From 43df7676e5508895c33b846d37cff9cf3b52674c Mon Sep 17 00:00:00 2001 From: SeongJae Park Date: Sat, 12 Jul 2025 12:50:04 -0700 Subject: [PATCH] mm/damon/core: introduce repeat mode damon_call() damon_call() can be useful for reading or writing DAMON internal data for one time. A common pattern of DAMON core usage from DAMON modules is doing such reads and writes repeatedly, for example, to periodically update the DAMOS stats. To do that with damon_call(), callers should call damon_call() repeatedly, with their own delay loop. Each caller doing that is repetitive. Introduce a repeat mode damon_call(). Callers can use the mode by setting a new field in damon_call_control. If the mode is turned on, damon_call() returns success immediately, and DAMON repeats invoking the callback function inside the kdamond main loop. Link: https://lkml.kernel.org/r/20250712195016.151108-3-sj@kernel.org Signed-off-by: SeongJae Park Signed-off-by: Andrew Morton --- include/linux/damon.h | 2 ++ mm/damon/core.c | 25 ++++++++++++++++++++----- 2 files changed, 22 insertions(+), 5 deletions(-) diff --git a/include/linux/damon.h b/include/linux/damon.h index 562c7876ba88f..b83987275ff9d 100644 --- a/include/linux/damon.h +++ b/include/linux/damon.h @@ -659,6 +659,7 @@ struct damon_callback { * * @fn: Function to be called back. * @data: Data that will be passed to @fn. + * @repeat: Repeat invocations. * @return_code: Return code from @fn invocation. * * Control damon_call(), which requests specific kdamond to invoke a given @@ -667,6 +668,7 @@ struct damon_callback { struct damon_call_control { int (*fn)(void *data); void *data; + bool repeat; int return_code; /* private: internal use only */ /* informs if the kdamond finished handling of the request */ diff --git a/mm/damon/core.c b/mm/damon/core.c index b0a0b98f68898..ffb87497dbb5e 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -1379,8 +1379,9 @@ bool damon_is_running(struct damon_ctx *ctx) * * Ask DAMON worker thread (kdamond) of @ctx to call a function with an * argument data that respectively passed via &damon_call_control->fn and - * &damon_call_control->data of @control, and wait until the kdamond finishes - * handling of the request. + * &damon_call_control->data of @control. If &damon_call_control->repeat of + * @control is set, further wait until the kdamond finishes handling of the + * request. Otherwise, return as soon as the request is made. * * The kdamond executes the function with the argument in the main loop, just * after a sampling of the iteration is finished. The function can hence @@ -1392,7 +1393,8 @@ bool damon_is_running(struct damon_ctx *ctx) */ int damon_call(struct damon_ctx *ctx, struct damon_call_control *control) { - init_completion(&control->completion); + if (!control->repeat) + init_completion(&control->completion); control->canceled = false; INIT_LIST_HEAD(&control->list); @@ -1401,6 +1403,8 @@ int damon_call(struct damon_ctx *ctx, struct damon_call_control *control) mutex_unlock(&ctx->call_controls_lock); if (!damon_is_running(ctx)) return -EINVAL; + if (control->repeat) + return 0; wait_for_completion(&control->completion); if (control->canceled) return -ECANCELED; @@ -2429,6 +2433,7 @@ static void kdamond_usleep(unsigned long usecs) static void kdamond_call(struct damon_ctx *ctx, bool cancel) { struct damon_call_control *control; + LIST_HEAD(repeat_controls); int ret = 0; while (true) { @@ -2437,7 +2442,7 @@ static void kdamond_call(struct damon_ctx *ctx, bool cancel) struct damon_call_control, list); mutex_unlock(&ctx->call_controls_lock); if (!control) - return; + break; if (cancel) { control->canceled = true; } else { @@ -2447,8 +2452,18 @@ static void kdamond_call(struct damon_ctx *ctx, bool cancel) mutex_lock(&ctx->call_controls_lock); list_del(&control->list); mutex_unlock(&ctx->call_controls_lock); - complete(&control->completion); + if (!control->repeat) + complete(&control->completion); + else + 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); } /* Returns negative error code if it's not activated but should return */ -- 2.47.2