Hi, Matthew,
Matthew Wilcox <willy@xxxxxxxxxxxxx> writes:
> On Tue, Jun 25, 2024 at 02:26:05PM +0100, Tvrtko Ursulin wrote:
>> /*
>> - * Currently, the only defined flags are mutually exclusive
>> + * The below two flags are mutually exclusive:
>> */
>> if (flags & MPOL_F_STATIC_NODES)
>> p += snprintf(p, buffer + maxlen - p, "static");
>> else if (flags & MPOL_F_RELATIVE_NODES)
>> p += snprintf(p, buffer + maxlen - p, "relative");
>> +
>> + if (flags & MPOL_F_NUMA_BALANCING)
>> + p += snprintf(p, buffer + maxlen - p, "balancing");
>> }
>
> So if MPOL_F_STATIC_NODES and MPOL_F_NUMA_BALANCING are set, then we
> get a string "staticbalancing"? Is that intended?
>
> Or are these three all mutually exclusive and that should have been
> as "else if"?
Yes, this is an issue!
Dig the git history, in commit 2291990ab36b ("mempolicy: clean-up
mpol-to-str() mempolicy formatting"), the support for multiple flags are
removed. I think that we need to restore it.
Done some basic testing. It was found that when MPOL_F_NUMA_BALANCING
is set, /proc/PID/numa_maps always display "default". That is wrong.
This make me think that this patch has never been tested!
The "default" displaying is introduced in commit 8790c71a18e5
("mm/mempolicy.c: fix mempolicy printing in numa_maps"). We need to fix
it firstly for MPOL_F_NUMA_BALANCING with more accurate filtering. The
fix needs to be backported to -stable kernel.
--
Best Regards,
Huang, Ying
