对HP unix swapinfo -a 中的memory的解释：
HP-UX启动每一个进程，都需要在swap区预留一块和内存一样大小的区域，以防内存不够时作数据交换。当预留的swap区用完时，系统就不能再启动新的进程。比如，系统物理内存是4G，而设置的交换区只有1G，那么可以计算得出大概3G的内存会浪费（Buffer Cache除外，可能有2G浪费）。
swapmen_on的作用，就是让系统创建一个pseudo-swap（伪交换区），大小为系统物理内存的3/4，但是这个伪交换区并不占用任何内存和硬盘资源。只是说，让系统认为，交换区的大小是1+4*3/4=4G，而不是1G，就是说可以启动更多的进程，避免内存的浪费。
一般系统物理内存不大的时候，设置交换区是物理内存的2-4倍，swapmen_on设置为1或0都没什么影响，但是当系统内存很大如8G时，因为swap一般不设为16G-32G，这时开启swapmen_on就很必要了。
附： swapinfo man:
NAME
swapinfo - system swap space information
SYNOPSIS
/etc/swapinfo [-mtadfhqw]
DESCRIPTION
swapinfo prints information about device and file system swap space.
By default, it prints to standard output a two line header as shown
here, followed by one line per swap area:
Kb Kb Kb PCT START/ Kb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
The fields are:
TYPE One of:
dev Swap space residing on a mass storage device,
either outside the file system or consuming some
or all of a raw device. This swap space is either
statically declared in the kernel, or dynamically
added using the swapon command (see swapon(1M)),
often in /etc/rc during system initialization
based on the contents of /etc/checklist.
fs Dynamic swap space available from a file system,
as set by swapon, often as listed in
/etc/checklist.
hold Swap space on hold. This is space not allocated
on any specific device or file system, but
nonetheless held by the kernel for future use ``on
demand'' by existing processes that have not yet
consumed all the swap space they might need. It
cannot be reallocated until those processes
terminate.
Kb AVAIL The total available swap space from the device or file
system, in blocks of 1024 bytes (rounded to nearest whole
block if necessary), including any swap space already in
use. For file system swap areas the value is not
necessarily constant. It is the current blocks used for
swapping, plus the free blocks available to ordinary users
minus RESERVE (but never less than zero). AVAIL is never
more than LIMIT if LIMIT is non-zero.
Kb USED The current number of 1-Kbyte blocks used for swapping
from the device or file system. Device swap areas are
consumed in machine-dependent ``chunks'' larger than one
block (based on the configurable kernel value swchunk; the
Hewlett-Packard Company - 1 - HP-UX Release 9.0: August 1992
swapinfo(1M) swapinfo(1M)
chunk size defaults to 4 Mbytes on Series 700/800 systems
and to 2 Mbytes on Series 300/400 systems). If Kb AVAIL
is not a multiple of the number of blocks in a chunk, the
left over fraction of a chunk is always shown as used,
except on unused swap devices (see below).
Kb FREE The difference between Kb AVAIL and Kb USED.
PCT USED The percentage of capacity in use, based on Kb USED
divided by Kb AVAIL; 100% if Kb AVAIL is zero.
START/LIMIT For device swap areas, this value is the block address on
the mass storage device of the start of the swap area;
except on Series 800 systems, where it is always ``-'',
because Series 800 only swaps to a complete device or
partition. The value is normally 0 for entire swap
devices, or the end of the file system for devices
containing both a file system and swap space.
For file system swap areas, LIMIT is the maximum number of
1-Kbyte blocks available from the file system, the same as
the limit value given to swapon. A file system LIMIT
value of none means there is no fixed limit; all space is
available except that used for files, less the blocks
represented by minfree (see fs(4)) plus RESERVE.
RESERVE For device swap areas, this value is always ``-''. For
file system swap areas, this value is the number of 1-
Kbyte blocks reserved for file system use by ordinary
users, the same as the reserve value given to swapon.
PRI The same as the priority value given to swapon. This
value indicates the order in which space is taken from the
devices and file systems used for swapping. Space is
taken from lower priority swap areas first. priority can
have a value between 0 and (NSWPRI - 1) (normally 10), and
has a default value of 1.
NAME For device swap areas, the block special file name whose
major and minor numbers match the swap device's ID. The
swapinfo command searches /dev for device names first,
then /dev/dsk, then /dev/rdsk. If no matching block
special file is found, swapinfo prints the device ID
(major and minor values), for example, 0,0x0e0200.
For file system swap areas, NAME is the name of a
directory on the file system, as given to swapon.
Because it needs kernel access, swapinfo normally succeeds only for
the super-user. It reports warnings or errors if unable to access
kernel resources such as /dev/mem or /dev/kmem.
# swapinfo -atm
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 8192 0 8192 0% 0 - 1 /dev/vg00/lvol2
dev 8192 0 8192 0% 0 - 1 /dev/vg00/myswap
reserve - 118 -118
memory 3894 774 3120 20%
total 20278 892 19386 4% - 0 -
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