out is to look at other indicators of heavy Kernel Mode operations
and see if they are pegged as well. Try looking at pages/sec and page
faults/sec. If you see a heavy correlation between these and the context
switches you may have an indicator that it is kernel mode related. If it
is, call me, because I have something new that I cannot talk about on
the list that we might want to discuss.

Cheers,

Bernd Harzog
CEO
RTO Software
678-455-5506 x701
bernd@xxxxxxxxxxx
www.rtosoft.com


 -----Original Message-----
From:   Ron Oglesby [mailto:roglesby@xxxxxxxxxxxx]=20
Sent:   Wednesday, March 12, 2003 12:30 PM
To:     thin@xxxxxxxxxxxxx
Subject:        [THIN] Re: Context Switches


Well context switches are really the processor switching between tasks
or going between user mode and kernel mode tasks.

A lot of time I think this can be due to the TYPE of application and
what it does. I have a document imaging/managing software at a client
that will get the context switches up in the 30 - 35,000 range with a
low proc queue and proc utilization at about 60%. This software uses a
tome of different types of databases (SQL, Oracle, and something else)
as different backend servers and is a little graphic intense. The NICs,
Memory, Disk, Proc all are still ok, but every time we get these things
up to 30,000 performance starts to degrade. Now of course this is 30,000
steadily, not spikes. And only 27-30 users on DL 360 G2's
Of course on the same hardware and builds I am hosting Office apps for
like 50 and 60 users with context switches not a problem.

Anyway, haven't found a relief for it yet. Hoping hyper threading has an
effect on this.





Ron Oglesby
Senior Technical Architect
=3D20
RapidApp
Office 312.372.7188
Mobile 312.961.2380
email roglesby@xxxxxxxxxxxx
=3D20


-----Original Message-----
From: Schneider, Chad M. [mailto:CMSchneider@xxxxxxxxx]=3D20
Sent: Wednesday, March 12, 2003 11:20 AM
To: 'thin@xxxxxxxxxxxxx'
Subject: [THIN] Re: Context Switches



I know one really spiked, as the chart now shows the 125,000 marker.

-----Original Message-----
From: Ron Oglesby [mailto:roglesby@xxxxxxxxxxxx]
Sent: Wednesday, March 12, 2003 11:02 AM
To: thin@xxxxxxxxxxxxx
Subject: [THIN] Re: Context Switches



100,000... Cooooool

What type of hardware. DL 360s start to get slow at like 30,000

Ron Oglesby
Senior Technical Architect
=3D3D20
RapidApp
Office 312.372.7188
Mobile 312.961.2380
email roglesby@xxxxxxxxxxxx
=3D3D20


-----Original Message-----
From: Schneider, Chad M. [mailto:CMSchneider@xxxxxxxxx]=3D3D20
Sent: Wednesday, March 12, 2003 10:50 AM
To: 'thin@xxxxxxxxxxxxx'
Subject: [THIN] Context Switches



Any way to tell which app/apps are causing my large context switch
usage?

My servers run high all day, some spikes over 100,000.

Chad M. Schneider
Technology Analyst II
Curwood, Inc.
Phone: 920-303-7609
Pager: 920-909-7609


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Get 30-40% more users per server to save $$$ and time. 
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