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Old 08-30-2004, 11:34 PM   #1
mr666white
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Registered: Jun 2004
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Prelink and performance


Ok, I'm sat here watching gentoo compile on one box, and my FC2 box is sat there with the gentoo handbook upen in firefox, and after about 10 hours, i notice the FC2 bos is being rather more sluggish than usual. I fire up KDE system Guard. It tells me that my cpu load is maxed out, and prelink is responsible for a nice 85% of this. Ok so it's niced so it's not really getitng in the way too much, but it's still keeping my FC2 box way to busy.

I sit there for another 3 or 4 hours and prelink is still chugging away quietly. WHY? what the hell is it doing? Is it really beneficial to my system?

Is there a decent reason to keep prelink (which is supposed to help programmes exeute faster) or can i remove it from my system.

At this point i should note that i've got gentoo on a virtually identical box, running much the same software (XFce4, OOO, samba, firefox) but i've not gotten around to thiking about prelink. And the gento box is blisteringly quick compaired to the FC2 box. Both are running 733mhz processors, have 256Mb 133mhz ram, identically set up 40Gb Western digital hds with the same hdparm settings and the transfer rates are virtually identical. Both running reiserfs. Is there some major bloatware bundled into FC2 or is it down to the compiler optimisation (or lack of) in the system?

Help. I like FC2, i don't break it as often, but it's so slow right now!!!
 
Old 08-31-2004, 02:15 AM   #2
realjustin
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FC2 is sort of bloaty in my experience. If you haven't gone into the services and shut down every thing you don't need yet, do so. Other than that, you can try to build a custom kernel, that can help too. I would leave prelink however. The time it's spending there is to prelink the executables. Once it's done, it won't run like that at 98% all the time, it will actually just go away and run whever Fedora has it scheduled to run (I don't know, one a week, month, something). Then the executables will run faster.
 
Old 08-31-2004, 05:54 AM   #3
motub
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Also, if you're looking at the Gentoo Prelink Guide, you'll notice that there are special instructions for informing KDE that it is prelinked, which I believe are valid for any distribution. So don't forget to
Quote:
Set KDE_IS_PRELINKED="true" in /etc/env.d/99kde-env to inform KDE about the prelinking.
I can verify that this really does speed up KDE, when you use it as a full desktop (kdeinit still starts if you try to run a KDE app under another DE, but it's still faster, and it looks like there's not so many instances of kdeinit started as there are when KDE is not prelinked).
 
Old 08-31-2004, 07:24 AM   #4
mr666white
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I come to look at the same box in the morning and I realise I've made a few stupid errors: 1 Prelink was running as a cron job. 2) For some reason prelink is entered into crontab several times. Running at 3am, 4am and 5am. No Idea why as i've not played with cron at all. Plan 1 is to fix crontab to do usefull stuff when i know i'm not going to want to go near the pc: 9am -12midday....

As regards kde and prelinking, if i don't use kde, but use several key kde components (kwrite kopete and k3b) on a daily basis, is prelink going to make a difference for those apps, or just load vast quantities of crap that i don't need running?
 
Old 08-31-2004, 08:20 AM   #5
motub
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Prelink doesn't load any crap whatsoever. Prelink doesn't do anything but load necessary shared libraries into memory so that the programs start faster, which normally would not be done until you started the program.

The programs you refer to are in fact not "key KDE components", but programs that can be integrated with KDE-- in fact, under Gentoo, you can compile K3b at least (I don't use the other two, so I don't know) -kde and -arts and use them even if you don't have KDE installed. Konqueror, on the other hand, is a different story.

Yes, running KDE programs under another DE than KDE is going to load vast quantities of crap (namely kdeinit, and possibly aRTs), but that has nothing to do with prelink, cannot be helped, and in fact prelink does improve the startup time of these programs, and as I said, seems to reduce the number of instances of kdeinit (I use openbox3 normally, but run K3b under it, and the other day, I ran Konq just to see-- I do happen to have KDE installed atm).
 
Old 08-31-2004, 10:21 AM   #6
mr666white
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It's not the gentoo box that's the problem, it's the FC2 box. I've tried disableing prelink and i've noticed some differnces in the performance of the system:

Bigger programmes can take upto twice as long to load on an unladed system.

I'm using a lot less memory to do the same tasks. I'm now happily running open office and firefox (both of which are habitual ram eaters) on the FC2 box without having to use any swap. With prelink running, within half an hour of doing any serious work i'd have at least 100Mb in the swap file. It is currently not using any swap at all.

Large apps (Open office, firefox, the GIMP) all feel more responsive once they're running.

Now i can see the benefit of prelink on a system with ram to spare. I've been looking at a very similar FC2 configuration on a Athalon XP 3000+ system with a gig of ram, and predictably it runs like greased lightning. Tried playing with prelink on that, and it makes a huge difference, most notably whien running kde, less notable when running XFce.

Drawing on my previous experinces with the evils of M$ Windoze XP and it's horriffic implentation of what it calls prefetch. It does a similar job, and for the first few months of installing a system it's damn quick. However there are a lot of people that reinstall XP every 6 months or so to restore performance. Let it be noted however that much the same effect can be achieved by deleteing the prefetch links.

My conclusion is prelink rocks on a fast system with lots of ram.It can make it even faster, but the effects on an obselete junkpile like my collection of servers can be detrimental.
 
  


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