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Memory Object
The Memory performance object consists of counters that describe the behavior
of physical and virtual memory on the computer. Physical memory is the amount
of random access memory on the computer. Virtual memory consists of space in
physical memory and on disk. Many of the memory counters monitor paging, which is
the movement of pages of code and data between disk and physical memory.
Excessive paging, a symptom of a memory shortage, can cause delays which interfere
will all system processes.
Available Bytes
Available Bytes is the amount of physical memory available to processes
running on the computer, in bytes. It is calculated by summing space on the Zeroed,
Free, and Standby memory lists. Free memory is ready for use; Zeroed memory is
pages of memory filled with zeros to prevent later processes from seeing data
used by a previous process. Standby memory is memory removed from a process's
working set (its physical memory) on route to disk, but is still available to be
recalled.
Detail Level: Expert
Counter Type: PERF_COUNTER_RAWCOUNT
Committed Bytes
Committed Bytes is the amount of committed virtual memory, in bytes.
(Committed memory is physical memory for which space has been reserved on the disk
paging file in case it needs to be written back to disk.)
Detail Level: Expert
Counter Type: PERF_COUNTER_RAWCOUNT
Commit Limit
Commit Limit is the amount of virtual memory that can be committed without
having to extend the paging file(s). It is measured in bytes. (Committed memory is
physical memory for which space has been reserved on the disk paging files.
There can be one paging file on each physical drive.)If the paging file(s) are be
expanded, this limit increases accordingly.
Detail Level: Wizard
Counter Type: PERF_COUNTER_RAWCOUNT
Page Faults/sec
Page Faults/sec is overall rate at which of faulted pages are handled by the
processor. It is measured in numbers of pages faulted. A page fault occurs when
a process requires code or data that is not in its working set (its space in
physical memory) in main memory. This counter includes both hard faults (those
that require disk access) and soft faults (where the faulted page is found
elsewhere in physical memory.) Most processors can handle large numbers of soft
faults without consequence. However, hard faults can cause significant delays.
Detail Level: Novice
Counter Type: PERF_COUNTER_COUNTER
Write Copies/sec
Write Copies/sec is the number of page faults caused by attempts to write that
have been satisfied by coping of the page from elsewhere in physical memory.
This is an economical way of sharing data since pages are only copied when they
are written to; otherwise, the page is shared. This counter counts the number
of copies, without regard for the number of pages copied in each operation.
Detail Level: Wizard
Counter Type: PERF_COUNTER_COUNTER
Transition Faults/sec
Transition Faults/sec is the number of page faults resolved by recovering
pages that were on the modified page list, on the standby list, or being written to
disk at the time of the page fault. The pages were recovered without
additional disk activity. Transition faults are counted in numbers of faults, without
regard for the number of pages faulted in each operation.
Detail Level: Wizard
Counter Type: PERF_COUNTER_COUNTER
Cache Faults/sec
Cache Faults/sec is the number of faults which occur when a page sought in the
file system cache is not found there and must be retrieved from elsewhere in
memory (a soft fault) or from disk (a hard fault). The file system cache is an
area of physical memory that stores recently used pages of data for
applications. Cache activity is a reliable indicator of most application I/O operations.
This counter counts the number of faults, without regard for the number of pages
faulted in each operation.
Detail Level: Wizard
Counter Type: PERF_COUNTER_COUNTER
Demand Zero Faults/sec
Demand Zero Faults/sec is the number of page faults that require a zeroed page
to satisfy the fault. Zeroed pages, pages emptied of previously stored data
and filled with zeros, are a security feature of Windows NT. They prevent
processes from seeing data stored by earlier processes that used the memory space.
Windows NT maintains a list of zeroed pages to accelerate this process. This
counter counts numbers of faults, without regard to the numbers of pages retrieved
to satisfy the fault.
Detail Level: Wizard
Counter Type: PERF_COUNTER_COUNTER
Pages/sec
Pages/sec is the number of pages read from or written to disk to resolve hard
page faults. (Hard page faults occur when a process requires code or data that
is not in its working set or elsewhere in physical memory, and must be
retrieved from disk.) This counter was designed as 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. It is counted in numbers of pages, so it can be
compared to other counts of pages, such as Memory: Page Faults/sec, without
conversion. It includes pages retrieved to satisfy faults in the file system cache
(usually requested by applications) non-cached mapped memory files.
