On 2021/5/28 7:47, Baoquan He wrote:
> On 05/27/21 at 08:57pm, Liu Shixin wrote:
>> The commit f63661566fad (mm/page_alloc.c: clear out zone->lowmem_reserve[]
>> if the zone is empty) clear out zone->lowmem_reserve[] if zone is empty.
>> But when zone is not empty and sysctl_lowmem_reserve_ratio[i] is set to zero,
>> zone_managed_pages(zone) is not counted in the managed_pages either. This is
>> inconsistent with the description of lowmen_reserve, so fix it.
> Right, this is a good catch. Thanks for the fixing.
>
> Is it worth adding words in Documentation/admin-guide/sysctl/vm.rst
> to notice this?
>
> Reviewed-by: Baoquan He <bhe@xxxxxxxxxx>
>
> Thanks
> Baoquan
With this patch, It's consistent with the calculation description of zone[i]'s protection[j].
This is implicit in the description so I don't think it's necessary to notice this.
>> Fixes: f63661566fad ("mm/page_alloc.c: clear out zone->lowmem_reserve[] if the zone is empty")
>> Reported-by: yangerkun <yangerkun@xxxxxxxxxx>
>> Signed-off-by: Liu Shixin <liushixin2@xxxxxxxxxx>
>> ---
>> mm/page_alloc.c | 12 ++++++------
>> 1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index aaa1655cf682..49a2efce5a84 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -8061,14 +8061,14 @@ static void setup_per_zone_lowmem_reserve(void)
>> unsigned long managed_pages = 0;
>>
>> for (j = i + 1; j < MAX_NR_ZONES; j++) {
>> - if (clear) {
>> - zone->lowmem_reserve[j] = 0;
>> - } else {
>> - struct zone *upper_zone = &pgdat->node_zones[j];
>> + struct zone *upper_zone = &pgdat->node_zones[j];
>> +
>> + managed_pages += zone_managed_pages(upper_zone);
>>
>> - managed_pages += zone_managed_pages(upper_zone);
>> + if (clear)
>> + zone->lowmem_reserve[j] = 0;
>> + else
>> zone->lowmem_reserve[j] = managed_pages / ratio;
>> - }
>> }
>> }
>> }
>> --
>> 2.18.0.huawei.25
>>
>>
> .
>
