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Re: slow hard drives crushing interactivity



On Mon, 24 Jan 2005 18:01:55 -0500, Havoc Pennington wrote:
> On my IBM X31 laptop, the system entirely locks up when there's a lot of
> disk access, some common situations are:
>  - when getting heavily into swap due to a runaway process
>  - when running rpm/yum

Yum == swap access, essentially. It uses enormous amounts of memory while
doing dep resolution.

> I have 512M of physical memory. 

I have 256. Welcome to my hell ;)

Seriously, I use apt these days because it's just not possible to sensibly
run yum without flushing nearly everything in memory to disk. Apt is
rather better behaved with RAM but still not wonderful. RPM does make the
whole system unresponsive while it's installing, but it's fairly fast
and doesn't eat memory.

Interestingly autopackage (collection of shell scripts, essentially) has
the opposite effect. It never makes the system unresponsive but if the
system is under load it runs *much* slower. I guess that is because when
the system is bogged down process creation time goes through the roof so
it's sort of automatically rate limiting.

> Is there any solution (that we can enable by default/automatically, not
> much of a solution otherwise)? Right now it's sort of like running an OS
> without protected memory.

It's probably possible to improve the kernels behaviour under pathological
loads but when a friend was using my laptop which isn't that old I had to
do the following for her:

- Replace OpenOffice with AbiWord.
- Use apt instead of yum for updates, and only when she wasn't using it
- Disable the desktop wallpaper (!)

in order to get memory usage down to an acceptable level. And she didn't
use Evolution.

Another problem is that Firefox/Gecko apparently leaks memory like a
sieve. Try opening a new browser instance, set memory cache to zero (or
something very low) and start opening lots of tabs in a typical web
browsing session. Observe that memory usage never goes down. Why? Not sure.

There are some other really sloppy leaks in FC3 too. Eg somehow I got
spamd enabled (is that the default) and when Evolution filters my inbox
Spam-Assassin ends up using a quarter of my memory. I have the GNOME
applet thingy running and "killall spamd" makes memory usage drop off a
cliff for a few minutes. 

thanks -mike


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