On Thu, Nov 15, 2012 at 11:32:18AM -0600, Alan Cox wrote: > On 11/13/2012 05:54, Konstantin Belousov wrote: > > On Mon, Nov 12, 2012 at 05:10:01PM -0600, Alan Cox wrote: > >> On 11/12/2012 3:48 PM, Konstantin Belousov wrote: > >>> On Mon, Nov 12, 2012 at 01:28:02PM -0800, Sushanth Rai wrote: > >>>> This patch still doesn't address the issue of M_NOWAIT calls driving > >>>> the memory the all the way down to 2 pages, right ? It would be nice to > >>>> have M_NOWAIT just do non-sleep version of M_WAITOK and M_USE_RESERVE > >>>> flag to dig deep. > >>> This is out of scope of the change. But it is required for any further > >>> adjustements. > >> I would suggest a somewhat different response: > >> > >> The patch does make M_NOWAIT into a "non-sleep version of M_WAITOK" and > >> does reintroduce M_USE_RESERVE as a way to specify "dig deep". > >> > >> Currently, both M_NOWAIT and M_WAITOK can drive the cache/free memory > >> down to two pages. The effect of the patch is to stop M_NOWAIT at two > >> pages rather than allowing it to continue to zero pages. > >> > >> When you say, "This is out of scope ...", I believe that you are > >> referring to changing two pages into something larger. I agree that > >> this is out of scope for the current change. > > I referred exactly to the difference between M_USE_RESERVE set or not. > > IMO this is what was asked by the question author. So yes, my mean of > > the 'out of scope' is about tweaking the 'two pages reserve' in some > > way. > > Since M_USE_RESERVE is no longer deprecated in HEAD, here is my proposed > man page update to malloc(9): > > Index: share/man/man9/malloc.9 > =================================================================== > --- share/man/man9/malloc.9 (revision 243091) > +++ share/man/man9/malloc.9 (working copy) > @@ -29,7 +29,7 @@ > .\" $NetBSD: malloc.9,v 1.3 1996/11/11 00:05:11 lukem Exp $ > .\" $FreeBSD$ > .\" > -.Dd January 28, 2012 > +.Dd November 15, 2012 > .Dt MALLOC 9 > .Os > .Sh NAME > @@ -153,13 +153,12 @@ if > .Dv M_WAITOK > is specified. > .It Dv M_USE_RESERVE > -Indicates that the system can dig into its reserve in order to obtain the > -requested memory. > -This option used to be called > -.Dv M_KERNEL > -but has been renamed to something more obvious. > -This option has been deprecated and is slowly being removed from the > kernel, > -and so should not be used with any new programming. > +Indicates that the system can use its reserve of memory to satisfy the > +request. > +This option should only be used in combination with > +.Dv M_NOWAIT > +when an allocation failure cannot be tolerated by the caller without > +catastrophic effects on the system. > .El > .Pp > Exactly one of either
The text looks fine. Shouldn't the requirement for M_USE_RESERVE be also
expressed in KASSERT, like this:
diff --git a/sys/vm/vm_page.h b/sys/vm/vm_page.h
index d9e4692..f8a4f70 100644
--- a/sys/vm/vm_page.h
+++ b/sys/vm/vm_page.h
@@ -353,6 +351,9 @@ malloc2vm_flags(int malloc_flags)
{
int pflags;
+ KASSERT((malloc_flags & M_USE_RESERVE) == 0 ||
+ (malloc_flags & M_NOWAIT) != 0,
+ ("M_USE_RESERVE requires M_NOWAIT"));
pflags = (malloc_flags & M_USE_RESERVE) != 0 ? VM_ALLOC_INTERRUPT :
VM_ALLOC_SYSTEM;
if ((malloc_flags & M_ZERO) != 0)
I understand that this could be added to places of the allocator's entries,
but I think that the page allocations are fine too.
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