[PATCH v5 4/4] selftests: cgroup: add a selftest for memory.reclaim

Yosry Ahmed
2022-04-25T19:01:18Z

Add a new test for memory.reclaim that verifies that the interface
correctly reclaims memory as intended, from both anon and file pages.

Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
---
.../selftests/cgroup/test_memcontrol.c | 106 ++++++++++++++++++
1 file changed, 106 insertions(+)

diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c
index f2ffb3a30194..a9c691fb94c0 100644
--- a/tools/testing/selftests/cgroup/test_memcontrol.c
+++ b/tools/testing/selftests/cgroup/test_memcontrol.c
@@ -760,6 +760,111 @@ static int test_memcg_max(const char *root)
return ret;
}

+/*
+ * This test checks that memory.reclaim reclaims the given
+ * amount of memory (from both anon and file, if possible).
+ */
+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];
+
+ memcg = cg_name(root, "memcg_test");
+ if (!memcg)
+ goto cleanup;
+
+ if (cg_create(memcg))
+ goto cleanup;
+
+ current = cg_read_long(memcg, "memory.current");
+ if (current != 0)
+ goto cleanup;
+
+ fd = get_temp_fd();
+ if (fd < 0)
+ goto cleanup;
+
+ cg_run_nowait(memcg, alloc_pagecache_50M_noexit, (void *)(long)fd);
+
+ /*
+ * If swap is enabled, try to reclaim from both anon and file, else try
+ * to reclaim from file only.
+ */
+ if (is_swap_enabled()) {
+ cg_run_nowait(memcg, alloc_anon_noexit, (void *) MB(50));
+ expected_usage = MB(100);
+ } else
+ expected_usage = MB(50);
+
+ /*
+ * Wait until current usage reaches the expected usage (or we run out of
+ * retries).
+ */
+ retries = 5;
+ while (!values_close(cg_read_long(memcg, "memory.current"),
+ expected_usage, 10)) {
+ if (retries--) {
+ sleep(1);
+ continue;
+ } else {
+ fprintf(stderr,
+ "failed to allocate %ld for memcg reclaim test\n",
+ expected_usage);
+ goto cleanup;
+ }
+ }
+
+ /*
+ * 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. */
+ goto cleanup;
+ }
+
+ ret = KSFT_PASS;
+cleanup:
+ cg_destroy(memcg);
+ free(memcg);
+ close(fd);
+
+ return ret;
+}
+
static int alloc_anon_50M_check_swap(const char *cgroup, void *arg)
{
long mem_max = (long)arg;
@@ -1263,6 +1368,7 @@ struct memcg_test {
T(test_memcg_high),
T(test_memcg_high_sync),
T(test_memcg_max),
+ T(test_memcg_reclaim),
T(test_memcg_oom_events),
T(test_memcg_swap_max),
T(test_memcg_sock),
--
2.36.0.rc2.479.g8af0fa9b8e-goog