Re: [gentoo-user] KDE ridiculous memory usage

[Florian Philipp]

Am 19.09.2010 10:25, schrieb Alan McKinnon:
[...]
> Like I posted in another thread today, the memory columns in top do not mean
> what most people think they mean, nor are they simplistic.
>
> The columns tell you the amount of memory that process can access. This is
> vitally important to understand. Modern memory managers in all OSes have the
> concept of shared code and shared memory. It would be insanely wasteful for
> each process to have it's own copy of all the data in RAM it ever uses. At a
> minimum, every process would need a full copy of glibc loaded into RAM.
>
> Here's what really happens (simplistic version):
>
> An app loads, and links to libraries it needs. They may or may not already be
> in RAM; if nor, they are loaded. Those binary images increase the amount of
> RAM the process may address. The app uses more RAM for it's own purposes (data
> it is using) and after a while lots of that data is still in RAM but no longer
> being used.
>
> When things get tight, the kernel has a good long hard look at memory usage
> and starts chucking bits away that can be dispensed with safely. How much
> control do you, the user, have over this: none whatsoever. Why: because the
> situation is changing millions of times a second and there's no way you can
> keep up.
>
> It's like your heart. You don't actually want to be bothered keeping the damn
> thing pumping consciously. So you let your brain stem do all that heavy
> lifting. With memory, the kernel is your brain stem.
>
> Your numbers above look perfectly normal. Most of that RAM can and will be
> dumped when something else comes along that needs it. The clincher is your
> swap usage. After 8 days you are using only about 12% of total which indicates
> the kernel is quite happily keeping everything under control and still has
> plenty of wiggle room left to keep you humming along nicely.
>
> The only point where this memory scheme goes wrong is when an app has a memory
> leak - it has finished with some data in RAM and does not release it. The
> chances that all your "memory hogs" all have leaks like this are very small.
>
> Final conclusion: you have nothing to worry about.
>

I disagree on that last point. While it might be true that some of the
statistics are not correct, I have a feeling that it is not acceptable
or normal that a simple desktop system is not able to free enough memory
to have more that 1/8 of it available for cache.

I mean, my old system had 2 GB RAM and an equivalent Gnome system on it.
It needed swap as well due to Firefox and Eclipse eating memory. But
otherwise its usage was far less than what I see here.