Re: [gentoo-user] Swap performance

[Paul Hartman <paul.hartman+gentoo@gmail.com>]

On Wed, May 25, 2011 at 9:20 AM, Alex Schuster <wonko@wonkology.org> wrote:
> Hi there!
>
> I still wonder why my KDE4 system starts swapping so early. Until a week
> ago, I had 6G of RAM, but after a day of being logged in, I usually had some
> swap usage. Sometimes this goes up to 1.5G, this is when the system becomes
> way too slow and I log out.

I can't remember the last time my swap was used at all. I have 12G of
RAM, but in my prior system with 8G it was the same. Only in a rare
case when some program had run-away memory usage/memory leak did I
ever get to swap usage... I'm using vanilla kernel 2.6.39 with no
patches, no BFS. And I use proprietary nvidia-drivers. I normally
don't have so many programs running at once, but it happens sometimes.

Since 2.6.38 and enabling automatic process grouping, I don't use nice
or ionice at all anymore. I do parallel emerge with -j along with make
-j12 and never notice any slowdown or lag in UI at all.

With KDE4 logged in, and no GUI apps running (other than knutmon and
wicd), my RAM usage is slightly less than 900M (not counting
filesystem caches).

>BTW, does anyone else's kwin use 750M? That's pretty high, I think it used
>to be more like 300M.

My kwin (4.6.3-r1) has currently 507M VIRT, 54M RES, 37M SHR according to top.

My worst memory offenders, by resident memory:
clamd 124M
denyhosts 114M
X 75M
plasma-desktop 56M

By virtual memory:
krunner 964M
wicd-client (python) 681M
plasma-desktop 643M
kded4 581M

>Or I do a 'swapoff -a && swapon -a', this empties the swap and also
>frees memory. But this takes _quite_ _a_ _while_. Once I measured 37 minutes
>to clear 1G of swap.

My PC doesn't swap, but in my Nokia N900, it runs Linux and X, heavy
use of gtk and Qt4 libs, it has 256M of RAM and 768M of swap on eMMC
(transfer rate about 20MB/sec). It swaps like crazy. :) Usually there
is more swap in use than RAM, actually.

When I move the swap to a slow SD card instead (2MB/sec transfer
rate), even in that slow device, swapoff on the eMMC swap partition
with ~500M in-use takes about 2 or 3 minutes at most with the data
being swapped slowly into the SD card.

So I think in your case it should be much faster than that!