Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH] selftests: memory-hotplug: avoid spamming logs with
 dump_page(), ratio limit hot-remove error test
To:     Paolo Pisati <paolo.pisati@canonical.com>,
        Shuah Khan <shuah@kernel.org>
Cc:     linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20210630145740.54614-1-paolo.pisati@canonical.com>
From:   Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Message-ID: <1881c379-d752-6850-1a1a-fd217eb4a661@canonical.com>
Date:   Fri, 2 Jul 2021 16:48:32 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.11.0
MIME-Version: 1.0
In-Reply-To: <20210630145740.54614-1-paolo.pisati@canonical.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 30/06/2021 16:57, Paolo Pisati wrote:
> While the offline memory test obey ratio limit, the same test with error
> injection does not and tries to offline all the hotpluggable memory, spamming
> system logs with hundreds of thousands of dump_page() entries, slowing system
> down (to the point the test itself timeout and gets terminated) and excessive fs
> occupation:
> 
> ...
> [ 9784.393354] page:c00c0000007d1b40 refcount:3 mapcount:0 mapping:c0000001fc03e950 index:0xe7b
> [ 9784.393355] def_blk_aops
> [ 9784.393356] flags: 0x3ffff800002062(referenced|active|workingset|private)
> [ 9784.393358] raw: 003ffff800002062 c0000001b9343a68 c0000001b9343a68 c0000001fc03e950
> [ 9784.393359] raw: 0000000000000e7b c000000006607b18 00000003ffffffff c00000000490d000
> [ 9784.393359] page dumped because: migration failure
> [ 9784.393360] page->mem_cgroup:c00000000490d000
> [ 9784.393416] migrating pfn 1f46d failed ret:1
> ...
> 
> $ grep "page dumped because: migration failure" /var/log/kern.log | wc -l
> 2405558
> 
> $ ls -la /var/log/kern.log
> -rw-r----- 1 syslog adm 2256109539 Jun 30 14:19 /var/log/kern.log

Makes sense to me and looks better choice than to disable the test
completely (as other choice...).

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>

> 
> Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>
> ---
>  tools/testing/selftests/memory-hotplug/mem-on-off-test.sh | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
Best regards,
Krzysztof