======================================== "Fred" wrote...... From: "seskjohor" <seskjohor@xxxxxxxxx> Subject: RMS The Thread Count on our Citrix Server in RMS is flagging RED and I was wondering what is happening and if it is something that needs looking after etc, etc, etc. Please help. Thanks. Fred [Frith] On a Citrix server, "interrupts/sec" (or threads) can reach quite high values due to the input (via ICA) from client-side input devices, including mouse and keyboard activity. To illustrate this, you can artificially generate interrupts by quickly moving a mouse back and forwards, or clicking repeatedly, from an ICA session. [Frith] So what is normal behaviour for "interrupts/sec"? Well, like most processor counters, "interrupts/sec" will normally sit at a fairly regular baseline value and spike intermittently. Quite high spikes for all processor counters are well-tolerated by Microsoft operating systems, but where spikes are sustained there are limits beyond which performance will suffer. In Citrix systems, sustained user load can result in baseline rising for quite prolonged periods of time, and the real test is whether users report poor performance. [Frith] But what is a "high value" for "interrupts/sec"? OK, the reason this is a difficult question is that "interrupts/sec" is an absolute counter (i.e. it is not relative to the speed of the processor), and faster processors (and in particular, later generation processors) can tolerate and continue to performance under much higher "interrupts/sec" than was previously possible. These extracts from TechNet illustrate what is considered tolerable, for various processors, and also shows a trend toward higher "interrupts/sec" being considered acceptable: "On an Intel 486 or later processor, the processor clock interrupts every 10 milliseconds, or 100 times per second. Network interrupts can produce 200-1000 interrupts/sec." "On a Pentium computer, 500 interrupts per second may be normal. A high level can be as many as 1,000 interrupts per second." "This counter should operate continuously between 100 and 1,000, but spikes up to 2,000 are acceptable." "However, if the number of interrupts consistently exceeds 1,000 on a 80486/66-based system, or 3,500 on a Pentium 90 PCI bus system, a hardware error or interrupt conflict with devices may be occurring. " "Depends on processor. Up to 1,000 for 486/66 processors; 3,500 for P90; more than 7,000 for P200. " [Frith] So what level of "interrupts/sec" should I consider problematic, and configure alerts for? In my professional opinion, the TechNet extracts above are illustrative of an increasing acceptance of higher "interrupts/sec", provided that the processor is of later-generation, high-speed capacity. This changing trend is the reason that monitoring utilities such as Resource Management Services frequently ship with unnaturally low alert lines for "interrupts/sec": the utility cannot know what processor the system is running and the counter is an absolute value. In the case of a Pentium III processor in excess of 500 MHz, "interrupts/sec" should not be considered problematic until a value of at least 7,000 is sustained for at least 60 seconds. This consideration is supported by the latest references in TechNet: "Select the Processor: \Interrupts/sec object:counter, and configure an alert to be generated when the value is over 7,000 for 60 seconds." [Frith] I hope this information is helpful to you. Kind regards, Frith Frith Brown MCSE (Win2K), CCEA, CCDA, ASE Engineering Services Manager Computerland New Zealand mailto:frith.brown@xxxxxxxxxxxxxx ========================================