On 9/17/2020 2:28 AM, Michal Hocko wrote:
On Wed 16-09-20 23:39:39, Vijay Balakrishna wrote:
set_recommended_min_free_kbytes need to honor min_free_kbytes set by the
user. Post start-of-day THP enable or memory hotplug operations can
lose user specified min_free_kbytes, in particular when it is higher than
calculated recommended value.
I was about to recommend a more detailed explanation when I have
realized that this patch is not really needed after all. Unless I am
missing something.
init_per_zone_wmark_min ignores the newly calculated min_free_kbytes if
it is lower than user_min_free_kbytes. So calculated min_free_kbytes >=
user_min_free_kbytes.
Except for value clamping when the value is reduced and this likely
needs fixing. But set_recommended_min_free_kbytes should be fine.
IIUC, after start-of-day if a user performs
- THP disable
- modifies min_free_bytes
- THP enable
above sequence currently wouldn't result in calling init_per_zone_wmark_min.
Thanks,
Vijay
