Understanding Memory: Virtual Memory shortage alerts

Waiting for the paging file to reach 90% threshold maybe too late, especially on any system configuration with a single paging file. Therefore, the recommendation is to take remedial action long before 90% threshold is reached.

When the systems reaches the 90% threshold, not only are there few available virtual memory slots, what slots are available maybe very scattered, preventing applications from allocating large blocks of virtual storage. When the system is approaching the Commit Limit, applications may begin to fail because they cannot allocate virtual memory. For instance, the system application responsible for sending the warning message to the console and to the event log that the paging file is 90% full sometimes fails because it cannot allocate virtual memory, so you might not even receive notification that the event has occurred. In short, by the time the 90% paging file allocation threshold is reached, it may already be too late to take corrective action. Read the rest of this entry »

Understanding Memory: Performance Concerns

A pervasive concern of virtual memory schemes is that the performance of application programs may suffer when there is a shortage of real memory and too many page faults occur. Windows maintain a pool of available (free) real memory pages to resolve page faults quickly. Whenever the pool is depleted, Windows replenishes its buffer of available RAM by trimming older (less frequently referenced) pages of active processes and by swapping the pages of idle foreground applications to disk. Read the rest of this entry »

Understanding Memory: Page Fault Resolution

For all its virtues, virtual memory can raise some serious performance issues. Among them is execution delays encountered by programs whenever they reference virtual memory locations not in the current set of memory-resident pages. This is known as page fault. A program thread that incurs a page fault is halted during page fault resolution, the time it takes the OS to find the specific page on disk and restore it to real memory.
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Understanding Memory: Virtual Addressing

Virtual memory is a feature supported by most advanced processors. Hardware support for virtual memory includes hardware mechanism to map from logical (virtual) memory address that application programs reference to physical (real) memory hardware addresses.

When an executable program’s image file is first loaded into memory, the logical memory address range of the application is divided into fixed-size chunks called pages. These logical pages are them mapped to similar-sized physical pages that are resident in real memory. Read the rest of this entry »

Monitoring SAP in SilkPerformer

SilkPerformer also offers monitoring solution to SAP during a load test.  However, unlike LoadRunner that depends on SiteScope as an intermediary to monitor SAP, SilkPerformer uses the TCodes (Transaction Code) directly to query the monitoring statistics.  (Refer back to “Monitoring SAP in LoadRunner” for more information on monitoring SAP using LoadRunner).
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