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From li jerry <>
Subject 回复: KVM host AvailableMemory data is incorrect
Date Tue, 21 Jul 2020 07:04:36 GMT
@Andrija Panic<> Sorry, there are other VMs running on
this HOST, and they have allocated 160G of memory in total.
What I want to express is that we should mark Buffers as AvailableMemory

Because Buffers memory can be automatically recycled by the system


发件人: Andrija Panic<>
发送时间: 2020年7月21日 14:48
收件人: users<>; li jerry<>
主题: Re: KVM host AvailableMemory data is incorrect

@li jerry<> if ACS tells you your KVM host has 16GB instead
256GB - that is wrong by all means - and you should try to see where this comes from (have
you upgraded the host in the meantime, or did anything with it) ?
Even with your break-down of total/cache/buffers etc - your host *should* has more than 100GB
free (buffers + cache = 92GB out of 256B)

You should check you "slab" usage etc - there are other "hiden" RAM usage beside the buffer
and cache.


On Thu, 16 Jul 2020 at 17:24, Riepl, Gregor (SWISS TXT) <<>>
Sounds like a calculation bug in cloudstack-agent then.
You should probably report it on Github.
From: li jerry <<>>
Sent: 15 July 2020 12:08
To:<> <<>>
Subject: 回复: KVM host AvailableMemory data is incorrect

In my scene

KVM host
cat /proc/meminfo

When I want to deploy a VM with 32G memory to this host, it prompts that the resources are
insufficient (mem.overprovisioning.factor=1.0).

CLOUDSTACK tells me that KVMHOST has 16GB of available memory (it does not count Buffers).
So 16<32, so there is not enough data.

But I manually started a VM with 32G memory on KVM HOST, and it succeeded; and Buffers/cached/memfree/they
were reduced accordingly.

Can we add the memory occupied by Buffers to AvailableMemory and report to CLOUDSTACK?

发件人: Riepl, Gregor (SWISS TXT) <<>>
发送时间: 2020年7月15日 17:41
主题: Re: KVM host AvailableMemory data is incorrect

This sounds very familiar...
and they rolled it back in
because upstream didn't accept their patch.

We had to "fix" our memory monitoring twice because of this.

It's important to *not* calculate buffer/cache memory towards memory usage, because the kernel
can reclaim this memory whenever there is a need.
From: li jerry <<>>
Sent: 15 July 2020 08:27
To:<> <<>>
Subject: KVM host AvailableMemory data is incorrect

Hello everyone
     We use HCI to run CloudStack (KVM+CEPH). After running for a period of time, cloudstack
reports that HOST has no available memory. But ZABBIX monitoring shows that HOST still has
a lot of available memory. By observing /proc/meminfo on KVM HOST, it is found that most of
the memory is occupied by Buffers.

     Further analysis of the source code of cloudstack-agent shows that the algorithm for
cloudstack-agent to obtain AvailableMemory on the host is:

Cached +MemFree -reservedMemory +overCommitMemory

It does not calculate the memory occupied by Buffers.

Excuse me, can I mark the memory occupied by Buffers as AvailableMemory?

If not, what is the reason?

Thank you!

-       Jerry


Andrija Panić

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