linux-kernel - Re: [PATCH v4 4/4] selftests: cgroup: add a selftest for memory.reclaim

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20220423142801.gnvd42cdcsz4hpon@google.com>
Date:   Sat, 23 Apr 2022 14:28:01 +0000
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Yosry Ahmed <yosryahmed@...gle.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        David Rientjes <rientjes@...gle.com>,
        Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
        Jonathan Corbet <corbet@....net>,
        Shuah Khan <shuah@...nel.org>, Yu Zhao <yuzhao@...gle.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Wei Xu <weixugc@...gle.com>, Greg Thelen <gthelen@...gle.com>,
        Chen Wandun <chenwandun@...wei.com>,
        Vaibhav Jain <vaibhav@...ux.ibm.com>,
        "Michal Koutný" <mkoutny@...e.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Dan Schatzberg <schatzberg.dan@...il.com>,
        cgroups@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v4 4/4] selftests: cgroup: add a selftest for memory.reclaim

On Thu, Apr 21, 2022 at 11:44:26PM +0000, Yosry Ahmed wrote:
> 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@...gle.com>
> Acked-by: Roman Gushchin <roman.gushchin@...ux.dev>
> ---
>  .../selftests/cgroup/test_memcontrol.c        | 86 +++++++++++++++++++
>  1 file changed, 86 insertions(+)
> 
> diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c
> index f2ffb3a30194..5f7c20de2426 100644
> --- a/tools/testing/selftests/cgroup/test_memcontrol.c
> +++ b/tools/testing/selftests/cgroup/test_memcontrol.c
> @@ -760,6 +760,91 @@ 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).
> + */
> +static int test_memcg_reclaim(const char *root)
> +{
> +	int ret = KSFT_FAIL, fd, retries;
> +	char *memcg;
> +	long current, 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;
> +
> +	cg_run_nowait(memcg, alloc_anon_noexit, (void *) MB(50));

Don't you need is_swap_enabled() check before deciding to do the anon
allocations?

> +	sleep(1);
> +
> +	fd = get_temp_fd();
> +	if (fd < 0)
> +		goto cleanup;
> +
> +	cg_run_nowait(memcg, alloc_pagecache_50M_noexit, (void *)(long)fd);
> +	sleep(1);

These sleep(1)s do not seem robust. Since kernel keeps the page cache
around, you can convert anon to use tmpfs and use simple cg_run to
trigger the allocations of anon (tmpfs) and file which will remain in
memory even after return from cg_run.