Re: [PATCH] Fix test/prefered v2

[Cliff Wickman <cpw@sgi.com>]

Hi Andi,

> Date: Sat, 10 Jan 2009 07:18:09 +0100
> From: Andi Kleen <andi@firstfloor.org>
> To: Andi Kleen <andi@firstfloor.org>
> Cc: cpw@sgi.com, linux-numa@vger.kernel.org
> Subject: [PATCH] Fix test/prefered v2
> 
> Fix test/prefered v2
>  
> Couple of bugs here:
>  
> - First the kernel errors out of the nodemask is < MAXNUMNODES,
> so have to discover that at runtime. There's no function
> in libnuma for this (perhaps there should be one?), so i
> wrote one here.

There is numa_num_possible_nodes(). It determines the size of
the kernel nodemask_t (MAX_NUMNODES) by counting the size of Mems_allowed:
in /proc/self/status. (And if that is not available, falls back to a
procedure very similar to your max_numnode().)
The patch, but using numa_num_possible_nodes() is below.
It returns the same results, in my tests.

Is there some subtle difference between numa_num_possible_nodes() and
your function that I'm missing?

-Cliff

> - The loop set the node in the wrong mask, breaking the test
> 
> v2: Correct max_numnode detection
> 
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> 
> --- numactl-2.0.2/test/prefered.c	2008-08-05 16:36:58.000000000 +0200
> +++ numactl-2.0.2-hack/test/prefered.c	2009-01-10 07:00:16.000000000 +0100
> @@ -6,20 +6,38 @@
>  #include <assert.h>
>  #include <unistd.h>
>  #include <stdlib.h>
> +#include <errno.h>
>  
>  #define err(x) perror(x),exit(1)
>  
> +/* Discover MAXNUMNODE of the kernel */
> +int max_numnode(void)
> +{	
> +	int v;
> +	unsigned size = 64;
> +	struct bitmask *mask = numa_bitmask_alloc(size);
> +	while (get_mempolicy(NULL, mask->maskp, mask->size, &v, MPOL_F_ADDR) < 0 &&
> +			errno == EINVAL) {
> +		numa_bitmask_free(mask);
> +		size <<= 1;
> +		mask = numa_bitmask_alloc(size);
> +	}
> +	numa_bitmask_free(mask);
> +	return size;
> +}
> +
>  int main(void)
>  {
>  	int max = numa_max_node();
> +	int maxmask = max_numnode();
>  	struct bitmask *nodes, *mask;
>  	int pagesize = getpagesize();
>  	int i;
>  	int pol;
>  	int node;
>  	int err = 0;
> -	nodes = numa_bitmask_alloc(max+1);
> -	mask = numa_bitmask_alloc(max+1);
> +	nodes = numa_bitmask_alloc(maxmask);
> +	mask = numa_bitmask_alloc(maxmask);
>  
>  	for (i = max; i >= 0; --i) { 
>  		char *mem = mmap(NULL, pagesize*(max+1), PROT_READ|PROT_WRITE, 
> @@ -33,8 +51,8 @@
>  
>  		numa_bitmask_clearall(nodes);
>  		numa_bitmask_clearall(mask);
> -		numa_bitmask_setbit(mask, i);
> +		numa_bitmask_setbit(nodes, i);
>  
>  		if (mbind(adr,  pagesize, MPOL_PREFERRED, nodes->maskp,
>  							nodes->size, 0) < 0)
>  			err("mbind");

---
 test/prefered.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

Index: numactl-dev/test/prefered.c
===================================================================
--- numactl-dev.orig/test/prefered.c
+++ numactl-dev/test/prefered.c
@@ -6,20 +6,22 @@
 #include <assert.h>
 #include <unistd.h>
 #include <stdlib.h>
+#include <errno.h>
 
 #define err(x) perror(x),exit(1)
 
 int main(void)
 {
 	int max = numa_max_node();
+	int maxmask = numa_num_possible_nodes();
 	struct bitmask *nodes, *mask;
 	int pagesize = getpagesize();
 	int i;
 	int pol;
 	int node;
 	int err = 0;
-	nodes = numa_bitmask_alloc(max+1);
-	mask = numa_bitmask_alloc(max+1);
+	nodes = numa_bitmask_alloc(maxmask);
+	mask = numa_bitmask_alloc(maxmask);
 
 	for (i = max; i >= 0; --i) { 
 		char *mem = mmap(NULL, pagesize*(max+1), PROT_READ|PROT_WRITE, 
@@ -33,7 +35,7 @@ int main(void)
 
 		numa_bitmask_clearall(nodes);
 		numa_bitmask_clearall(mask);
-		numa_bitmask_setbit(mask, i);
+		numa_bitmask_setbit(nodes, i);
 
 		if (mbind(adr,  pagesize, MPOL_PREFERRED, nodes->maskp,
 							nodes->size, 0) < 0)