samples/damon/wsse: start and stop DAMON as the user requests

Start running DAMON to monitor accesses of a process that the user
specified via 'target_pid' parameter, when 'y' is passed to 'enable'
parameter.  Stop running DAMON when 'n' is passed to 'enable' parameter.
Estimating the working set size from DAMON's monitoring results and
reporting it to the user will be implemented by the following commit.

Link: https://lkml.kernel.org/r/20241210215030.85675-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/samples/damon/wsse.c b/samples/damon/wsse.c
index 7f2cb76a1a70a11eaf2f41d1b1124421509c1bc9..2ba0c91baad93778b1bbb2075fe80d578840401b 100644 (file)
--- a/samples/damon/wsse.c
+++ b/samples/damon/wsse.c
@@ -27,15 +27,48 @@ static bool enable __read_mostly;
 module_param_cb(enable, &enable_param_ops, &enable, 0600);
 MODULE_PARM_DESC(enable, "Enable or disable DAMON_SAMPLE_WSSE");
 
+static struct damon_ctx *ctx;
+static struct pid *target_pidp;
+
 static int damon_sample_wsse_start(void)
 {
+       struct damon_target *target;
+
        pr_info("start\n");
-       return 0;
+
+       ctx = damon_new_ctx();
+       if (!ctx)
+               return -ENOMEM;
+       if (damon_select_ops(ctx, DAMON_OPS_VADDR)) {
+               damon_destroy_ctx(ctx);
+               return -EINVAL;
+       }
+
+       target = damon_new_target();
+       if (!target) {
+               damon_destroy_ctx(ctx);
+               return -ENOMEM;
+       }
+       damon_add_target(ctx, target);
+       target_pidp = find_get_pid(target_pid);
+       if (!target_pidp) {
+               damon_destroy_ctx(ctx);
+               return -EINVAL;
+       }
+       target->pid = target_pidp;
+
+       return damon_start(&ctx, 1, true);
 }
 
 static void damon_sample_wsse_stop(void)
 {
        pr_info("stop\n");
+       if (ctx) {
+               damon_stop(&ctx, 1);
+               damon_destroy_ctx(ctx);
+       }
+       if (target_pidp)
+               put_pid(target_pidp);
 }
 
 static int damon_sample_wsse_enable_store(