12-15-2018
Quote:
Originally Posted by
javanoob
Back to the reason on the post
- I have 3GB of swap disk used (in swap -l)
- I have 10GB+ of free physical RAM
- I have 0 scanrate and vmstat available swap = 37GB
Since i am 10G of physical ram and 0 SR - i am not short on ram
Since i have 37GB of virtual swap available - i am not short on virtual swap
What could have contributed to the 3GB swap disk ?
Three gigabytes of memory were used (i.e. read/written) sometime in the past by some process(es). They have not been accessed for a while so the kernel decided to put the data on disk, to keep the free RAM high.
Quote:
Could it be at some point of time, i am running low on physical ram and swap/paging need to be done ?
You need not to starve on RAM for paging to occur.
Quote:
When does physical space used in swapdisk be release ?
When the processes owning it will die.
Quote:
It is gradually increasing (slow.. but like 5-10MB more of swapdisk used per week) - that is the worrying part.
That might be just some optimization done by the kernel.
There might be a memory leak in a process, 10 MB per week is not among the fiercest ones.
There might be a growing file in /tmp or any tmpfs based file system. The storage area of tmpfs is virtual memory (not any process virtual memory but the OS virtual memory, i.e. RAM + SWAP as Bakunin wrote).
Note also the free memory might be actually used by the kernel, which isn't constrained by process virtual memory rules.
Solaris uses free memory as UFS and NFS cache, so this free memory contains actual data, but it is nevertheless reported as free by vmstat and similar commands, because it is immediately available for processes allocations.
Last edited by jlliagre; 12-15-2018 at 06:36 PM..
This User Gave Thanks to jlliagre For This Post:
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swapon(2) System Calls Manual swapon(2)
NAME
swapon() - add swap space for interleaved paging and swapping
SYNOPSIS
Remarks
The ANSI C "" construct denotes a variable length argument list whose optional and required members are given in the associated comment
DESCRIPTION
The system call makes a block device or a directory named path available to the system for paging and swapping.
priority indicates the order in which the swap space from the device or file system is used. It has a range of 0 (highest) to 10 (lowest).
Space is taken from the lower-numbered systems first.
can be used only by users who have appropriate privileges.
If path names a block device file
makes it available to the system at the specified priority for allocation for paging and swapping.
In this form, takes only two arguments: the path to the block device file, and the priority.
The device associated with path can be a device already known to the system, defined at system configuration time, or it can be a previ-
ously unspecified device.
If the device was already defined at system configuration time and also has a start and/or size defined for that swap device, these values
are used.
Otherwise, if a filesystem exists on the device, swap is added following the filesystem, or if no filesystem exists, the complete device is
used for swap.
See the appropriate system administrator's manual for information on how the size of the swap area is calculated.
If path names a directory
makes the blocks on the file system rooted at path available for paging and swapping.
The min, limit, and reserve arguments are passed and used only if the path argument names a directory.
min indicates the number of file system blocks to take from the file system when is called.
limit indicates the maximum number of file system blocks the swap system is allowed to take from the file system.
reserve indicates the number of file system blocks that are saved for file system use only.
For a pre-existing directory swap, a value of -1 for min, limit, reserve, or priority will keep the value unchanged. This can be used to
change selective values without affecting others. For example, if priority of a pre-existing directory swap needs to be changed without
affecting the values of min, limit, or reserve, one can specify the new priority value and pass -1 for other arguments.
The size for the file system blocks mentioned above is the preferred file system block size. The preferred file system block size can be
obtained by the call. The value of min, limit, or reserve is rounded up to the tunable size.
ERRORS
If fails, is set to one of the following values.
A component of the path prefix denies search permission.
One of priority, min, limit, or reserve arguments is invalid.
The device associated with
path already has swap turned on.
The device associated with
path is already in use.
The device associated with
path was specified at system configuration time to add swap at a specified location, but that location is within an
existing file system on the device.
The LIF header on the device associated with
path contains inconsistent directory data.
Unable to read the device associated with
path.
Too many symbolic links were encountered in translating the path name.
The length of the specified path name exceeds
bytes, or the length of a component of the path name exceeds bytes while is in effect.
The device associated with
path does not exist.
The system-imposed limit on the number of swap file entries has been reached.
There is is not enough available space
on the specified file system or device.
The device associated with
path was specified at system configuration time to add swap following the file system, but no file system was found.
The path argument is not a block special file or the root directory of a file system.
A component of the path is not a directory.
The device associated with
path could not be opened.
The effective user ID is not a user with appropriate privileges.
The device associated with
path is read-only.
WARNINGS
On systems running VxVM 3.5, the swap volumes to be configured for system crash dumps should be created with the usage type as during the
creation of the swap volume. Not doing so will cause a dump corruption. You could use the option of to do the same.
No means is available to stop swapping to a device.
The system allocates no less than the amount specified in min. However, to make the most efficient use of space, more than the amount
requested might be taken from the file system. The actual amount taken will not exceed the number of file system blocks indicated in
reserve.
Swapping to a file system is usually slower than swapping to a device.
Once file system blocks have been allocated for swap space, the file system can not be unmounted unless the system is rebooted.
is the replacement for is to be obsoleted at a future date.
AUTHOR
was developed by the University of California, Berkeley.
SEE ALSO
swapon(1M), vxassist(1M), swapctl(2), privileges(5).
TO BE OBSOLETED swapon(2)