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Important Memory counters.
- Pages/sec - Values over 10 indicate
thrashing, i.e. excessive paging
- Available Bytes - Values consistently below
4 MB require more RAM
- Committed bytes - Values significantly
higher the total RAM need more RAM
Investigating Disk Paging
Use memory counters that report paging activity to identify
memory shortages resulting in disk bottlenecks. Start by monitoring the memory
counters and working set values. Confirm that hard page faults are occurring using the
Memory\Pages/sec counter.
Counters Explained
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Hard faults
Very slow
Retrieved from disk |
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Soft faults
Slow
Retrieved from memory outside of the working set |
Nanoseconds vs Milliseconds - The memory is
mightier than the disk!
Memory access times is measured in Nanoseconds.
Disk access times in measured in Milliseconds. The difference factor is a
million which means that disk access times are about a million times slower than
memory access. If a memory access results in a hard page fault, the access will
be a million times slower. Excessive hard page faults can result in a system
that thrashes, i.e. almost no useful work gets done. The simple solution is to
ensure sufficient memory to avoid hard page faults.
If hard page faults are occurring, monitor disk counters to
assess how the disk is behaving during paging: whether it is busy with other
work or with handling page faults. Monitor disk paging using the following steps
and associated counters:
- To confirm hard page faulting use the following Memory and
Process counters:
- Memory\Pages/sec
- Process (All_processes) \Working Set
- Memory\Pages Input/sec
- Memory\Pages Output/sec
- To understand the impact of page faulting on the disk,
compare the number of reads and read bytes measured by the following counters:
- Memory\Page Reads/sec
- PhysicalDisk\Disk Reads/sec
- PhysicalDisk\Avg. Disk Read Bytes/sec
|
Counter |
Description |
| Page Faults/sec |
the average number of pages
faulted per second. This counter includes both hard faults (those that
require disk access) and soft faults (where the faulted page is found
elsewhere in physical memory.) |
| Pages Input/sec |
the rate at which pages are
read from disk to resolve hard page faults. Hard page faults occur when a
process refers to a page in virtual memory that is not in its working set or
elsewhere in physical memory, and must be retrieved from disk. When a page
is faulted, the system tries to read multiple contiguous pages into memory
to maximize the benefit of the read operation. |
| Pages/sec |
the rate at which pages are
read from or written to disk to resolve hard page faults. This counter is a
primary indicator of the kinds of faults that cause system-wide delays. It
is the sum of Memory\\Pages Input/sec and Memory\\Pages Output/sec. |
Hint!
 Optimize memory by stopping
unused services. i.e. Don't run programs that you don't need!
Because services run in the background, they are often forgotten.
Counters for Analyzing Memory Usage
|
To monitor for |
Use this Object\Counter |
| Memory shortages |
Memory\Available Bytes or
Available KBytes or Available MBytes
Process (All_processes)\Working Set
Memory\Pages/sec
Memory\Cache Bytes |
| Frequent hard page faults |
Memory\Pages/sec
Process (All_processes) \Working Set
Memory\Pages Input/sec
Memory\Pages Output/sec |
| Excess paging with a disk
bottleneck |
Memory\Page Reads/sec
Physical Disk\Avg. Disk Bytes/Read |
| Paging file fragmentation |
PhysicalDisk\Split IOs\sec
PhysicalDisk\% Disk Read Time
PhysicalDisk\Current Disk Queue Length
Process\Handle Count |
Memory leaks; memory-intensive
applications
|
Memory\Pool Nonpaged
Allocations
Memory\Pool Nonpaged Bytes
Memory\Pool Paged Bytes
Process(process_name)\Pool Nonpaged Bytes
Process(process_name)\Handle Count
Process(process_name)\Pool Paged Bytes
Process(process_name)\Virtual Bytes
Process(process_name)\Private Bytes |
Cache Manager efficiency
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Cache\Copy Read Hits %
Cache\Copy Reads/sec
Cache\Data Map Hits %
Cache\Data Maps/sec
Cache\MDL Read Hits %
Cache\MDL Reads/sec
Cache\Pin Read Hits %
Cache\Pin Reads/sec
To identify cache bottlenecks, use Memory\Pages Input/sec with these
counters. |
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