12-16-2018
Quote:
Originally Posted by
javanoob
Lastly, can i confirm the following one last time
Swap allocated will not be shown swap -l. swap used will be shown in swap -l.
"pages swapped out" and "pages swapped in" eventually ends as -> Current swap_used
No. What i meant was: a process gets (though whatever means,
mmap(),
shmget(), the OS or something else) space in the swap. This space will show up in
swap -l as "used". But from a performance POV you do not want to avoid "used swap", you want to avoid transferring memory pages to and from the swap because the actual act of transferring is what slows the system down. This "act of transferring" pages is either "page in" (a page transferred from swap to memory) or "page out" (a page transferred from emory to swap) and this shows in
vmstat. To extend jiliagres metaphor: if the restaurant in question serves unhealthy food, reserving the table there is not what gets you into trouble, only actually eating there is. So it doesn't help to look at the reservations to discern if someone is in danger or not.
Quote:
Originally Posted by
javanoob
Is there anyway to look into the physical swap area and see what's there and hold by which process ?
Now, this is a good question! I would refer you to the
ps command and - if you are really fearless - the
kdb (kernel debugger) command but the difference between me and jiliagre is that he is a Solaris expert and i am not. (Whatever i told you above is "general UNIX knowledge", not specialised Solaris knowledge). There is maybe some special Solaris way he is a aware of that i am not, so his word will be the last in this matter.
I hope this helps.
bakunin
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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)