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From:   SeongJae Park <sjpark@amazon.com>
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Subject: [PATCH v8 07/15] mm/damon: Implement callbacks
Date:   Mon, 6 Apr 2020 15:09:30 +0200
Message-ID: <20200406130938.14066-8-sjpark@amazon.com>
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From: SeongJae Park <sjpark@amazon.de>

This commit implements callbacks for DAMON.  Using this, DAMON users can
install their callbacks for each step of the access monitoring so that
they can do something interesting with the monitored access patterns
online.  For example, callbacks can report the monitored patterns to
users or do some access pattern based memory management such as
proactive reclamations or access pattern based THP promotions/demotions
decision makings.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
---
 include/linux/damon.h | 4 ++++
 mm/damon.c            | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 64e327400749..cad3ee3d78db 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -56,6 +56,10 @@ struct damon_ctx {
 	struct rnd_state rndseed;
 
 	struct list_head tasks_list;	/* 'damon_task' objects */
+
+	/* callbacks */
+	void (*sample_cb)(struct damon_ctx *context);
+	void (*aggregate_cb)(struct damon_ctx *context);
 };
 
 int damon_set_pids(struct damon_ctx *ctx, unsigned long *pids, ssize_t nr_pids);
diff --git a/mm/damon.c b/mm/damon.c
index acbcd702ef0c..608787e88118 100644
--- a/mm/damon.c
+++ b/mm/damon.c
@@ -821,6 +821,8 @@ static int kdamond_fn(void *data)
 	kdamond_init_regions(ctx);
 	while (!kdamond_need_stop(ctx)) {
 		kdamond_prepare_access_checks(ctx);
+		if (ctx->sample_cb)
+			ctx->sample_cb(ctx);
 
 		usleep_range(ctx->sample_interval, ctx->sample_interval + 1);
 
@@ -828,6 +830,8 @@ static int kdamond_fn(void *data)
 
 		if (kdamond_aggregate_interval_passed(ctx)) {
 			kdamond_merge_regions(ctx, max_nr_accesses / 10);
+			if (ctx->aggregate_cb)
+				ctx->aggregate_cb(ctx);
 			kdamond_reset_aggregated(ctx);
 			kdamond_split_regions(ctx);
 		}
-- 
2.17.1