From e5d64edac64531375716fabe35c9e0a502ca2894 Mon Sep 17 00:00:00 2001 From: Yosry Ahmed Date: Fri, 2 Dec 2022 03:15:11 +0000 Subject: [PATCH] selftests: cgroup: refactor proactive reclaim code to reclaim_until() 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. Link: https://lkml.kernel.org/r/20221202031512.1365483-3-yosryahmed@google.com Signed-off-by: Yosry Ahmed Suggested-by: Roman Gushchin Reviewed-by: Roman Gushchin Cc: Chris Down Cc: David Rientjes Cc: Johannes Weiner Cc: Matthew Wilcox Cc: Michal Hocko Cc: Muchun Song Cc: Shakeel Butt Cc: Tejun Heo Cc: Vasily Averin Cc: Vlastimil Babka Cc: Yu Zhao Signed-off-by: Andrew Morton --- tools/testing/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 8833359..a8f4700 100644 --- a/tools/testing/selftests/cgroup/test_memcontrol.c +++ b/tools/testing/selftests/cgroup/test_memcontrol.c @@ -646,6 +646,48 @@ cleanup: } /* + * 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: -- 2.7.4