Re: [Xen-devel] arm: xl vcpu-pin leads to oom-killer slashing processes

[Andrii Anisov <andrii.anisov@xxxxxxxxx>]

On 05.12.18 15:13, Julien Grall wrote:
> I need at least some sort of proof that Xen might corrupt the kernel. I don't 
> believe we manage to just corrupt the kernel memory subsystem with good enough 
> value reliably. So maybe we should start looking at more plausible cause.
I think I would be able to look deeper into it by the end of the week.

> It does not mean this is because of Xen. It might just be because of Xen 
> drivers that does not free memory.
Totally agree. I did not dig into it yet. Just made a notification, so maybe 
other interested parties can check/verify the issue on different setups.

> I tried and can't reproduce it.
Great. So it might be the problem on my setup.

> But I am using 4.20-rc4 and not 4.14.35. If you think the bug was introduced in 
> recent Xen, then the first step is to downgrade Xen. If it does not happen on 
> the downgraded version, then you can bisect it.
It definitely does not reproduce with XEN 4.10 release. But it is pretty old.

> How about after vCPU pining? Do you see the memory free going down?
I've checked, and seen a strange thing: memtotal is shrinked down.
Meminfo before vcpu pin:

MemTotal:        2995828 kB
MemFree:         2810360 kB
MemAvailable:    2758420 kB
Buffers:               0 kB
Cached:            53092 kB
SwapCached:            0 kB
Active:            26716 kB
Inactive:          40980 kB
Active(anon):      14976 kB
Inactive(anon):    20648 kB
Active(file):      11740 kB
Inactive(file):    20332 kB
Unevictable:          12 kB
Mlocked:              12 kB
SwapTotal:             0 kB
SwapFree:              0 kB
Dirty:                 0 kB
Writeback:             0 kB
AnonPages:         14644 kB
Mapped:            31632 kB
Shmem:             21020 kB
Slab:              29204 kB
SReclaimable:       9924 kB
SUnreclaim:        19280 kB
KernelStack:        2848 kB
PageTables:          828 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     1497912 kB
Committed_AS:      58556 kB
VmallocTotal:   135290290112 kB
VmallocUsed:           0 kB
VmallocChunk:          0 kB
AnonHugePages:         0 kB
ShmemHugePages:        0 kB
ShmemPmdMapped:        0 kB
CmaTotal:         393216 kB
CmaFree:          360488 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB


Meminfo before oom-killer rose:

root@salvator-x:~# cat /proc/meminfo
MemTotal:         549000 kB
MemFree:          412108 kB
MemAvailable:     347472 kB
Buffers:               0 kB
Cached:            19356 kB
SwapCached:            0 kB
Active:            15920 kB
Inactive:          17512 kB
Active(anon):      14516 kB
Inactive(anon):     9104 kB
Active(file):       1404 kB
Inactive(file):     8408 kB
Unevictable:          12 kB
Mlocked:              12 kB
SwapTotal:             0 kB
SwapFree:              0 kB
Dirty:                 0 kB
Writeback:             0 kB
AnonPages:         14160 kB
Mapped:             9016 kB
Shmem:              9496 kB
Slab:              26412 kB
SReclaimable:       6792 kB
SUnreclaim:        19620 kB
KernelStack:        2880 kB
PageTables:          776 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:      274500 kB
Committed_AS:      49264 kB
VmallocTotal:   135290290112 kB
VmallocUsed:           0 kB
VmallocChunk:          0 kB
AnonHugePages:         0 kB
ShmemHugePages:        0 kB
ShmemPmdMapped:        0 kB
CmaTotal:         393216 kB
CmaFree:          360488 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB


> So that's reliably happening?
It is 100% reproducible on my setup.

> Are you sure there are nothing else on the system using memory? For instance 
> you seem to have nfs in place.
Yes, Dom0 root is nfs.

--
Sincerely,
Andrii Anisov.

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