hwloc.h+bind.1in: add a note about hwloc bind policy != linux bind

Refs #601.

Signed-off-by: Brice Goglin <[email protected]>

Author: bgoglin

include/hwloc.h

@@ -1507,6 +1507,12 @@ typedef enum {
   HWLOC_MEMBIND_FIRSTTOUCH =	1,
 
   /** \brief Allocate memory on the specified nodes.
+   *
+   * The actual behavior may slightly vary between operating systems,
+   * especially when (some of) the requested nodes are full.
+   * On Linux, by default, the MPOL_PREFERRED_MANY (or MPOL_PREFERRED) policy
+   * is used. However, if the hwloc strict flag is also given, the Linux
+   * MPOL_BIND policy is rather used.
    * \hideinitializer */
   HWLOC_MEMBIND_BIND =		2,
 

utils/hwloc/hwloc-bind.1in

@@ -100,13 +100,22 @@ the default policy is bind.
 .TP
 \fB\-\-mempolicy\fR <policy>
 Change the memory binding policy.
-The available policies are default, firsttouch, bind, interleave
-and nexttouch.
+
 This option is only meaningful when an actual binding is also given
 with \fB\-\-membind\fR.
 If \fB\-\-membind\fR is given without \fB\-\-mempolicy\fR,
 the default policy is bind.
 
+The available policies are \fBdefault\fR, \fBfirsttouch\fR,
+\fBbind\fR, \fBinterleave\fR and \fBnexttouch\fR.
+See hwloc.h for details about these policies.
+
+Note that hwloc's memory binding policies may be slightly different
+from operating system policies.
+For instance, the hwloc \fBbind\fR policy uses Linux \fIMPOL_PREFERRED_MANY\fR
+(or \fIMPOL_PREFERRED\fR) by default, but it switches to Linux \fIMPOL_BIND\fR
+if the hwloc strict option or flag is also given.
+
 .TP
 \fB\-\-get\fR
 Report the current bindings.