Understanding Processor: Processor State
Posted: January 10th, 2009 | Author: TnT Admin | Filed under: Concepts | Tags: processor, Windows | 5 Comments »Processor utilization can be further broken down into time spent executing in user mode (Intel Ring 3) or in privileged mode (Ring 0), two mutually exclusive states. Applications typically run in the more restricted user mode, while operating system functions run in privileged mode. Whenever, an application implicitly or explicitly calls an OS service (e.g. to allocate or free memory, or perform some operation on a file), a context switch occurs as the system transitions from user to privileged mode and back again. The portion of time that a tread is executing in user mode is captured as % User Time; privileged mode execution time is captured in the % Privileged Time counter.
Processor time usage in Windows is broken out into two additional subcategories. % Interrupt Time represents processor cycles consumed in device driver interrupt service routines (ISRs), which process interrupts from attached peripherals such as the keyboard, mouse, disks, network interface card, etc. This is worked performed at very high priority, typically while other interrupts are disabled. It is captured and reported separately not only because of its high priority, but also because it is not easily associated with any particular user process. Windows also tracks the amount of time device drivers spend in deferred procedure calls (DPCs), which also service peripheral devices but run with interrupts enabled. DPCs represent higher-priority work than other system calls and kernel thread activity. Note that % DPC Time is already included in the % Privileged Time measure.
The Scheduler’s thread timing function is notified whenever any context switch occurs, and dutifully records the processing time for the completed function in the appropriate bucket. The context switch might involve going from one user thread to another, a user thread to a kernel function, or a kernel thread to an ISR, followed by a DPC.
(Source: Windows 2000 Performance Guide by Mark Friedman & Odysseas Pentakalos)
Hi, what are things that i have to learn to become a performance test engineer? plz mention the details…..
It’s can’t of hard to really answer your question. It comes with alot of understanding how communication protocol works for me. Secondly, you need to read alot to know how application, web and database servers work in order to find performance problems and tune them. What do you guys think?
I completely agree with TnT Admin.
And one more addition: it will be very difficult for you to be engaged in performance analysis without decent experience of development and/or DB administration.
hai TnT and others,
i am a learner in performance center, we are using LR 8.1, when i contacted HP for upgradation to 9.5, they mentioned that,” if i have one controller i can run on project in Performance center, if i have two controllers i can run 2 projects at a time”..
but i read 3/4 articles related to performance center saying dat, with one controller it self we can run multi projects in Performance center.
could any one let me know which one is correct??
Performance Center depends on how many concurrent load test you can run. Controller numbers should not matter but you will need to know how many concurrent load test that can be run in Performance Center. For LoadRunner, 1 controller can run only 1 load test at one time. There is no concept of concurrent load test in LR, only in PC that concurrent load test feature is available