[PATCH] samples/damon: add parameters for node0 memory usage

[Yunjeong Mun]

This patch changes the hard-coded quota goal metric values into sysfs
knobs: `node0_mem_used_bp` and `node0_mem_free_bp`. These knobs
represent the used and free memory ratio of node0 in basis points
(bp, where 1 bp = 0.01%). As mentioned in [1], this patch is developed
under the assumption that node0 is always the fast-tier in a two-tiers
memory setup.

[1] https://lore.kernel.org/linux-mm/20250420194030.75838-8-sj@xxxxxxxxxx/

Suggested-by: Honggyu Kim <honggyu.kim@xxxxxx>
Signed-off-by: Yunjeong Mun <yunjeong.mun@xxxxxx>
---
 samples/damon/mtier.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/samples/damon/mtier.c b/samples/damon/mtier.c
index 36d2cd933f5a..f3220d6e6739 100644
--- a/samples/damon/mtier.c
+++ b/samples/damon/mtier.c
@@ -24,6 +24,12 @@ module_param(node1_start_addr, ulong, 0600);
 static unsigned long node1_end_addr __read_mostly;
 module_param(node1_end_addr, ulong, 0600);
 
+static unsigned long node0_mem_used_bp __read_mostly = 9970;
+module_param(node0_mem_used_bp, ulong, 0600);
+
+static unsigned long node0_mem_free_bp __read_mostly = 50;
+module_param(node0_mem_free_bp, ulong, 0600);
+
 static int damon_sample_mtier_enable_store(
 		const char *val, const struct kernel_param *kp);
 
@@ -112,7 +118,7 @@ static struct damon_ctx *damon_sample_mtier_build_ctx(bool promote)
 	quota_goal = damos_new_quota_goal(
 			promote ? DAMOS_QUOTA_NODE_MEM_USED_BP :
 			DAMOS_QUOTA_NODE_MEM_FREE_BP,
-			promote ? 9970 : 50);
+			promote ? node0_mem_used_bp : node0_mem_free_bp);
 	if (!quota_goal)
 		goto free_out;
 	quota_goal->nid = 0;
-- 
2.34.1