Re: [PATCH] mm/page_alloc: Clean up check_for_memory

On 8/31/18 8:24 AM, Oscar Salvador wrote:

On Thu, Aug 30, 2018 at 01:55:29AM +0000, Pasha Tatashin wrote:

quoted

I would re-write the above function like this:
static void check_for_memory(pg_data_t *pgdat, int nid)
{
        enum zone_type zone_type;

        for (zone_type = 0; zone_type < ZONE_MOVABLE; zone_type++) {
                if (populated_zone(&pgdat->node_zones[zone_type])) { 
                        node_set_state(nid, zone_type <= ZONE_NORMAL ?
                                       N_NORMAL_MEMORY: N_HIGH_MEMORY);
                        break;
                }
        }
}

Hi Pavel,

the above would not work fine.
You set either N_NORMAL_MEMORY or N_HIGH_MEMORY, but a node can have both
types of memory at the same time (on CONFIG_HIGHMEM systems).

N_HIGH_MEMORY stands for regular or high memory
while N_NORMAL_MEMORY stands only for regular memory,
that is why we set it only in case the zone is <= ZONE_NORMAL.

Hi Oscar,

Are you saying the code that is in mainline is broken? Because we set
node_set_state(nid, N_NORMAL_MEMORY); even on node with N_HIGH_MEMORY:

6826			if (N_NORMAL_MEMORY != N_HIGH_MEMORY &&
6827			    zone_type <= ZONE_NORMAL)
6828				node_set_state(nid, N_NORMAL_MEMORY);

Thank you,
Pavel