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**jbaerbock** · Jan 20, 2008, 05:36 AM

Re: Memory Hog?

So ok get this, KSysGuard reports 900k mem used. HTop and System Monitor (installed both to crosscheck) report 115k used. So um what the heck? I take it SysGuard is buggy?

**Rog131** · Jan 20, 2008, 06:01 AM

Re: Memory Hog?

Rule of thumb in the Linux: "empty ram is wasted ram"

FAQ Linux Memory Management
http://gentoo-wiki.com/FAQ_Linux_Memory_Management

Overview of memory management

Traditional Unix tools like 'top' often report a surprisingly small amount of free memory after a system has been running for a while. For instance, after about 3 hours of uptime, the machine I'm writing this on reports under 60 MB of free memory, even though I have 512 MB of RAM on the system. Where does it all go?

The biggest place it's being used is in the disk cache, which is currently over 290 MB. This is reported by top as "cached". Cached memory is essentially free, in that it can be replaced quickly if a running (or newly starting) program needs the memory.

The reason Linux uses so much memory for disk cache is because the RAM is wasted if it isn't used. Keeping the cache means that if something needs the same data again, there's a good chance it will still be in the cache in memory. Fetching the information from there is around 1,000 times quicker than getting it from the hard disk. If it's not found in the cache, the hard disk needs to be read anyway, but in that case nothing has been lost in time...

Here:

:~$ free -m
total used free shared buffers cached
Mem: 1011 977 34 0 171 545
-/+ buffers/cache: 260 751
Swap: 2000 0 2000

FREE(1) Linux User’s Manual FREE(1)

NAME
free - Display amount of free and used memory in the system

SYNOPSIS
free [-b | -k | -m | -g] [-o] [-s delay ] [-t] [-V]

DESCRIPTION
free displays the total amount of free and used physical and swap mem‐
ory in the system, as well as the buffers used by the kernel. The
shared memory column should be ignored; it is obsolete.

Options
The -b switch displays the amount of memory in bytes; the -k switch
(set by default) displays it in kilobytes; the -m switch displays it in
megabytes; the -g switch displays it in gigabytes.

If you have free ram, you can try programs like:
Preload

adaptive readahead daemon
preload monitors applications that users run, and by analyzing this
data, predicts what applications users might run, and fetches those
binaries and their dependencies into memory for faster startup times.

Note that installing preload will not make your system boot faster
and that preload is a daemon that runs with root priviledges.

Homepage: http://preload.sourceforge.net/

**jbaerbock** · Jan 20, 2008, 12:03 PM

Re: Memory Hog?

Ah ok good to know. Is there anyway then to calculate how much system resources is taken by Linux vs. Windows?

**dibl** · Jan 20, 2008, 12:59 PM

Re: Memory Hog?

I'll speculate that there is no good way to do a precise direct comparison between the two OSs, because of the fact that there are different services started up by each one, that you can't totally control. To verify this, look at the list of running processes in KSysguard, and then run Windows and look at the list of processes using something like msconfig, and look at the Services tab.

So, probably all you can do is a rough comparison. Start up each one, don't run any apps, and check the average CPU load and memory load over a small period of time like 3 minutes, and draw your conclusions, bearing in mind what Rog131 has pointed out about the Linux memory usage model, which seeks to maximize the utilization of RAM for useful purposes, versus the Windows model in which used RAM is kinda unavailable for the next tasking.

**jbaerbock** · Jan 20, 2008, 02:16 PM

Re: Memory Hog?

Good to know. I'm just glad it isn't a true problem because I love Kubuntu

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