Date: Mon, 22 Jan 2001 12:24:30 -0800 From: Mike Smith <msmith@freebsd.org> To: Robert Lipe <robertlipe@usa.net> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: contigmalloc, M_WAITOK, & leaks. Message-ID: <200101222024.f0MKOU001092@mass.dis.org> In-Reply-To: Your message of "Mon, 22 Jan 2001 11:06:42 CST." <20010122110642.B10504@rjlhome.sco.com>
next in thread | previous in thread | raw e-mail | index | archive | help
> 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.
No, contigmalloc will return NULL if physical memory space is fragmented
to the point where it can't honour your request.
You should avoid calling contigmalloc at any time other than when setting
up your driver; there is no support in the kernel for defragmenting
physical address space, so over time you'll run into the problem you're
seeing.
Allocate your space up front, and then leave it alone. Also, you should
probably be using bus_dmamem_alloc() since the only real use for
contiguous memory is for DMA purposes, and you'll be better served by
allocating DMA'able buffers matching your device's characteristics than
by assuming that you can DMA to/from all physical memory.
--
... every activity meets with opposition, everyone who acts has his
rivals and unfortunately opponents also. But not because people want
to be opponents, rather because the tasks and relationships force
people to take different points of view. [Dr. Fritz Todt]
V I C T O R Y N O T V E N G E A N C E
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-hackers" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200101222024.f0MKOU001092>