mm/damon/schemes: implement size quota for schemes application speed control

There could be arbitrarily large memory regions fulfilling the target
data access pattern of a DAMON-based operation scheme.  In the case,
applying the action of the scheme could incur too high overhead.  To
provide an intuitive way for avoiding it, this implements a feature
called size quota.  If the quota is set, DAMON tries to apply the action
only up to the given amount of memory regions within a given time
window.

Link: https://lkml.kernel.org/r/20211019150731.16699-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Leonard Foerster <foersleo@amazon.de>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index c90988a20fa4..a04bd50cc4c4 100644
--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -188,6 +188,8 @@ static struct damos **str_to_schemes(const char *str, ssize_t len,
 
 	*nr_schemes = 0;
 	while (pos < len && *nr_schemes < max_nr_schemes) {
+		struct damos_quota quota = {};
+
 		ret = sscanf(&str[pos], "%lu %lu %u %u %u %u %u%n",
 				&min_sz, &max_sz, &min_nr_a, &max_nr_a,
 				&min_age, &max_age, &action, &parsed);
@@ -200,7 +202,7 @@ static struct damos **str_to_schemes(const char *str, ssize_t len,
 
 		pos += parsed;
 		scheme = damon_new_scheme(min_sz, max_sz, min_nr_a, max_nr_a,
-				min_age, max_age, action);
+				min_age, max_age, action, &quota);
 		if (!scheme)
 			goto fail;