Meminfo Post: 91427

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Operating Systems Linux Meminfo Post 91427 by Corona688 on Friday 2nd of December 2005 02:44:23 AM

12-02-2005

Registered User

Cache is used by the operating system to store file caches and the like, so it doesn't have to reload a frequently-used file from the hard drive over and over. But "Cache" is effectively free memory. The OS doesn't hold onto it -- if something else needs memory, cache gets thrown out and the memory used for something else. So your server is humming away at 1.5GB memory free at the moment.

That 190MB of swap, though, that is something to worry about. It only eats into swap space when it runs out of real memory; at some point in the past, it must have been at least 190 megabytes in the hole memory-wise. It could have been more -- that 190 megabytes is just the memory that's still in swap, memory in swap usually stays there until something wants it back. And when a computer is eating into it's swap space, things move very slowly.

Is there any way you could log memory and swap usage over a period of time? Something's consuming huge amounts of memory, I would guess, but you can't tell the culprit from a meminfo output.

Corona688

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LEARN ABOUT HPUX

swapmem_on

swapmem_on(5)							     OBSOLETE							     swapmem_on(5)

NAME

       swapmem_on - OBSOLETE kernel tunable parameter

DESCRIPTION

       The tunable is obsolete.  Processes will always be allowed to use pseudo-swap space if it is available.

       In previous versions of HP-UX, system configuration required sufficient physical swap space for the maximum possible number of processes on
       the system.  This is because HP-UX reserves swap space for a process when it is created, to ensure that a running process never needs to be
       killed due to insufficient swap.

       This  was difficult, however, for systems needing gigabytes of swap space with gigabytes of physical memory, and those with workloads where
       the entire load would always be in core.  This tunable was created to allow system swap space to be less than core memory.   To	accomplish
       this,  a  portion  of  physical	memory	is  set aside as "pseudo-swap" space.  While actual swap space is still available, processes still
       reserve all the swap they will need at fork or execute time from the physical device or file system swap.  Once	this  swap  is	completely
       used,  new  processes  do  not  reserve	swap, and each page which would have been swapped to the physical device or file system is instead
       locked in memory and counted as part of the pseudo-swap space.

WARNINGS

       Installation of optional kernel software, from HP or other vendors, may cause changes to tunable  parameter  values.   After  installation,
       some  tunable  parameters may no longer be at the default or recommended values.  For information about the effects of installation on tun-
       able values, consult the documentation for the kernel software being installed.	For information about optional kernel  software  that  was
       factory installed on your system, see at

AUTHOR

       was developed by HP.

							     Tunable Kernel Parameters						     swapmem_on(5)