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Message-ID: <20240823162506.12117-2-me@yhndnzj.com>
Date: Fri, 23 Aug 2024 16:27:09 +0000
From: Mike Yuan <me@...dnzj.com>
To: linux-kernel@...r.kernel.org
Cc: Mike Yuan <me@...dnzj.com>, linux-mm@...ck.org, cgroups@...r.kernel.org, Nhat Pham <nphamcs@...il.com>, Yosry Ahmed <yosryahmed@...gle.com>, Johannes Weiner <hannes@...xchg.org>, Andrew Morton <akpm@...ux-foundation.org>, Muchun Song <muchun.song@...ux.dev>, Shakeel Butt <shakeel.butt@...ux.dev>, Roman Gushchin <roman.gushchin@...ux.dev>, Michal Hocko <mhocko@...nel.org>
Subject: [PATCH v3 2/3] selftests: test_zswap: add test for hierarchical zswap.writeback
Ensure that zswap.writeback check goes up the cgroup tree, i.e.
is hierarchical. Create a subcgroup which has zswap.writeback
set to 1, and the upper hierarchy's restrictions shall apply.
Changes in v3:
- Skip the zswap.writeback test if root cgroup has it disabled
(I still think adding a whole new test is a bit of overkill,
though, instead came up with this alternative approach)
- Add comment about hardcoding child cg's zswap.writeback=1
which might not be obvious
Link to v2: https://lore.kernel.org/all/20240816144344.18135-2-me@yhndnzj.com/
Signed-off-by: Mike Yuan <me@...dnzj.com>
---
tools/testing/selftests/cgroup/test_zswap.c | 75 +++++++++++++++------
1 file changed, 54 insertions(+), 21 deletions(-)
diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/selftests/cgroup/test_zswap.c
index 190096017f80..40de679248b8 100644
--- a/tools/testing/selftests/cgroup/test_zswap.c
+++ b/tools/testing/selftests/cgroup/test_zswap.c
@@ -263,15 +263,13 @@ static int test_zswapin(const char *root)
static int attempt_writeback(const char *cgroup, void *arg)
{
long pagesize = sysconf(_SC_PAGESIZE);
- char *test_group = arg;
size_t memsize = MB(4);
char buf[pagesize];
long zswap_usage;
- bool wb_enabled;
+ bool wb_enabled = *(bool *) arg;
int ret = -1;
char *mem;
- wb_enabled = cg_read_long(test_group, "memory.zswap.writeback");
mem = (char *)malloc(memsize);
if (!mem)
return ret;
@@ -288,12 +286,12 @@ static int attempt_writeback(const char *cgroup, void *arg)
memcpy(&mem[i], buf, pagesize);
/* Try and reclaim allocated memory */
- if (cg_write_numeric(test_group, "memory.reclaim", memsize)) {
+ if (cg_write_numeric(cgroup, "memory.reclaim", memsize)) {
ksft_print_msg("Failed to reclaim all of the requested memory\n");
goto out;
}
- zswap_usage = cg_read_long(test_group, "memory.zswap.current");
+ zswap_usage = cg_read_long(cgroup, "memory.zswap.current");
/* zswpin */
for (int i = 0; i < memsize; i += pagesize) {
@@ -303,7 +301,7 @@ static int attempt_writeback(const char *cgroup, void *arg)
}
}
- if (cg_write_numeric(test_group, "memory.zswap.max", zswap_usage/2))
+ if (cg_write_numeric(cgroup, "memory.zswap.max", zswap_usage/2))
goto out;
/*
@@ -312,7 +310,7 @@ static int attempt_writeback(const char *cgroup, void *arg)
* If writeback is disabled, memory reclaim will fail as zswap is limited and
* it can't writeback to swap.
*/
- ret = cg_write_numeric(test_group, "memory.reclaim", memsize);
+ ret = cg_write_numeric(cgroup, "memory.reclaim", memsize);
if (!wb_enabled)
ret = (ret == -EAGAIN) ? 0 : -1;
@@ -321,12 +319,41 @@ static int attempt_writeback(const char *cgroup, void *arg)
return ret;
}
+static int test_zswap_writeback_one(const char *cgroup, bool wb)
+{
+ long zswpwb_before, zswpwb_after;
+
+ zswpwb_before = get_cg_wb_count(cgroup);
+ if (zswpwb_before != 0) {
+ ksft_print_msg("zswpwb_before = %ld instead of 0\n", zswpwb_before);
+ return -1;
+ }
+
+ if (cg_run(cgroup, attempt_writeback, (void *) &wb))
+ return -1;
+
+ /* Verify that zswap writeback occurred only if writeback was enabled */
+ zswpwb_after = get_cg_wb_count(cgroup);
+ if (zswpwb_after < 0)
+ return -1;
+
+ if (wb != !!zswpwb_after) {
+ ksft_print_msg("zswpwb_after is %ld while wb is %s",
+ zswpwb_after, wb ? "enabled" : "disabled");
+ return -1;
+ }
+
+ return 0;
+}
+
/* Test to verify the zswap writeback path */
static int test_zswap_writeback(const char *root, bool wb)
{
- long zswpwb_before, zswpwb_after;
int ret = KSFT_FAIL;
- char *test_group;
+ char *test_group, *test_group_child = NULL;
+
+ if (cg_read_strcmp(root, "memory.zswap.writeback", "1"))
+ return KSFT_SKIP;
test_group = cg_name(root, "zswap_writeback_test");
if (!test_group)
@@ -336,29 +363,35 @@ static int test_zswap_writeback(const char *root, bool wb)
if (cg_write(test_group, "memory.zswap.writeback", wb ? "1" : "0"))
goto out;
- zswpwb_before = get_cg_wb_count(test_group);
- if (zswpwb_before != 0) {
- ksft_print_msg("zswpwb_before = %ld instead of 0\n", zswpwb_before);
+ if (test_zswap_writeback_one(test_group, wb))
goto out;
- }
- if (cg_run(test_group, attempt_writeback, (void *) test_group))
+ /* Reset memory.zswap.max to max (modified by attempt_writeback), and
+ * set up child cgroup, whose memory.zswap.writeback is hardcoded to 1.
+ * Thus, the parent's setting shall be what's in effect. */
+ if (cg_write(test_group, "memory.zswap.max", "max"))
+ goto out;
+ if (cg_write(test_group, "cgroup.subtree_control", "+memory"))
goto out;
- /* Verify that zswap writeback occurred only if writeback was enabled */
- zswpwb_after = get_cg_wb_count(test_group);
- if (zswpwb_after < 0)
+ test_group_child = cg_name(test_group, "zswap_writeback_test_child");
+ if (!test_group_child)
+ goto out;
+ if (cg_create(test_group_child))
+ goto out;
+ if (cg_write(test_group_child, "memory.zswap.writeback", "1"))
goto out;
- if (wb != !!zswpwb_after) {
- ksft_print_msg("zswpwb_after is %ld while wb is %s",
- zswpwb_after, wb ? "enabled" : "disabled");
+ if (test_zswap_writeback_one(test_group_child, wb))
goto out;
- }
ret = KSFT_PASS;
out:
+ if (test_group_child) {
+ cg_destroy(test_group_child);
+ free(test_group_child);
+ }
cg_destroy(test_group);
free(test_group);
return ret;
--
2.46.0
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