Detail Level: Novice
Counter Type: PERF_COUNTER_COUNTER
Pages Input/sec
Pages Input/sec is the number of pages read from disk to resolve hard page
faults. (Hard page faults occur when a process requires code or data that is not
in its working set or elsewhere in physical memory, and must be retrieved from
disk.) This counter was designed as a primary indicator of the kinds of faults
that cause system-wide delays. It includes pages retrieved to satisfy faults in
the file system cache (usually requested by applications) and in non-cached
mapped memory files. This counter counts numbers of pages, and can be compared to
other counts of pages, such as Memory: Page Faults/sec, without conversion.
Detail Level: Novice
Counter Type: PERF_COUNTER_COUNTER
Page Reads/sec
Page Reads/sec is the number of times the disk was read to resolve hard page
faults. (Hard page faults occur when a process requires code or data that is not
in its working set or elsewhere in physical memory, and must be retrieved from
disk.) This counter was designed as a primary indicator of the kinds of faults
that cause system-wide delays. It includes reads to satisfy faults in the file
system cache (usually requested by applications) and in non-cached mapped
memory files. This counter counts numbers of read operations, without regard to the
numbers of pages retrieved by each operation.
Detail Level: Expert
Counter Type: PERF_COUNTER_COUNTER
Pages Output/sec
Pages Output/sec is the number of pages written to disk to free up space in
physical memory. Pages are written back to disk only if they are changed in
physical memory, so they are likely to hold data, not code. A high rate of pages
output might indicate a memory shortage. Windows NT writes more pages back to disk
to free up space when physical memory is in short supply. This counter counts
numbers of pages, and can be compared to other counts of pages, without
conversion.
Detail Level: Advanced
Counter Type: PERF_COUNTER_COUNTER
Page Writes/sec
Page Writes/sec is the number of times pages were written to disk to free up
space in physical memory. Pages are written to disk only if they are changed
while in physical memory, so they are likely to hold data, not code. This counter
counts write operations, without regard to the number of pages written in each
operation.
Detail Level: Expert
Counter Type: PERF_COUNTER_COUNTER
Pool Paged Bytes
Pool Paged Bytes is the number of bytes in the paged pool, an area of system
memory (physical memory used by the operating system) for objects that can be
written to disk when they are not being used. Memory: Pool Paged Bytes is
calculated differently than Process: Pool Paged Bytes, so it might not equal Process:
Pool Paged Bytes: _Total.
Detail Level: Advanced
Counter Type: PERF_COUNTER_RAWCOUNT
Pool Nonpaged Bytes
Pool Nonpaged Bytes is the number of bytes in the nonpaged pool, an area of
system memory (physical memory used by the operating system) for objects that
cannot be written to disk, but must remain in physical memory as long as they are
allocated. Memory: Pool Nonpaged Bytes is calculated differently than Process:
Pool Nonpaged Bytes, so it might not equal Process: Pool Nonpaged Bytes:
_Total.
Detail Level: Advanced
Counter Type: PERF_COUNTER_RAWCOUNT
Pool Paged Allocs
Pool Paged Allocs is the number of calls to allocate space in the paged pool.
The paged pool is an area of system memory (physical memory used by the
operating system) for objects that can be written to disk when they are not being
used. It is measured in numbers of calls to allocate space, regardless of the
amount of space allocated in each call.
Detail Level: Wizard
Counter Type: PERF_COUNTER_RAWCOUNT
Pool Nonpaged Allocs
Pool Nonpaged Allocs is the number of calls to allocate space in the nonpaged
pool. The nonpaged pool is an area of system memory area for objects that
cannot be written to disk, and must remain in physical memory as long as they are
allocated. It is measured in numbers of calls to allocate space, regardless of
the amount of space allocated in each call.
Detail Level: Wizard
Counter Type: PERF_COUNTER_RAWCOUNT
Free System Page Table Entries
The number of Page Table Entries not currently in use by the system.
