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Full Discussion: %memused is high
Operating Systems Linux Red Hat %memused is high Post 302992353 by jlliagre on Friday 24th of February 2017 05:37:44 AM
Old 02-24-2017
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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lx(5)							Standards, Environments, and Macros						     lx(5)

NAME
lx - Linux branded zone DESCRIPTION
The lx brand uses the branded zones framework described in brands(5) to enable Linux binary applications to run unmodified on a machine with a Solaris Operating System kernel. The lx brand includes the tools necessary to install a CentOS 3.x or Red Hat Enterprise Linux 3.x distribution inside a non-global zone. The brand supports the execution of 32-bit Linux applications on x86/x64 machines running the Solaris system in either 32-bit or 64-bit mode. Supported Linux Distributions The lx brand emulates the system call interfaces provided by the Linux 2.4.21 kernel, as modified by Red Hat in the RHEL 3.x distributions. This kernel provides the system call interfaces consumed by the glibc version 2.3.2 released by Red Hat. In addition, the lx brand partially emulates the Linux /dev and /proc interfaces. Configuration and Administration The lx brand supports the whole root non-global zone model. All of the required linux packages are installed into the private file systems of the zone. The zonecfg(1M) utility is used to configure an lx branded zone. Once a branded zone has been installed, that zone's brand cannot be changed or removed. The zoneadm(1M) utility is used to report the zone's brand type and administer the zone. The zlogin(1) utility is used to log in to the zone. Application Support The lx zone only supports user-level Linux applications. You cannot use Linux device drivers, Linux kernel modules, or Linux file systems from inside an lx zone. You cannot add any non-standard Solaris devices to a Linux zone. Any attempt to do so will result in a zone that zonecfg(1M) will refuse to verify. You cannot run Solaris applications inside an lx zone. Solaris debugging tools such as DTrace (see dtrace(1M)) and mdb (see mdb(1)) can be applied to Linux processes executing inside the zone, but the tools themselves must be running in the global zone. Any core files generated are produced in the Solaris format, and such files can only be debugged with Solaris tools. ATTRIBUTES
See attributes(5) for a description of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWlxr, SUNWlxu | +-----------------------------+-----------------------------+ |Interface Stability |Evolving | +-----------------------------+-----------------------------+ SEE ALSO
mdb(1), zlogin(1), zonename(1), dtrace(1M), zoneadm(1M), zonecfg(1M), brands(5), zones(5), lx_systrace(7D) SunOS 5.11 19 Sep 2006 lx(5)
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