[THIN] Re: thread quanta and chkroot.cmd thingy
- From: "Timothy Mangan" <tmangan@xxxxxxxxxxxx>
- To: <thin@xxxxxxxxxxxxx>
- Date: Mon, 15 Sep 2003 19:34:03 -0400
Here is an opinion. It is probably worth what you paid for it.
Changing from background to application mode has the effect of reducing the
quanta allowed for background threads by a factor of three (which is still
twice as long as used in the 2000 professional OS). While the length of a
quanta varies (uni/multi-processor, and hal clock dependent), we are
generally talking about allowing the task to run for a maximum of 180 ms
(background mode) versus 60 ms (application mode) for a typical
multi-processor server. Of course, only a few threads run to their full
quanta limit.
We performed some tests to show responsiveness to typical user actions in
the presence of computational background processing that would run to
quantum. This test is similar to the tests in our white paper on enabling
hyper-threading. We measure the time to complete a fairly common user task
(starting a simple app) and determine the difference between the average
time to complete versus the minimum time. That difference reflects the
average responsiveness delay caused by the CPU bound task. Turning on
application mode reduced this average delay in half. This responsiveness is
what users complain about when they say the system feels slow. While we did
not run a maximum number of users test, I would expect that (unless paging
activity interfered), a server should be able to squeak in an extra user or
more with application mode enabled. Is this a breath-taking? No, there are
far more important things to tune. Is it worth doing? Yes, it might keep
you from buying that extra server for a few more months. There is no
doubting that reasonable minds might vary in opinion.
Confusion occurs in this area due to that it is intentionally poorly
documented, and has often changed quite a bit as new OS's come out. NT and
2000 are very different, and even 2000 Professional and Server have nuances.
I have even seen reference in otherwise excellent books that claim
installing Terminal Services changes this behavior by default (which I
haven't seen -- perhaps this was the case under NT and the new book
revisions didn't catch the change?). By the way, at first glance the 2003
scheduler appears to be very close to 2000 here.
With slower hardware, context switching used to be a concern. With today's
gigahertz plus hardware and crazy optimizations that Intel does, only
out-of-the-ordinary context switching should be a concern. Simply put, four
additional context switches are negligible considering the amount of
instructions that will execute over 180ms.
There are server situations where background mode is appropriate. For
example, the folks at MSC Software run a simulation center, where a typical
task is a complex number crunching exercise that takes from 2 hours to a
full day, even on the very high-end servers they use.
tim
-----Original Message-----
From: thin-bounce@xxxxxxxxxxxxx [mailto:thin-bounce@xxxxxxxxxxxxx] On Behalf
Of Brian Madden
Sent: Monday, September 15, 2003 4:33 PM
To: thin@xxxxxxxxxxxxx
Subject: [THIN] Re: thread quanta and chkroot.cmd thingy
So, after reading all these quanta things, does this setting really make a
difference?
I understand that Tim and/or Kevin are testing to see which setting is
better, but wouldn't it not really matter since an adverse setting would
only be impacted by what an administrator is actively running on the
console?
I would assume that this setting doesn't really matter in the real world?
Brian
Brian Madden
202.302.3657
brian@xxxxxxxxxxxxxxxx
--------
Visit www.brianmadden.com for thin client white papers, books, product
reviews, courseware, and training videos.
-----Original Message-----
From: thin-bounce@xxxxxxxxxxxxx [mailto:thin-bounce@xxxxxxxxxxxxx] On Behalf
Of Timothy Mangan
Sent: Monday, September 15, 2003 1:07 PM
To: thin@xxxxxxxxxxxxx
Subject: [THIN] Re: thread quanta and chkroot.cmd thingy
Simple test. The thread that owns the "foreground window" also gets a
priority boost. You can see this in the performance monitor. Start a
program (I like "regedit" because it only has one thread), bring up
performance monitor: Add counter Thread: Current Priority for the thread(s)
of the application to be tested. You will see the priority increase when
the window had the focus. Works as console of TS session.
tim
-----Original Message-----
From: thin-bounce@xxxxxxxxxxxxx [mailto:thin-bounce@xxxxxxxxxxxxx]
Sent: Monday, September 15, 2003 9:28 AM
To: thin@xxxxxxxxxxxxx
Subject: [THIN] Re: thread quanta and chkroot.cmd thingy
Here is Kevin's response:
His answer has made me curious. I can prove who is right with a small test.
I'll let you know.
Kevin Goodman
CTO
RTO Software
* +1-678-455-5506 x702
6 +1-678-455-5551*
kevin.goodman@xxxxxxxxxxx
Address: 5400 Laurel Springs Pkwy, #108 Suwanee, GA 30024 USA
http://www.rtosoft.com
Bernd Harzog
CEO
RTO Software, Inc.
bernd.harzog@xxxxxxxxxxx
678-455-5506 x701
www.rtosoft.com
-----Original Message-----
From: Ron Oglesby [mailto:roglesby@xxxxxxxxxxxx]
Sent: Monday, September 15, 2003 9:22 AM
To: thin@xxxxxxxxxxxxx
Subject: [THIN] Re: thread quanta and chkroot.cmd thingy
Ok, no I have to allot some time today to test this.
Ron Oglesby
Senior Technical Architect
RapidApp
Office 312.372.7188
Mobile 815.325.7618
email roglesby@xxxxxxxxxxxx
-----Original Message-----
From: Andrew Rogers [mailto:Andrew.Rogers@xxxxxxxxxxxxxxxxxx]
Sent: Monday, September 15, 2003 8:12 AM
To: thin@xxxxxxxxxxxxx
Subject: [THIN] Re: thread quanta and chkroot.cmd thingy
Interesting, RTOSoft vs TMurgent - whos right?
You really know how to ask good questions Brian!! :)
Andrew
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