2022-04-22 18:35:05

by Yosry Ahmed

Subject: [PATCH v4 3/4] selftests: cgroup: fix alloc_anon_noexit() instantly freeing memory

Currently, alloc_anon_noexit() calls alloc_anon() which instantly frees
the allocated memory. alloc_anon_noexit() is usually used with
cg_run_nowait() to run a process in the background that allocates
memory. It makes sense for the background process to keep the memory
allocated and not instantly free it (otherwise there is no point of
running it in the background).

Signed-off-by: Yosry Ahmed <[email protected]>
Acked-by: Roman Gushchin <[email protected]>
---
tools/testing/selftests/cgroup/test_memcontrol.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c
index 36ccf2322e21..f2ffb3a30194 100644
--- a/tools/testing/selftests/cgroup/test_memcontrol.c
+++ b/tools/testing/selftests/cgroup/test_memcontrol.c
@@ -211,13 +211,17 @@ static int alloc_pagecache_50M_noexit(const char *cgroup, void *arg)
static int alloc_anon_noexit(const char *cgroup, void *arg)
{
int ppid = getppid();
+ size_t size = (unsigned long)arg;
+ char *buf, *ptr;

- if (alloc_anon(cgroup, arg))
- return -1;
+ buf = malloc(size);
+ for (ptr = buf; ptr < buf + size; ptr += PAGE_SIZE)
+ *ptr = 0;

while (getppid() == ppid)
sleep(1);

+ free(buf);
return 0;
}

--
2.36.0.rc2.479.g8af0fa9b8e-goog

2022-04-24 16:39:37

by Shakeel Butt

Subject: Re: [PATCH v4 3/4] selftests: cgroup: fix alloc_anon_noexit() instantly freeing memory

On Thu, Apr 21, 2022 at 11:44:25PM +0000, Yosry Ahmed wrote:
> Currently, alloc_anon_noexit() calls alloc_anon() which instantly frees
> the allocated memory. alloc_anon_noexit() is usually used with
> cg_run_nowait() to run a process in the background that allocates
> memory. It makes sense for the background process to keep the memory
> allocated and not instantly free it (otherwise there is no point of
> running it in the background).
>
> Signed-off-by: Yosry Ahmed <[email protected]>
> Acked-by: Roman Gushchin <[email protected]>

Acked-by: Shakeel Butt <[email protected]>