Date: Thu, 24 Dec 1998 11:59:46 -0800 (PST) From: Julian Elischer <julian@whistle.com> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: "John S. Dyson" <dyson@iquest.net>, hackers@FreeBSD.ORG Subject: Re: M_KERNEL in sys/malloc.h ??? Message-ID: <Pine.BSF.3.95.981224115800.12901C-100000@current1.whistle.com> In-Reply-To: <199812241721.JAA27982@apollo.backplane.com>
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I would rename it to M_RESERVED or something that indicates
that this is a request that is allowed dip into the emergency reserves
to satisfy the request.
On Thu, 24 Dec 1998, Matthew Dillon wrote:
>
> :Matthew Dillon said:
> :> Does anyone know what M_KERNEL is sys/malloc.h is supposed to do? It
> :> is used in precisely two places in the code as far as I can tell:
> :>
> :> vm/default_pager.c: if (swap_pager_swp_alloc(object, M_KERNEL) != 0) {
> :> vm/default_pager.c: if (swap_pager_swp_alloc(object, M_KERNEL) != 0) {
> :> vm/swap_pager.c: spc->spc_bp = malloc(sizeof(*bp), M_TEMP, M_KERNEL);
> :>
> :> But kern/kern_malloc.c doesn't appear to really use it. On the otherhand
> :> I do see lots of absolute comparison of the malloc 'flags' to M_WAITOK
> :> (0) or M_NOWAIT which the use of M_KERNEL would interfere with. I can't
> :> tell if the side effects are something that are expected, or if the
> :> side effects are a bug.
> :>
> :> Anybody know?
> :>
> :As I remember, M_KERNEL means that it really needs memory. waiting
> :for memory is bad, and dip deeply into the page reserves. Normally, the
> :malloc (in vm_kern) code will only dip into the interrupt accessible
> :free pages. The M_KERNEL allows it to dip into all of the pages.
>
> Ok, I'll document it then and make sure it operates the same with my
> cleanups.
>
> -Matt
>
> :John | Never try to teach a pig to sing,
> :dyson@iquest.net | it makes one look stupid
>
> Matthew Dillon Engineering, HiWay Technologies, Inc. & BEST Internet
> Communications & God knows what else.
> <dillon@backplane.com> (Please include original email in any response)
>
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