mm/damon/schemes: skip already charged targets and regions

If DAMOS has stopped applying action in the middle of a group of memory
regions due to its size quota, it starts the work again from the
beginning of the address space in the next charge window.  If there is a
huge memory region at the beginning of the address space and it fulfills
the scheme's target data access pattern always, the action will applied
to only the region.

This mitigates the case by skipping memory regions that charged in
current charge window at the beginning of next charge window.

Link: https://lkml.kernel.org/r/20211019150731.16699-4-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, 37 insertions, 0 deletions

diff --git a/mm/damon/core.c b/mm/damon/core.c
index cce14a0d5c72..693b75bc3450 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -111,6 +111,8 @@ struct damos *damon_new_scheme(
 	scheme->quota.reset_interval = quota->reset_interval;
 	scheme->quota.charged_sz = 0;
 	scheme->quota.charged_from = 0;
+	scheme->quota.charge_target_from = NULL;
+	scheme->quota.charge_addr_from = 0;
 
 	return scheme;
 }
@@ -553,6 +555,37 @@ static void damon_do_apply_schemes(struct damon_ctx *c,
 		if (quota->sz && quota->charged_sz >= quota->sz)
 			continue;
 
+		/* Skip previously charged regions */
+		if (quota->charge_target_from) {
+			if (t != quota->charge_target_from)
+				continue;
+			if (r == damon_last_region(t)) {
+				quota->charge_target_from = NULL;
+				quota->charge_addr_from = 0;
+				continue;
+			}
+			if (quota->charge_addr_from &&
+					r->ar.end <= quota->charge_addr_from)
+				continue;
+
+			if (quota->charge_addr_from && r->ar.start <
+					quota->charge_addr_from) {
+				sz = ALIGN_DOWN(quota->charge_addr_from -
+						r->ar.start, DAMON_MIN_REGION);
+				if (!sz) {
+					if (r->ar.end - r->ar.start <=
+							DAMON_MIN_REGION)
+						continue;
+					sz = DAMON_MIN_REGION;
+				}
+				damon_split_region_at(c, t, r, sz);
+				r = damon_next_region(r);
+				sz = r->ar.end - r->ar.start;
+			}
+			quota->charge_target_from = NULL;
+			quota->charge_addr_from = 0;
+		}
+
 		/* Check the target regions condition */
 		if (sz < s->min_sz_region || s->max_sz_region < sz)
 			continue;
@@ -573,6 +606,10 @@ static void damon_do_apply_schemes(struct damon_ctx *c,
 			}
 			c->primitive.apply_scheme(c, t, r, s);
 			quota->charged_sz += sz;
+			if (quota->sz && quota->charged_sz >= quota->sz) {
+				quota->charge_target_from = t;
+				quota->charge_addr_from = r->ar.end + 1;
+			}
 		}
 		if (s->action != DAMOS_STAT)
 			r->age = 0;