[PATCH] [act] UBUNTU: SAUCE: ubuntu_kernel_selftests: disable memory-hotplug

[Krzysztof Kozlowski]

On 23/06/2021 15:13, Paolo Pisati wrote:
> The memory-hotplug test has been intermittently timing out (or trashing the test
> VM, see below) on Impish/Hirsute ppc64el and x86-64 for quite some time now.
> 
> Upon further investigation, we found that memory-hotplug has a tendency to spam
> the system logs (kernel.log, syslog and the systemd-journal) with thousands and
> thousands (up to several GBs) of dump_page() entries like this:

Azure will have it disabled with (already applied):
https://bugs.launchpad.net/ubuntu-kernel-tests/+bug/1897764

> 
> ...
> [  898.286185] migrating pfn 11c462 failed ret:1
> [  898.286186] page:00000000491a3636 refcount:3 mapcount:0 mapping:00000000e646cbed index:0xc00066 pfn:0x11c462
> [  898.286188] memcg:ffff947290991000
> [  898.286188] aops:def_blk_aops ino:800002
> [  898.286191] flags: 0x17ffffc0002022(referenced|active|private|node=0|zone=2|lastcpupid=0x1fffff)
> [  898.286193] raw: 0017ffffc0002022 ffffb3618ba03ba8 ffffb3618ba03ba8 ffff947287522ab0
> [  898.286195] raw: 0000000000c00066 ffff947281729340 00000003ffffffff ffff947290991000
> [  898.286196] page dumped because: migration failure
> ...
> 
> At this point, two things can happen:
> 
> a) the constant flow of printk() slows down the VM to the point a timeout
> triggers (either autotest timeout or kernel selftests timeout, it doesn't
> matter), terminates memory-hotplug and the VM resume processing the remaning
> ubuntu_kernel_selftests jobs
> 
> or
> 
> b) the filesystem fills up to 100%, memory-hotplug fails, but so does every
> remaining test jobs since the VM is in an unusable state at this point

Why the filesystem fills up? Journald should have strict limits for its
logs... unless we keep logging it to a file and ignore any journald
MaxUse/KeepFree?

> 
> Given we already disable memory-hotplug for arm* and cloud kernels, and to avoid
> having our tests session be trashed by this single test, i propose to disable it
> entirely, or at least until a ratelimit solution is put in place.

I would prefer to keep memory hotplug. It's a quite nice test for memory
reclaim, migration and compaction. It should really stress the mm.

> 
> If you want to reproduce this issue, just provision an openstack instance
> (small, medium or large - size doesn't matter) and you will always endup in
> scenario "b".
> 
> Signed-off-by: Paolo Pisati <paolo.pisati at canonical.com>
> ---
>  ubuntu_kernel_selftests/control | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/ubuntu_kernel_selftests/control b/ubuntu_kernel_selftests/control
> index e2874196..53c5584a 100644
> --- a/ubuntu_kernel_selftests/control
> +++ b/ubuntu_kernel_selftests/control
> @@ -12,7 +12,7 @@ DOC = ""
>  
>  name = 'ubuntu_kernel_selftests'
>  
> -tests = [ 'setup','breakpoints','cpu-hotplug','efivarfs','memfd','memory-hotplug','mount','net','ptrace','seccomp','timers','powerpc','user','ftrace' ]
> +tests = [ 'setup','breakpoints','cpu-hotplug','efivarfs','memfd','mount','net','ptrace','seccomp','timers','powerpc','user','ftrace' ]
>  
>  #
>  #  The seccomp tests on 4.19+ on non-x86 are known to be fail and
> 


Best regards,
Krzysztof