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SubjectRe: [PATCH 1/2] mm/page_alloc.c: leverage compiler to zero out used_mask
On Fri, Mar 27, 2020 at 10:32:45AM +0100, David Hildenbrand wrote:
>On 26.03.20 23:24, Wei Yang wrote:
>> Since we always clear used_mask before getting node order, we can
>> leverage compiler to do this instead of at run time.
>>
>> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
>> ---
>> mm/page_alloc.c | 3 +--
>> 1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 0e823bca3f2f..2144b6ceb119 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -5587,14 +5587,13 @@ static void build_zonelists(pg_data_t *pgdat)
>> {
>> static int node_order[MAX_NUMNODES];
>> int node, load, nr_nodes = 0;
>> - nodemask_t used_mask;
>> + nodemask_t used_mask = {.bits = {0}};
>> int local_node, prev_node;
>>
>> /* NUMA-aware ordering of nodes */
>> local_node = pgdat->node_id;
>> load = nr_online_nodes;
>> prev_node = local_node;
>> - nodes_clear(used_mask);
>>
>> memset(node_order, 0, sizeof(node_order));
>> while ((node = find_next_best_node(local_node, &used_mask)) >= 0) {
>>
>
>t480s: ~/git/linux default_online_type $ git grep "nodemask_t " | grep "="
>arch/x86/mm/numa.c: nodemask_t reserved_nodemask = NODE_MASK_NONE;
>arch/x86/mm/numa_emulation.c: nodemask_t physnode_mask = numa_nodes_parsed;
>arch/x86/mm/numa_emulation.c: nodemask_t physnode_mask = numa_nodes_parsed;
>arch/x86/mm/numa_emulation.c: nodemask_t physnode_mask = numa_nodes_parsed;
>drivers/acpi/numa/srat.c:static nodemask_t nodes_found_map = NODE_MASK_NONE;
>kernel/irq/affinity.c: nodemask_t nodemsk = NODE_MASK_NONE;
>kernel/sched/fair.c: nodemask_t max_group = NODE_MASK_NONE;
>mm/memory_hotplug.c: nodemask_t nmask = node_states[N_MEMORY];
>mm/mempolicy.c: nodemask_t mems = cpuset_mems_allowed(current);
>mm/mempolicy.c: nodemask_t nodes = NODE_MASK_NONE;
>mm/oom_kill.c: const nodemask_t *mask = oc->nodemask;
>mm/page_alloc.c:nodemask_t node_states[NR_NODE_STATES] __read_mostly = {
>mm/page_alloc.c: nodemask_t saved_node_state = node_states[N_MEMORY];
>
>Should this be NODE_MASK_NONE?

Thanks, this is gcc extension. Learn something new.

I would update this in v2.

>
>--
>Thanks,
>
>David / dhildenb

--
Wei Yang
Help you, Help me

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