High/Low profile Memory

General support questions including new installations

High/Low profile Memory

Postby eldo » 2011/11/28 05:42:16

Hi All,

I wish to know more on the impact of high and low profile memory on server performance. As which shows by free -lm is there any way how we can change this change values?

Code: Select all
             total       used       free
Low:           883        139        743
High:          127        127          0
[Moderator edit: Added code tags to preserve formatting and column labels.]

Thanks,
Eldo
eldo
 
Posts: 54
Joined: 2009/06/29 11:51:51

High/Low profile Memory

Postby pschaff » 2011/11/30 20:00:11

Seems you only showed a subset of the free output, but high/low memory only applies to 32-bit kernels. Low memory is in the kernel's address space, and high memory is in user space. If there is a way to change that short of kernel hacking I don't know about it. The best way to improve performance is to increase the total amount of RAM. Your system seems to be a bit short in that department. A couple of examples:
Code: Select all
$ uname -rmi
2.6.32-131.21.1.el6.i686 i686 i386
$ free -lm
             total       used       free     shared    buffers     cached
Mem:          2023        931       1092          0         58        439
Low:           861        132        728
High:         1161        798        363
-/+ buffers/cache:        432       1590
Swap:         2015          0       2015
-------------------------------------------------------------------------
$ uname -rmi
2.6.32-131.17.1.el6.x86_64 x86_64 x86_64
$ free -lm
             total       used       free     shared    buffers     cached
Mem:         24022       4350      19672          0       1304       1814
Low:         24022       4350      19672
High:            0          0          0
-/+ buffers/cache:       1230      22791
Swap:        26207          0      26207
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Re: High/Low profile Memory

Postby eldo » 2011/12/01 03:48:13

As the example shows (second one), the high memory is zero. Indicates the total ram is allocated for the kernel pages. Here what will be the impact of the user applications.

Low: 24022 4350 19672
High: 0 0 0
eldo
 
Posts: 54
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Re: High/Low profile Memory

Postby pschaff » 2011/12/01 17:57:02

Assuming that is meant to be a question, it does not make sense. That's just the way the x86_64 kernel works. There is no alternative, so no "impact".
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