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From li jerry <>
Subject 回复: KVM host AvailableMemory data is incorrect
Date Wed, 15 Jul 2020 10:08:00 GMT
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
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