Detail Level: Wizard
Counter Type: PERF_COUNTER_RAWCOUNT
Cache Bytes
Cache Bytes is the number of bytes currently being used by the file system
cache. The file system cache is an area of physical memory that stores recently
used pages of data for applications. Windows NT continually adjusts the size of
the cache, making it as large as it can while still preserving the minimum
required number of available bytes for processes.
Detail Level: Advanced
Counter Type: PERF_COUNTER_RAWCOUNT
Cache Bytes Peak
Cache Bytes Peak is the maximum number of bytes used by the file system cache
since the system was last restarted. This might be larger than the current size
of the cache. Cache. The file system cache is an area of physical memory that
stores recently used pages of data for applications. Windows NT continually
adjusts the size of the cache, making it as large as it can while still preserving
the minimum required number of available bytes for processes.
Detail Level: Advanced
Counter Type: PERF_COUNTER_RAWCOUNT
Pool Paged Resident Bytes
Pool Paged Resident Bytes is the current size of paged pool in bytes. The
paged pool is an area of system memory (physical memory used by the operating
system) for objects that can be written to disk when they are not being used. Space
used by the paged and nonpaged pools are taken from physical memory, so a pool
that is too large denies memory space to processes.
Detail Level: Advanced
Counter Type: PERF_COUNTER_RAWCOUNT
System Code Total Bytes
System Code Total Bytes is the number of bytes of pageable operating system
code currently in virtual memory. It is a measure of the amount of physical
memory being used by the operating system that can be written to disk when not in
use. This value is calculated by summing the bytes in Ntoskrnl.exe, Hal.dll, the
boot drivers, and file systems loaded by Ntldr/osloader. This counter does not
include code that must remain in physical memory and cannot be written to disk.
Detail Level: Advanced
Counter Type: PERF_COUNTER_RAWCOUNT
System Code Resident Bytes
System Code Resident Bytes is the number of bytes of operating system code
currently in physical memory that can be written to disk when not in use. This
value is a component of System Code Total Bytes, which also includes operating
system code on disk. System Code Resident Bytes (and System Code Total Bytes) does
not include code that must remain in physical memory and cannot be written to
disk.
Detail Level: Advanced
Counter Type: PERF_COUNTER_RAWCOUNT
System Driver Total Bytes
System Driver Total Bytes is the number of bytes of pageable virtual memory
currently being used by device drivers. (Pageable memory can be written to disk
when it is not being used.) It includes physical memory (Memory: System Driver
Resident Bytes) and code and data written to disk. It is a component of Memory:
System Code Total Bytes.
Detail Level: Advanced
Counter Type: PERF_COUNTER_RAWCOUNT
System Driver Resident Bytes
System Driver Resident Bytes is the number of bytes of pageable physical
memory being used by device drivers. It is the working set (physical memory area) of
the drivers. This value is a component of Memory: System Driver Total Bytes,
which also includes driver memory that has been written to disk. Neither System
Driver Resident Bytes nor System Driver Total Bytes includes memory that cannot
be written to disk.
Detail Level: Advanced
Counter Type: PERF_COUNTER_RAWCOUNT
System Cache Resident Bytes
System Cache Resident Bytes is the number of bytes of pageable operating
system code in the file system cache. This value is a component of Memory: System
Code Resident Bytes which represents all pageable operating system code that is
currently in physical memory.
Detail Level: Advanced
Counter Type: PERF_COUNTER_RAWCOUNT
% Committed Bytes In Use
% Committed Bytes In Use is the ratio of Memory: Committed Bytes to the
Memory: Commit Limit. (Committed memory is physical memory in use for which space has
been reserved in the paging file should it need to be written to disk. The
commit limit is determined by the size of the paging file. If the paging file is
enlarged, the commit limit increases, and the ratio is reduced.)
Detail Level: Expert
Counter Type: PERF_RAW_FRACTION
% Committed Bytes In Use
% Committed Bytes In Use is the ratio of the Committed Bytes to the Commit
Limit. This represents the amount of available virtual memory in use. Note that
the Commit Limit might change if the paging file is extended. This is an
instantaneous value, not an average.
Detail Level: Expert
Counter Type: PERF_RAW_BASE
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