Physical RAM Post: 302621697

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Operating Systems Linux Red Hat Physical RAM Post 302621697 by sds9985 on Tuesday 10th of April 2012 11:35:37 PM

04-11-2012

Registered User

An active RHEL system should be using almost all of the free physical memory for cache and buffers. Once you start doing application I/O, you'll see the memory get "used" by the OS quickly. Remember, the memory "used" for cache/buffers is actually free and the kernel can reclaim it very quickly if memory demand for processes increases. The "free" command shows you the difference between "used" memory with and without including the cache/buffers.

Older versions of Linux did have a penalty for very large memory because the algorithms used to manage memory pages were primitive. Many of those problems were addressed in later RHEL 4 releases and by the time we got to RHEL 5 and 6, those issues have been completely resolved. Many of our servers run 256 or 512GB of RAM. For a BL460c with maybe 8 cores, 32GB seems to me to be about right. If it's a BL460cG6 with 16 cores, 32GB seems small. It all depends on what applications or databases you're running on it.

Here's an example from a mid range system with 48 cores:

Code:

# free -g
           total       used       free     shared    buffers     cached
Mem:           251        250          0          0          0        226
-/+ buffers/cache:         24        226
Swap:          294         20        273

At first glance it looks like this system has no free memory. But the actual memory used by processes is actually only 24GB - the other 226GB is cache/buffers.

With very large amounts of RAM on certain hardware you can encounter NUMA issues, but as a general rule, you can never have too much memory. RHEL will find a way to use it.

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mdbfontencoding

mdbFontEncoding(5)						 The m17n Library						mdbFontEncoding(5)

NAME

       mdbFontEncoding - Font Encoding

DESCRIPTION

       The m17n library loads information about the encoding of each font form the m17n database by the tags <font, encoding>. The data is loaded
       as a plist of this format.

       FONT-ENCODING ::= PER-FONT *

       PER-FONT ::= '(' FONT-SPEC ENCODING [ REPERTORY ] ')'

       FONT-SPEC ::=
	   '(' [ FOUNDRY FAMILY
	      [ WEIGHT [ STYLE [ STRETCH [ ADSTYLE ]]]]]
	    REGISTRY ')'

       ENCODING ::= SYMBOL

       FONT-SPEC is to specify properties of a font. FOUNDRY to REGISTRY are symbols corresponding to Mfoundry to Mregistry property of a font.
       See m17nFont for the meaning of each property.

       For instance, this FONT-SPEC:

	   (nil alice0 lao iso8859-1)

       should be applied to all fonts whose family name is 'alice0 lao', and registry is 'iso8859-1'.

       ENCODING is a symbol representing a charset. A font matching FONT-SPEC supports all characters of the charset, and a character code is
       mapped to the corresponding glyph code of the font by this charset.

       REPERTORY is a symbol representing a charset or 'nil'. Omitting it is the same as specifying ENCODING as REPERTORY. If it is not 'nil', the
       charset specifies the repertory of the font, i.e, which character it supports. Otherwise, whether a specific character is supported by the
       font or not is asked to each font driver.

       For so called Unicode fonts (registry is 'iso10646-1'), it is recommended to specify 'nil' as REPERTORY because such fonts usually supports
       only a subset of Unicode characters.

COPYRIGHT

       Copyright (C) 2001 Information-technology Promotion Agency (IPA)
       Copyright (C) 2001-2011 National Institute of Advanced Industrial Science and Technology (AIST)
       Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License
       <http://www.gnu.org/licenses/fdl.html>.

Version 1.6.2							    12 Jan 2011 						mdbFontEncoding(5)

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