Refactor the code that drives writing to memory.reclaim (retrying, error
handling, etc) from test_memcg_reclaim() to a helper called
reclaim_until(), which proactively reclaims from a memcg until its
usage reaches a certain value.
While we are at it, refactor and simplify the reclaim loop.
This will be used in a following patch in another test.
Signed-off-by: Yosry Ahmed <[email protected]>
Suggested-by: Roman Gushchin <[email protected]>
---
.../selftests/cgroup/test_memcontrol.c | 80 ++++++++++---------
1 file changed, 44 insertions(+), 36 deletions(-)
diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c
index 8833359556f3..a8f4700353a4 100644
--- a/tools/testing/selftests/cgroup/test_memcontrol.c
+++ b/tools/testing/selftests/cgroup/test_memcontrol.c
@@ -645,6 +645,48 @@ static int test_memcg_max(const char *root)
return ret;
}
+/*
+ * Reclaim from @memcg until usage reaches @goal by writing to
+ * memory.reclaim.
+ *
+ * This function will return false if the usage is already below the
+ * goal.
+ *
+ * This function assumes that writing to memory.reclaim is the only
+ * source of change in memory.current (no concurrent allocations or
+ * reclaim).
+ *
+ * This function makes sure memory.reclaim is sane. It will return
+ * false if memory.reclaim's error codes do not make sense, even if
+ * the usage goal was satisfied.
+ */
+static bool reclaim_until(const char *memcg, long goal)
+{
+ char buf[64];
+ int retries, err;
+ long current, to_reclaim;
+ bool reclaimed = false;
+
+ for (retries = 5; retries > 0; retries--) {
+ current = cg_read_long(memcg, "memory.current");
+
+ if (current < goal || values_close(current, goal, 3))
+ break;
+ /* Did memory.reclaim return 0 incorrectly? */
+ else if (reclaimed)
+ return false;
+
+ to_reclaim = current - goal;
+ snprintf(buf, sizeof(buf), "%ld", to_reclaim);
+ err = cg_write(memcg, "memory.reclaim", buf);
+ if (!err)
+ reclaimed = true;
+ else if (err != -EAGAIN)
+ return false;
+ }
+ return reclaimed;
+}
+
/*
* This test checks that memory.reclaim reclaims the given
* amount of memory (from both anon and file, if possible).
@@ -653,8 +695,7 @@ static int test_memcg_reclaim(const char *root)
{
int ret = KSFT_FAIL, fd, retries;
char *memcg;
- long current, expected_usage, to_reclaim;
- char buf[64];
+ long current, expected_usage;
memcg = cg_name(root, "memcg_test");
if (!memcg)
@@ -705,41 +746,8 @@ static int test_memcg_reclaim(const char *root)
* Reclaim until current reaches 30M, this makes sure we hit both anon
* and file if swap is enabled.
*/
- retries = 5;
- while (true) {
- int err;
-
- current = cg_read_long(memcg, "memory.current");
- to_reclaim = current - MB(30);
-
- /*
- * We only keep looping if we get EAGAIN, which means we could
- * not reclaim the full amount.
- */
- if (to_reclaim <= 0)
- goto cleanup;
-
-
- snprintf(buf, sizeof(buf), "%ld", to_reclaim);
- err = cg_write(memcg, "memory.reclaim", buf);
- if (!err) {
- /*
- * If writing succeeds, then the written amount should have been
- * fully reclaimed (and maybe more).
- */
- current = cg_read_long(memcg, "memory.current");
- if (!values_close(current, MB(30), 3) && current > MB(30))
- goto cleanup;
- break;
- }
-
- /* The kernel could not reclaim the full amount, try again. */
- if (err == -EAGAIN && retries--)
- continue;
-
- /* We got an unexpected error or ran out of retries. */
+ if (!reclaim_until(memcg, MB(30)))
goto cleanup;
- }
ret = KSFT_PASS;
cleanup:
--
2.39.0.rc0.267.gcb52ba06e7-goog
On Fri, Dec 02, 2022 at 03:15:11AM +0000, Yosry Ahmed wrote:
> Refactor the code that drives writing to memory.reclaim (retrying, error
> handling, etc) from test_memcg_reclaim() to a helper called
> reclaim_until(), which proactively reclaims from a memcg until its
> usage reaches a certain value.
>
> While we are at it, refactor and simplify the reclaim loop.
>
> This will be used in a following patch in another test.
>
> Signed-off-by: Yosry Ahmed <[email protected]>
> Suggested-by: Roman Gushchin <[email protected]>
Reviewed-by: Roman Gushchin <[email protected]>
Thanks!