Negative caching
Jay Daniels
jaydanie at gmail.com
Sat Jun 20 02:51:14 UTC 2009
A few years ago while compiling KDE 4.0 on RedHat box, I kept getting
errors. Nobody on the KDE list could explain it. Then during a reboot
one day I got divide overflow. Bad processor. A quick swap verified
the fix.
Although I never had a problem under windows, compiling KDE in Linux put
the processor and memory to the test and revelled a definite problem. I
didn't know what the problem was at the time, but it was a problem non
the least.
jay
Hal Burgiss wrote:
> On Fri, Jun 19, 2009 at 03:24:19AM -0700, Steve Lamb wrote:
>> Hal Burgiss wrote:
>>> I think I've figured out why recent Ubuntu has such abysmal performance. Very
>>> cleverly over a period of time, it takes all the free memory and uses it to
>>> store useless junk that you will never ever use. And then holds on to the
>>> useless stuff as long as it possibly can. And then you are forced to
>>> work out of swap.
>> Uhm... no. Simple as that. Whatever your problem is has no relation to
>> caching or buffers. At least if it is you certainly have quite a further
>> distance to go to prove it than what you've presented in your message. The
>> cached pages, for all intents an purposes, can be considered free. The
>> difference between a cached page and a free page is just a couple of bits in a
>> memory map.
>
> Actually I was trying to blend a little humor with a bad situation that I
> don't fully understand. I have been a Linux only user since Redhat4 (late
> 90's). The last version of windows I owned personally was 3.1. The current
> Ubuntu (desktop) is the poorest performing Linux systems I have experienced in
> that time. On Redhat, I have had desktop X sessions that lasted over a year.
> That is unthinkable now. I am living in terms of weeks, before the system is
> either so slow or slow flaky, a reboot is the best remedy. I have both home
> and work systems on 9.04. And both are problematic. Both ran fine on 8.04. I
> have a number of 8.04 servers that are also fine (but I never run X on
> servers).
>
> [hal at admin1 clients]$ uptime
> 07:58:31 up 353 days, 21:25, 2 users, load average: 0.00, 0.00, 0.00
>
> That's a 8.04 LAMP server that seems to run flawlessly.
>
>> Your speed settings have to the result of something else going on because
>> the caching that the kernel does, if it were the cause, would be evident to
>> more people with heavier usage patterns than you. It is the most commonly
>> maligned function the kernel performs. ;)
>
> I am totally open to other causes/solutions. But what is a better explanation
> of a previously happy system whose performance degrades consistently and
> severely over time? And when left idle for long periods of time, goes
> completely in the toilet, to the point of it taking seconds for windows to
> show any response whatsover to mouse clicks, seconds for keystrokes to appear
> in text terminals, and minutes for new windows to open? A reboot or a restart
> of X will bring back "normal" responsiveness immediately, only to degrade
> again in days/weeks. There is no sign of excessive CPU usage, and no single
> program is taking excessive memory (at least as reported). It seems to have
> all the earmarks of a really wacky swap problem. If not, its doing a good
> imitation of one.
>
> I am also a victim of the intel chipset trainwreck, so that may be a
> complicating factor (on my home system), but doesn't explain a slow,
> consistent degration that eventually makes the system unusuable. The work
> desktop does not degrade as badly and I use compiz effects on that one, so
> that might be another complicating factor there.
>
> Thanks!
>
>
More information about the ubuntu-users
mailing list