%memused is high Post: 302992353

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Operating Systems Linux Red Hat %memused is high Post 302992353 by jlliagre on Friday 24th of February 2017 05:37:44 AM

02-24-2017

Registered User

Quote:

Originally Posted by MadeInGermany

I hear this over and over again, from the Linux community. Always use 100%, a usage under 100% is wasted RAM, blabla.

This question is asked in the Red Hat forum so there is no doubt the OP is running Linux. The Linux kernel is designed to use all otherwise free RAM as cache with no penalties.

Note that under Unix and Linux, you can't really use 100%, the OS try hard to make sure minfree is left (min_free_kbytes on Linux), although minfree/min_free_kbytes are normally very small compared to the RAM size.

HP-UX might still has an problem freeing buffer cache memory but that's a design issue that should have been fixed if not already. Another System V implementation, Solaris, did it 17 years ago. On Solaris, the cache memory is reported as free memory and is freed almost instantly. See Understanding Memory Allocation and File System Caching in OpenSolaris (Richard McDougall's Weblog)

On the other hand, RAM allocated in kernel buffers, regardless of the OS, is much more difficult to be retrieved for applications so tuning can be useful here, for example when ZFS is used.

Back to the OP issue, he is running on a virtualized environment and has no access to the hypervisor statistics. The hypervisor might well lie about actual resources available to the kernel so anything is possible.

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vzcalc

vzcalc(8)							    Containers								 vzcalc(8)

NAME

       vzcalc - calculate resource usage of a container

SYNOPSIS

       vzcalc [-v] CTID

DESCRIPTION

       This  utility  displays	the  share  of the host system resources a particular container is using. If the container is running, the current
       usage is displayed. High utilization values (>100%) mean the system is overloaded (or the container has an invalid configuration).

       Current
	      Shows the amount of the resources consumed by the container at a given time.

       Promised
	      Shows the resources soft limit values "promised" for a given container.

       Max    Shows the resources hard limit values "promised" for a given container.

       If the -v option is specified, the following additional information is also displayed:

       Low Mem
	      The part of memory residing at lower addresses and directly accessed by the kernel (only makes sense for 32-bit architectures).

       Total RAM
	      Total memory.

       Mem+Swap
	      Amount of memory available for applications (both RAM and swap space).

       Alloc Mem
	      Standard memory allocations made for applications in a container.  This is a more "virtual" system resource  than  RAM  or  RAM  and
	      swap.

       Num. Proc
	      Number of processes.

OPTIONS

       -v     Display additional information.

EXIT STATUS

       Normally, the exit status is 0. On error, the exit status is 1.

LICENSE

       Copyright (C) 2000-2009, Parallels, Inc. Licensed under GNU GPL.

OpenVZ								    10 Dec 2009 							 vzcalc(8)