On Wed, 2009-08-26 at 11:11 +0100, Mel Gorman wrote:
> On Tue, Aug 25, 2009 at 04:49:29PM -0400, Lee Schermerhorn wrote:
> > > >
> > > > +static nodemask_t *nodes_allowed_from_node(int nid)
> > > > +{
> > >
> > > This name is a bit weird. It's creating a nodemask with just a single
> > > node allowed.
> > >
> > > Is there something wrong with using the existing function
> > > nodemask_of_node()? If stack is the problem, prehaps there is some macro
> > > magic that would allow a nodemask to be either declared on the stack or
> > > kmalloc'd.
> >
> > Yeah. nodemask_of_node() creates an on-stack mask, invisibly, in a
> > block nested inside the context where it's invoked. I would be
> > declaring the nodemask in the compound else clause and don't want to
> > access it [via the nodes_allowed pointer] from outside of there.
> >
>
> So, the existance of the mask on the stack is the problem. I can
> understand that, they are potentially quite large.
>
> Would it be possible to add a helper along side it like
> init_nodemask_of_node() that does the same work as nodemask_of_node()
> but takes a nodemask parameter? nodemask_of_node() would reuse the
> init_nodemask_of_node() except it declares the nodemask on the stack.
>
<snip>
Here's the patch that introduces the helper function that I propose.
I'll send an update of the subject patch that uses this macro and, I
think, addresses your other issues via a separate message. This patch
applies just before the "register per node attributes" patch. Once we
can agree on these [or subsequent] changes, I'll repost the entire
updated series.
Lee
---
PATCH 4/6 - hugetlb: introduce alloc_nodemask_of_node()
Against: 2.6.31-rc6-mmotm-090820-1918
Introduce nodemask macro to allocate a nodemask and
initialize it to contain a single node, using existing
nodemask_of_node() macro. Coded as a macro to avoid header
dependency hell.
This will be used to construct the huge pages "nodes_allowed"
nodemask for a single node when a persistent huge page
pool page count is modified via a per node sysfs attribute.
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@xxxxxx>
include/linux/nodemask.h | 10 ++++++++++
1 file changed, 10 insertions(+)
Index: linux-2.6.31-rc6-mmotm-090820-1918/include/linux/nodemask.h
===================================================================
--- linux-2.6.31-rc6-mmotm-090820-1918.orig/include/linux/nodemask.h 2009-08-24 10:16:56.000000000 -0400
+++ linux-2.6.31-rc6-mmotm-090820-1918/include/linux/nodemask.h 2009-08-26 12:38:31.000000000 -0400
@@ -257,6 +257,16 @@ static inline int __next_node(int n, con
m; \
})
+#define alloc_nodemask_of_node(node) \
+({ \
+ typeof(_unused_nodemask_arg_) *nmp; \
+ nmp = kmalloc(sizeof(*nmp), GFP_KERNEL); \
+ if (nmp) \
+ *nmp = nodemask_of_node(node); \
+ nmp; \
+})
+
+
#define first_unset_node(mask) __first_unset_node(&(mask))
static inline int __first_unset_node(const nodemask_t *maskp)
{
--
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