Subject should be something like:
mm/compaction: Make proactive compaction high watermark configurable via sysctl
On Fri, Jan 24, 2025 at 1:21 PM Michal Clapinski <mclapinski@xxxxxxxxxx> wrote:
>
> Expose the diff between low and high watermark as a sysctl var.
Please expand, for example:
Currently, the difference between the low and high watermarks for
proactive compaction is hardcoded to 10. This hardcoded difference is
too large for free page reporting to work correctly.
Add a new sysctl, `compaction_proactiveness_leeway`, to control the
difference between the low and high watermarks.
Pasha
>
> Signed-off-by: Michal Clapinski <mclapinski@xxxxxxxxxx>
> ---
> mm/compaction.c | 12 +++++++++++-
> 1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 29524242a16ef..fd546b797e544 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1921,6 +1921,7 @@ static int sysctl_compact_unevictable_allowed __read_mostly = CONFIG_COMPACT_UNE
> * background. It takes values in the range [0, 100].
> */
> static unsigned int __read_mostly sysctl_compaction_proactiveness = 20;
> +static unsigned int __read_mostly sysctl_compaction_proactiveness_leeway = 10;
> static int sysctl_extfrag_threshold = 500;
> static int __read_mostly sysctl_compact_memory;
>
> @@ -2254,7 +2255,7 @@ static unsigned int fragmentation_score_wmark(bool low)
> * close to 100 (maximum).
> */
> wmark_low = 100U - sysctl_compaction_proactiveness;
> - return low ? wmark_low : min(wmark_low + 10, 100U);
> + return low ? wmark_low : min(wmark_low + sysctl_compaction_proactiveness_leeway, 100U);
> }
>
> static bool should_proactive_compact_node(pg_data_t *pgdat)
> @@ -3314,6 +3315,15 @@ static struct ctl_table vm_compaction[] = {
> .extra1 = SYSCTL_ZERO,
> .extra2 = SYSCTL_ONE_HUNDRED,
> },
> + {
> + .procname = "compaction_proactiveness_leeway",
> + .data = &sysctl_compaction_proactiveness_leeway,
> + .maxlen = sizeof(sysctl_compaction_proactiveness_leeway),
> + .mode = 0644,
> + .proc_handler = compaction_proactiveness_sysctl_handler,
> + .extra1 = SYSCTL_ZERO,
> + .extra2 = SYSCTL_ONE_HUNDRED,
> + },
> {
> .procname = "extfrag_threshold",
> .data = &sysctl_extfrag_threshold,
> --
> 2.48.1.262.g85cc9f2d1e-goog
>
>
