5Mb missing...

5Mb missing...

[Alex Baretta]

Mike Galbraith wrote:
> 
> If crashes are routine on this machine, I'd recommend that you take
> a serious look at your ram. (or if you're overclocking, don't)

Crashes were routine, and I was not overclocking, so I took Mike's
advice and bought a new 256MB DIMM. The computer hasn't crashed
once since I installed it. Now, though, I have a curious though
fairly irrelevant problem. My kernel apparently sees less RAM than
I have.


[alex@localhost /home]$ free -m
             total       used       free     shared    buffers    
cached
Mem:           251        209         42         60        
61         92
-/+ buffers/cache:         55        196


I strongly doubt this can be a bug in the kernel. Could anyone
explain to me why this might happen?

Alex

Re: 5Mb missing...

[Mike Dresser]

Alex Baretta wrote:

> [alex@localhost /home]$ free -m
>              total       used       free     shared    buffers
> cached
> Mem:           251        209         42         60
> 61         92
>
> I strongly doubt this can be a bug in the kernel. Could anyone
> explain to me why this might happen?

grep Memory /var/log/kern.log

You've got your kernel itself loading into ram, reserved memory, etc.

I've got 48 meg in this test box of mine, and a free -m shows 46, a free shows
47356.  Divided by 1024, gives 46, when rounded off.  So yes, free -m is
correct.  That 251 meg is what's available to use, after your kernel loads,
etc.

mike

Re: 5Mb missing...

[Mordechai Ovits]

On Wed, Mar 14, 2001 at 03:06:09PM +0100, Alex Baretta wrote:
> Mike Galbraith wrote:
> > 
> > If crashes are routine on this machine, I'd recommend that you take
> > a serious look at your ram. (or if you're overclocking, don't)
> 
> Crashes were routine, and I was not overclocking, so I took Mike's
> advice and bought a new 256MB DIMM. The computer hasn't crashed
> once since I installed it. Now, though, I have a curious though
> fairly irrelevant problem. My kernel apparently sees less RAM than
> I have.
> 
> 
> [alex@localhost /home]$ free -m
>              total       used       free     shared    buffers    
> cached
> Mem:           251        209         42         60        
> 61         92
> -/+ buffers/cache:         55        196
> 
> 
> I strongly doubt this can be a bug in the kernel. Could anyone
> explain to me why this might happen?

when you boot, your bios decides how much ram is "really" available,
usually for  good reasons.  If the bios knows that its power management
routines need a few meg off the top it'll report a few less meg to the OS
that is to be booted.  You can tell linux to ignore the bios with the kernel
parameter mem=256, but I highly recommend *against* it in this case.  Look
into it.

Mordy
 
> Alex
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Re: 5Mb missing...

[Jonathan Morton]

>> If crashes are routine on this machine, I'd recommend that you take
>> a serious look at your ram. (or if you're overclocking, don't)
>
>Crashes were routine, and I was not overclocking, so I took Mike's
>advice and bought a new 256MB DIMM. The computer hasn't crashed
>once since I installed it. Now, though, I have a curious though
>fairly irrelevant problem. My kernel apparently sees less RAM than
>I have.

The kernel itself takes up some RAM, which is simply subtracted from the
"total memory available" field in the memory summaries available to
user-mode processes.  This is perfectly normal.

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uni-mail: j.d.morton@lancaster.ac.uk

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Re: 5Mb missing...

[Martin Dalecki]

Jonathan Morton wrote:
> 
> >> If crashes are routine on this machine, I'd recommend that you take
> >> a serious look at your ram. (or if you're overclocking, don't)
> >
> >Crashes were routine, and I was not overclocking, so I took Mike's
> >advice and bought a new 256MB DIMM. The computer hasn't crashed
> >once since I installed it. Now, though, I have a curious though
> >fairly irrelevant problem. My kernel apparently sees less RAM than
> >I have.
> 
> The kernel itself takes up some RAM, which is simply subtracted from the
> "total memory available" field in the memory summaries available to
> user-mode processes.  This is perfectly normal.

The kernel reserves 4m for hilself. The off by one error is a rounding
bug.

Re: 5Mb missing...

[Alex Baretta]

Martin Dalecki wrote:
> 
> Jonathan Morton wrote:
> >
> > The kernel itself takes up some RAM, which is simply subtracted from the
> > "total memory available" field in the memory summaries available to
> > user-mode processes.  This is perfectly normal.
> 
> The kernel reserves 4m for hilself. The off by one error is a rounding
> bug.

Sounds pretty reasonable. I have actually tested the memory card
with memtest, just to make sure that it was all there and working
properly, and the test succeeded, so it must really be the kernel
eating away a few megs.

Alex