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SubjectMemory problems

I'd like you to mention that Linux has some memory problems which
makes it questionable to run in some professional environmments.

On a server where memory gets fragmented and some programs are running
that request large amounts of RAM I often experience memory problems.

The most recent example is the following:

kuolema!root(ttyp2):/usr/src/boot-floppies# dd if=resc1440.bin of=/dev/fd0
dd: /dev/fd0: Device not configured

Looking at syslog tells me that the problem is found inside of Linux
memory management:

May 2 11:02:35 kuolema kernel: floppy0: Unable to allocate DMA memory

I have regularily experienced the same problem when working with
cdrecord. It wasn't able to get enough memory for its buffer and
therefore killing my writables.

Additionally I have also experienced the very same problem when
the machine had only 32M of RAM and using /dev/audio or /dev/dsp.

Since the problem also seems to be that one program doesn't get
enough free continues free memory, a simple workaround is to issue
'tail /dev/zero' and wait until it exits with 'memory exhauseted'.
After that you have enough continues free memory and your app will
work again.

As a result, I'm always issuing this command before I call cdrecord,
just to ensure that this is not a reason for killing my writables.

I know from a report about the glorious mindcraft benchmark that
Linux' memory management is tunable, but where is it documented
so that also not-experienced users are able to tune the system?

Please don't interpret this mail as general complaint. I don't have
enough experience to rework the mm subsystem (thanks god), so I'm
not complaining - I'm very happy to be able to use Linux - but I'd
like you experts know that there is a problem.

The machine kuolema runs 2.0.36 atm.



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