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How much RAM can ML effectively utilize?


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  • 1 year later...

CloakedPenguin, you sound like me. My obsession with ram comes from my just barely being able to scrape enough money together for 5 MegaBytes of SIMMs, for my old 386DX-40 system I had. It was just barely enough to play MSDOS DOOM and jerkily at that. Those were the days when 1 MB simms cost $70 each and 4 MB ones cost $200 or so each.

 

Now I have 4 x 256 MB DDR333 waiting to be installed in my new mobo and they cost me $30 each! My how times and prices have changed! My mobo can handle 4 GB and Linux Enterprise kernel easily handles that. Any more and a special module has to be enabled for up to 16 GB.

 

The standard kernel only has support enabled for up to 868 MB.

 

No such thing as too much memory. :D

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Actually the HIMEM switches in the kernel are either 4GB or 16GB.

I Don't know where 2GB is coming from....

 

The real question is HOW DO YOU USE YOUR RAM.

I have a GIG in my main PC and if i leave it doing nothing it won't take much.

 

As keeps being pointed out the KDE thing is really moot. As you open more apps in KDe it uses incrementally LESS memory than openiong a whole Gtk app seperately.

 

If you wanna use evolution then pack in the memory...

 

While your at it try this:

Stick in 64MB and rip a wav to mp3 at the console.

It takes ages....becuase its writing to/from swap.

Now stick in MORE than the WAV + MP3 + kernel + bladeenc or whatever and it takes no time at all. (at least not ling enough to bother timing.... )

 

Personally I think IF you EVER use SWAP (more than occaisionally then your time must be free) becuase with the price of memory it just isn't worth not having enough...

course this doesn't apply to thiose with old motherboards that don't support more RAM...

 

The other thing to consider (and something I haven't YET) is HOW does mandrake by default use the RAM/SWAP.

(since the kernel does whatever you tell it do do)

 

My guess is it will do it very poorly.

My basis for this is whenever I look at a mandrake default setting its so generalised as to be rubbish.

 

Anyone want 10-20GB of FREE diskspace ??? simple just get rid of diskdrake when using a HUGE 60GB disk.

 

If we do the windows comparison then Mandrake is doing pretty good....

BUT I doubt it is configured to handle a gig+ well.

 

Im still trying to work out the diff's between the Mandrake-enterprise kernel AND the Mandrake vanilla.....

It isn't as simple as a recompile with 4GB RAM....that I do know.

 

Problem is the Makefiles on the kernel source ARE NOT the ones used by Mandrake.

Of this I am sure becuase the symbols are different. However what exactly they are ????

 

 

Another point. Lets say you use shared memory. Mandrake is configured without SHMEM .....

So if you want to run an app that depends on SHMEM (say Xine in XShmem mode) of course it isn't using the memory and runs like a dog.

 

So if you use apps that use SHMEM you need to reserve the memory at boot time. (along with changing the hostname this is a reboot procedure)

 

Linux in general ...

the limit is 2^32 bytes (4TB) unless you are lucky enough to be running on a 64 bit platform :D (in theory)

However the difference between LOMEM support and HIMEM support is also worth considering. In particualr, is it worth the difference of having 1GB vs 860MB bearing in mind you have to swap mem registers over to use the HIMEM anyway???

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This is a printout of my memory-usage while browsing(Firebird), listening music(xine), my mailclient (thunderbird)(more background). I use gnome. So, nothing really intensive. I have to say..I don't really have to complain. I suppose I use some swap from time to time..but what I have to see shows up quick enough. Here's a print-out of my memory at the moment:

 

:P :P total used free shared buffers cached

Mem: 126360 120376 5984 0 2996 39580

-/+ buffers/cache: 77800 48560

Swap: 306896 63340 243556

 

... I have 128 MB SDRAM...

 

I was thinking about buying some ram...but since I don't really need it .. I mostley postpone and spend my moeney on other things :). Now that I look at it..mayeb I'll make my swap-partion smaller sometime...

 

While writing this post I noticed taht spaces are compressed or something sorry about the layout.... So I used emoticons :juggle: It's teh command free on the CLI (in the cas eyou didn't know that already).

Edited by Michel
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Yeah

The kernel will try and omtimise RAM usage and SWAP usage and if you don't have it will attempt as best it can (according to how its set up) to manage with whatever you have.

 

If you have more RAM it will quite happily use it and you can force it to be more agressive too.

This applies to all levels on a linux system, from the kernel to the DM/WM. For instance in KDE you can preload a konqueror instance into memory or with startoffice you can pre-load etc. If you have the RAM its a good use of it.

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I've never actually been able to allocate more than 2GB to any specific process on a 32-bit machine - I guess thats as big as a single memory register can go. Theres a neat trick that if you actually have more ram (say the 8GB on the itanium 2 we have here) you can find that Linux assigns 512MB just to the PCI bus - strange. Oh, and don't use swap if you can possibly help it - thats why more RAM = good!!

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Qchem,

I think your right on the 2GB per process becuase it needs to swap in and out of the registers.

Im sure the amount allocated to the bus is tunable, you just need to recompile and find the damned allocation.

 

I see people using diskdrake all the time and complaining about lost disk space and that is just a case of using tunefs or creating the filesystems properly to start off with.

 

I'm on NT right now (UGGH) but I am pretty sure the PCI and AGP allocation is kernel tunable and Mandrake probably just uses a default.

 

In the case of the disk stuff the reserved root space defaults to 5% (which is just about right on a 10GB disk IMHO) so it wouldn't surprise me if the PCI stuff is also percentage... (might be worth a look?)

 

Just out of interest, does your motherboard only have a single PCI bus???

I would have expected (though I havn't had one to play with) that it would have a PCI and a PCI-X ??

 

I know if you do this on a multibus real workstation (as opposed to the x86 architecture) then the PCI allocation is tunable so I doubt its a limitaiton ofLinux per se.

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You're right, the itanium 2 we have does have both a PCI and a PCI-X bus - the 512MB is a total figure. I assumed that the amount of memory allocated was probably a kernel tuneable percentage and when I get time I might fiddle with it. In fact seeing as though we don't actually use any PCI cards I guess I could try removing it all together and hope nothing breaks.... :P

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Don't do this at home unless you REALLY don't want your PC anymore...

definately not at work if you value your job :jester:

I guess even my poor geek score left me with some geekish tendancies!!!

 

I once hacked a MOBO to bits and removed the serial and ISA support completely (This is 4-5 years ago) . I had a hacked bios and then removed everything from the kernel pertaining to ISA and serial access.

 

This whole process took quite a while to get something that would actually run and involved cutting the board and hacking the bios quite heavily.

 

In the end I got something that was pretty stable AND about 5% faster.

That might have been significant if I hadn't been able to go out and buy a new MOBO/CPU that would just have been 300% faster....

 

So total waste of time except the learning experience....

 

(My XBOX is currently unmodded becuase I don't trust myself to stop.... I intend to buy a second one and attack it with the soldering iron though)

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