On Wed, Jun 26, 2013 at 08:53:36PM -0400, Andrew J. Schorr wrote:
> I tried calling set_mempolicy directly for this trivial case, but I get
> EINVAL when I try:
>
> {
> unsigned long mask = 1;
> set_mempolicy(MPOL_BIND, &mask, 1);
> }
>
> Increasing the 3rd arg from 1 to 2 seems to solve the problem, but I cannot
> understand why from "man 2 set_mempolicy".
In linux-3.6/mm/mempolicy.c:get_nodes(), maxnode is decremented immediately. I
cannot see from the man page why that is done, but it seems to explain the
problem I found. I guess this explains why libnuma.c:setpol adds 1 to the
bitmask size. But I still cannot see where this odd behavior is documented in
the man page. If anybody can enlighten me, I'd appreciate it.
Perhaps this is why it is not recommended to use this API directly. :-)
Regards,
Andy
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