On Fri, Dec 2, 2022 at 12:00 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Fri, 2 Dec 2022 22:16:30 +0800 tzm <tcm1030@xxxxxxx> wrote:
>
> > It will be failed to disable numa balancing policy permanently by passing
> > <numa_balancing=disable> to boot cmdline parameters.
> > The numabalancing_override variable is int and 1 for enable -1 for disable.
> > So, !enumabalancing_override will always be true, which cause this bug.
>
> That's really old code!
>
> > --- a/mm/mempolicy.c
> > +++ b/mm/mempolicy.c
> > @@ -2865,7 +2865,7 @@ static void __init check_numabalancing_enable(void)
> > if (numabalancing_override)
> > set_numabalancing_state(numabalancing_override == 1);
> >
> > - if (num_online_nodes() > 1 && !numabalancing_override) {
> > + if (num_online_nodes() > 1 && (numabalancing_override == 1)) {
> > pr_info("%s automatic NUMA balancing. Configure with numa_balancing= or the kernel.numa_balancing sysctl\n",
> > numabalancing_default ? "Enabling" : "Disabling");
> > set_numabalancing_state(numabalancing_default);
>
> Looks right to me. Mel?
>
Maybe I'm missing something, but it looks wrong to me?
numabalancing_override is default initialized to 0, I think,
indicating that no override exists.
numabalancing_override == 1 indicates it has been overridden to true.
numabalancing_override == -1 indicates that it has been overridden to false.
The above code reads to me:
if (override_exists)
set_numabalancing_state(override_value)
if (num_online_nodes() > ! && !override_exists)
set_numabalancing_state(numabalancing_default)
A more clear fix for readability would be an early return between
these 2 if statements I think.
> After eight years, I wonder if we actually need this.
>
