Date: Thu, 24 Dec 1998 03:08:18 -0500 (EST) From: "John S. Dyson" <dyson@iquest.net> To: dillon@apollo.backplane.com (Matthew Dillon) Cc: hackers@FreeBSD.ORG Subject: Re: M_KERNEL in sys/malloc.h ??? Message-ID: <199812240808.DAA46738@y.dyson.net> In-Reply-To: <199812230019.QAA08154@apollo.backplane.com> from Matthew Dillon at "Dec 22, 98 04:19:43 pm"
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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. -- John | Never try to teach a pig to sing, dyson@iquest.net | it makes one look stupid jdyson@nc.com | and it irritates the pig. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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