* Robert Lipe <[EMAIL PROTECTED]> [010122 09:04] wrote:
> Hi, Gang.
>
> I know that anytime a message starts with a subject like this, the
> first reaction is to think that I've hosed the heap or am not freeing
> something. While it's possible, I really don't think I have. (I also
> know that everyone thinks that. :-)
>
> I'm on FreeBSD 4.1.1. I've not seen any flagrantly smoking guns since
> then in vm_page.c, although version 1.154 might be...
>
> I'm calling contigmalloc() with M_WAITOK. For every contigmalloc, I
> have a corresponding contigfree(). But after a few thousand cycles,
> contigmalloc() starts returning NULL. It self-destructs in about 3
> minutes. I see the same behaviour with M_NOWAIT. As an aside, WAITOK's
> should never return NULL, right? They should be put to sleep and
> awakened when the resource is available.
Making heavy use of contigmalloc is a bad idea, if you really need
this contig allocations then allocate a fair number of them early
and keep using them. Memory get's fragmented, there's not much
you can do about it. I doubt that contigmalloc respects the WAITOK
flag, there's a good chance that kernel memory has become so
fragmented that your chances of successfully completing the
contigmalloc are near zero, it's much better to return a temporary
resource failure than block a kernel thread forever.
This issue has come up before, and most everyone was able to either
use a workaround (calling VTOPHYS? on each page) or pre-allocating
the contig space and reuseing it instead of allocating and freeing
it over and over.
best of luck,
-Alfred
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