On 9/30/2020 11:20 AM, Mike Kravetz wrote:
On 9/29/20 9:49 AM, Vijay Balakrishna wrote:When memory is hotplug added or removed the min_free_kbytes should be recalculated based on what is expected by khugepaged. Currently after hotplug, min_free_kbytes will be set to a lower default and higher default set when THP enabled is lost. This change restores min_free_kbytes as expected for THP consumers. Fixes: f000565adb77 ("thp: set recommended min free kbytes") Signed-off-by: Vijay Balakrishna <vijayb@xxxxxxxxxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Reviewed-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx>Sorry for jumping in so late. Should we use this as an opportunity to also fix up the messages logged when (re)calculating mfk? They are wrong and could be quite confusing.
Sure. Please share your thoughts regarding appropriate message. Here is what I'm thinking
pr_warn("min_free_kbytes is not updated to %d because current value %d is preferred\n", new_min_free_kbytes, min_free_kbytes);
If above message is reasonable I can post a new revision (v6). Thanks, Vijay
For example consider the following sequence of operations and corresponding log messages produced. Freshly booted VM with 2 nodes and 8GB memory: # cat /proc/sys/vm/min_free_kbytes 90112 # echo 90000 > /proc/sys/vm/min_free_kbytes # cat /proc/sys/vm/min_free_kbytes 90000 # echo 0 > /sys/devices/system/node/node1/memory56/online [ 135.099947] Offlined Pages 32768 [ 135.102362] min_free_kbytes is not updated to 11241 because user defined value 90000 is preferred [ 135.109070] khugepaged: raising min_free_kbytes from 90000 to 90112 to help t ransparent hugepage allocations # cat /proc/sys/vm/min_free_kbytes 90112 # echo 1 > /sys/devices/system/node/node1/memory56/online [ 231.656075] min_free_kbytes is not updated to 11334 because user defined value 90000 is preferred # cat /proc/sys/vm/min_free_kbytes 90112
