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High/Low profile Memory

Posted: 2011/11/28 05:42:16
by eldo
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]
total used free
Low: 883 139 743
High: 127 127 0
[/code][Moderator edit: Added [i]code[/i] tags to preserve formatting and column labels.]

Thanks,
Eldo

High/Low profile Memory

Posted: 2011/11/30 20:00:11
by pschaff
Seems you only showed a subset of the [i]free[/i] 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]
$ 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[/code]

Re: High/Low profile Memory

Posted: 2011/12/01 03:48:13
by eldo
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

Re: High/Low profile Memory

Posted: 2011/12/01 17:57:02
by pschaff
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".