Re: Module loading (2.0.24) fails with "Unable to allocate DMA memory"

Jean Francois Martinez (
Mon, 11 Nov 1996 00:34:18 +0100

From: (Alan Cox)
Date: Sun, 10 Nov 1996 14:28:37 +0000 (GMT)
Content-Type: text

> start. IMO the matter is serious. It makes the Linux kernel
> unreliable. Imagine a cron task in a sever failing because the module
> needed canot get DMA memory. That's not the kind of things who
> must perdure in Linux now it is gaining public exposure.

Its more a nuisance than anything else. The only thing it gets me with
is the floppy module and I just load that with dma disabled. Not ideal. All
it effects is ISA bus DMA allocations. We don't need large contiguous blocks
for many other things currently (modules are loaded into a space via vmalloc
which uses page table entries to stick the pages together into a big block).

Modules have other problems too - they run slightly slower for example.


In preceeding versions of 2.0 I had the same problem with ppp and
cdrom, rare and not reproducible. Another person menions the problem
with ftape. I don't know if you use modules intensively. I tend to
modularize everything possible. Because they are vital to linux's use
expansion I keep them under watch.

If you ask a person who has never used UNIX to recompile his kernel
just ten minutes after having ended installation then he will not come
to LINUX. Linux will be used only by hackers and sooner or later its
use will no longer increase (no more hackers). With modules we can
provide users with a nearly optimal kernel so he is not compelled to
recompile (he can but is not mandatory). And we will have a hope
(with adequate utilities) to attract more people to Linux. Unreliable
modules can be a minor nuisance to you but I think it is not so minor
for Linux.


Jean Francois Martinez

-What is the operating system used by Bill Gates? -Linux of course. Do you think stupid people become millionnaire?