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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 <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
SeongJae Park 2025-07-12 12:50:04 -07:00 committed by Andrew Morton
parent 004ded6bee
commit 43df7676e5
2 changed files with 22 additions and 5 deletions
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2
include/linux/damon.h
View File

@ -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 */

21
mm/damon/core.c
View File

@ -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
@ -1392,6 +1393,7 @@ bool damon_is_running(struct damon_ctx *ctx)
*/
int damon_call(struct damon_ctx *ctx, struct damon_call_control *control)
{
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);
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 */