Gregory Price <gregory.price@xxxxxxxxxxxx> writes:
> On Tue, Jan 23, 2024 at 04:35:19PM +0800, Huang, Ying wrote:
>> Gregory Price <gregory.price@xxxxxxxxxxxx> writes:
>>
>> > On Mon, Jan 22, 2024 at 11:54:34PM -0500, Gregory Price wrote:
>> >> >
>> >> > Can the above code be simplified as something like below?
>> >> >
>> >> > resume_node = prev_node;
>> > --- resume_weight = 0;
>> > +++ resume_weight = weights[node];
>> >> > for (...) {
>> >> > ...
>> >> > }
>> >> >
>> >>
>> >> I'll take another look at it, but this logic is annoying because of the
>> >> corner case: me->il_prev can be NUMA_NO_NODE or an actual numa node.
>> >>
>> >
>> > After a quick look, as long as no one objects to (me->il_prev) remaining
>> > NUMA_NO_NODE
>>
>> MAX_NUMNODES-1 ?
>>
>
> When setting a new policy, the il_prev gets set to NUMA_NO_NODE. It's
IIUC, it is set to MAX_NUMNODES-1 as below,
@@ -846,7 +858,8 @@ static long do_set_mempolicy(unsigned short mode, unsigned short flags,
old = current->mempolicy;
current->mempolicy = new;
- if (new && new->mode == MPOL_INTERLEAVE)
+ if (new && (new->mode == MPOL_INTERLEAVE ||
+ new->mode == MPOL_WEIGHTED_INTERLEAVE))
current->il_prev = MAX_NUMNODES-1;
task_unlock(current);
mpol_put(old);
I don't think we need to change this.
> not harmful and is just (-1), which is functionally the same as
> (MAX_NUMNODES-1) for the purpose of iterating the nodemask with
> next_node_in(). So it's fine to set (resume_node = me->il_prev)
> as discussed.
>
> I have a cleaned up function I'll push when i fix up a few other spots.
>
>> > while having a weight assigned to pol->wil.cur_weight,
>>
>> I think that it is OK.
>>
>> And, IIUC, pol->wil.cur_weight can be 0, as in
>> weighted_interleave_nodes(), if it's 0, it will be assigned to default
>> weight for the node.
>>
>
> cur_weight is different than the global weights. cur_weight tells us
> how many pages are remaining to allocate for the current node.
>
> (cur_weight = 0) can happen in two scenarios:
> - initial setting of mempolicy (NUMA_NO_NODE w/ cur_weight=0)
> - weighted_interleave_nodes decrements it down to 0
>
> Now that i'm looking at it - the second condition should not exist, and
> we can eliminate it. The logic in weighted_interleave_nodes is actually
> annoyingly unclear at the moment, so I'm going to re-factor it a bit to
> be more explicit.
I am OK with either way. Just a reminder, the first condition may be
true in alloc_pages_bulk_array_weighted_interleave() and perhaps some
other places.
--
Best Regards,
Huang, Ying
