Re: [PATCH] mm/damon/core: support multiple damon_call_control requests

[Enze Li <lienze@kylinos.cn>]

FTR, this is my testing patch for samples/damon/prcl.c based on tag v6.18.

8<------------------------------------------------------
diff --git a/samples/damon/prcl.c b/samples/damon/prcl.c
index b7c50f2656ce..94fd6184fb14 100644
--- a/samples/damon/prcl.c
+++ b/samples/damon/prcl.c
@@ -39,6 +39,7 @@ static int damon_sample_prcl_repeat_call_fn(void *data)
        struct damon_ctx *c = data;
        struct damon_target *t;
 
+       pr_info("repeat_call\n");
        damon_for_each_target(t, c) {
                struct damon_region *r;
                unsigned long wss = 0;
@@ -52,11 +53,22 @@ static int damon_sample_prcl_repeat_call_fn(void *data)
        return 0;
 }
 
+static int damon_sample_prcl_repeat_call_v2_fn(void *data)
+{
+       pr_info("repeat_call_v2\n");
+       return 0;
+}
+
 static struct damon_call_control repeat_call_control = {
        .fn = damon_sample_prcl_repeat_call_fn,
        .repeat = true,
 };
 
+static struct damon_call_control repeat_call_control_v2 = {
+       .fn = damon_sample_prcl_repeat_call_v2_fn,
+       .repeat = true,
+};
+
 static int damon_sample_prcl_start(void)
 {
        struct damon_target *target;
@@ -109,6 +121,9 @@ static int damon_sample_prcl_start(void)
        if (err)
                return err;
 
+       repeat_call_control_v2.data = ctx;
+       damon_call(ctx, &repeat_call_control_v2);
+
        repeat_call_control.data = ctx;
        return damon_call(ctx, &repeat_call_control);
 }
>8------------------------------------------------------

Thanks,
Enze

On Tue, Dec 02 2025 at 10:14:07 AM +0800, Enze Li wrote:

> The current implementation only supports repeated calls to a single
> damon_call_control request per context.  This limitation introduces
> inefficiencies for scenarios that require registering multiple deferred
> operations.
>
> This patch modifies the implementation of kdamond_call() to support
> repeated calls to multiple damon_call_control requests.  To demonstrate
> the effect of this change, I made minor modifications to
> samples/damon/prcl.c by adding a new request alongside the original
> damon_call_control request and performed comparative tests.
>
> Before applying the patch, I observed,
>
> [  381.661821] damon_sample_prcl: start
> [  381.668199] damon_sample_prcl: repeat_call_v2
> [  381.668208] damon_sample_prcl: repeat_call
> [  381.668211] damon_sample_prcl: wss: 0
> [  381.675194] damon_sample_prcl: repeat_call
> [  381.675202] damon_sample_prcl: wss: 0
>
> after applying the patch, I saw,
>
> [   61.750723] damon_sample_prcl: start
> [   61.757104] damon_sample_prcl: repeat_call_v2
> [   61.757106] damon_sample_prcl: repeat_call
> [   61.757107] damon_sample_prcl: wss: 0
> [   61.763067] damon_sample_prcl: repeat_call_v2
> [   61.763069] damon_sample_prcl: repeat_call
> [   61.763070] damon_sample_prcl: wss: 0
>
> Signed-off-by: Enze Li <lienze@kylinos.cn>
> ---
>  mm/damon/core.c | 20 +++++++++++++-------
>  1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/mm/damon/core.c b/mm/damon/core.c
> index 109b050c795a..66b5bae44f22 100644
> --- a/mm/damon/core.c
> +++ b/mm/damon/core.c
> @@ -2526,13 +2526,19 @@ static void kdamond_call(struct damon_ctx *ctx, bool cancel)
>  			list_add(&control->list, &repeat_controls);
>  		}
>  	}
> -	control = list_first_entry_or_null(&repeat_controls,
> -			struct damon_call_control, list);
> -	if (!control || cancel)
> -		return;
> -	mutex_lock(&ctx->call_controls_lock);
> -	list_add_tail(&control->list, &ctx->call_controls);
> -	mutex_unlock(&ctx->call_controls_lock);
> +	while (true) {
> +		control = list_first_entry_or_null(&repeat_controls,
> +				struct damon_call_control, list);
> +		if (!control)
> +			break;
> +		/* Unlink from the repeate_controls list. */
> +		list_del(&control->list);
> +		if (cancel)
> +			continue;
> +		mutex_lock(&ctx->call_controls_lock);
> +		list_add(&control->list, &ctx->call_controls);
> +		mutex_unlock(&ctx->call_controls_lock);
> +	}
>  }
>  
>  /* Returns negative error code if it's not activated but should return */
>
> base-commit: 7d0a66e4bb9081d75c82ec4957c50034cb0ea449