[THIN] Re: Context Switches

  • From: "Schneider, Chad M." <CMSchneider@xxxxxxxxx>
  • To: "'thin@xxxxxxxxxxxxx'" <thin@xxxxxxxxxxxxx>
  • Date: Wed, 12 Mar 2003 14:25:44 -0600

Nope.

-----Original Message-----
From: Chris Lynch [mailto:lynch00@xxxxxxx]
Sent: Wednesday, March 12, 2003 2:25 PM
To: thin@xxxxxxxxxxxxx
Subject: [THIN] Re: Context Switches



=20
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

I'm wondering.  Do you guys have Outlook XP installed on these servers?  =
If so, we have a client that is having an issue where Outlook prompts =
the user about it failed to start properly the previous time and to =
start in safe mode.  If the user clicks on no, then the server stops =
responding, causing issues with users logging in, and working on the =
server.  We haven't come up with anything, other than it could be a TS =
Roaming profile issue.

Chris

- -----Original Message-----
From: thin-bounce@xxxxxxxxxxxxx [mailto:thin-bounce@xxxxxxxxxxxxx] On =
Behalf Of Pfeifer, Bruce A MSER:EX
Sent: Wednesday, March 12, 2003 12:04 PM
To: 'thin@xxxxxxxxxxxxx'
Subject: [THIN] Re: Context Switches



What a coincidence that we are having a similar problem to Chad's, over =
the past couple weeks.

In our situation it appears that the context switches go through the =
roof, which cause the Perfmon counters to fail, which then causes IMA to =
hang, then the server stops responding to the farm, users can't login =
and so on.

A couple times we have been able to restart the IMA service but =
unfortunately a few of the other occurrences needed a reboot to clear =
the problem. Normally we see the context switches spike up to 250,000 on =
our ML570 4 way servers, but the spikes do not last long enough to =
trigger an RMS alert. =20
With the recent problem the context switches hit a very steady 120,000 =
and continue.  We have not been able to track down the cause (and are =
not really sure how to trace it).

Looking at the comment re paging from Bernd, I looked at our paging logs =
to find that when the problem occurs the pages/sec drops down to almost =
nothing, the Page file % usage remains normal, % processor time =
increases about 30% and Processor interrupt time remain normal.



- -----Original Message-----
From: Schneider, Chad M. [mailto:CMSchneider@xxxxxxxxx]
Sent: Wednesday, March 12, 2003 11:24 AM
To: 'thin@xxxxxxxxxxxxx'
Subject: [THIN] Re: Context Switches



I will get some revamped numbers tomorrow.

- -----Original Message-----
From: Bernd Harzog [mailto:Bernd.Harzog@xxxxxxxxxxx]
Sent: Wednesday, March 12, 2003 12:51 PM
To: thin@xxxxxxxxxxxxx
Subject: [THIN] Re: Context Switches



Well pages/sec can't be zero if you are getting page faults since page =
faults are a form of page file activity. But that aside, 100 page faults =
a second is a low number and to me indicates that page file activity as =
not the driver of a kernel mode issue if that is what you have. I am =
going to ask some folks around here who know more than I do what a good =
next step might be to see if we can help you out. But, it sounds like a =
user mode issue to me, which means that I do not know what to tell you.

Cheers,

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


 -----Original Message-----
From:   Schneider, Chad M. [mailto:CMSchneider@xxxxxxxxx]=3D20
Sent:   Wednesday, March 12, 2003 1:22 PM
To:     'thin@xxxxxxxxxxxxx'
Subject:        [THIN] Re: Context Switches


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]=3D3D20
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
=3D3D3D20
RapidApp
Office 312.372.7188
Mobile 312.961.2380
email roglesby@xxxxxxxxxxxx
=3D3D3D20


- -----Original Message-----
From: Schneider, Chad M. [mailto:CMSchneider@xxxxxxxxx]=3D3D3D20
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
=3D3D3D3D20
RapidApp
Office 312.372.7188
Mobile 312.961.2380
email roglesby@xxxxxxxxxxxx
=3D3D3D3D20


- -----Original Message-----
From: Schneider, Chad M. [mailto:CMSchneider@xxxxxxxxx]=3D3D3D3D20
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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