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From Wido den Hollander <w...@widodh.nl>
Subject Re: KVM Host overprovisioning
Date Tue, 12 Sep 2017 06:46:10 GMT

> Op 11 september 2017 om 13:04 schreef Ivan Kudryavtsev <kudryavtsev_ia@bw-sw.com>:
> 
> 
> Hi, Wido.
> 
> Yes, you can. But it works not the way I expect because It cuts RAM from VM
> by dividing it to overprovisioning factor like VM with 2GB of RAM with
> Overprovisioning factor 2.0 will get 1GB displayed with "free" command.
> That's why I finished the message with words that it might be I just don't
> get the idea. The behaviour is the same in my prod 4.3 and new 4.9.
> 

Hmm, ok.

So for the KVM Agent you can add "host reserved mb" to the agent.properties, but you are proposing
a setting where you can multiply the memory?

Eg by 1.5 if you want to and have the Agent expose that to the MGMT server?

Wido

> 2017-09-11 18:00 GMT+07:00 Wido den Hollander <wido@widodh.nl>:
> 
> > Hi,
> >
> > > Op 10 september 2017 om 8:37 schreef Ivan Kudryavtsev <
> > kudryavtsev_ia@bw-sw.com>:
> > >
> > >
> > > Hello, community.
> > >
> > > During the last years Linux kernel got some interesting features like
> > KSM,
> > > ZSWAP, ZRAM. Hardware also steps forward and we see Intel 3d xpoint,
> > > extremely fast SSD drives with m.2 and PCI-E interfaces.
> > >
> > > These facilities enable potentially interesting use of overcommited RAM
> > for
> > > hosts. According to IBM's investigations Zswap with LZ4/ZBUD increases
> > > virtual RAM on 40%.
> > >
> > > I investigated current Apache CloudStack memory overcommitment
> > capabilities
> > > and they mostly affect VM's RAM by utilizing ballooning and I think it's
> > > not what necessary to open new facilities. There are many cases which can
> > > utilize ZSWAP and fast swap devices to efficiently provision more RAM
> > than
> > > presents.
> > >
> > > I suppose, CloudStack Agent for KVM can have configured parameter which
> > > "mangles" RAM reported. From the other hand it can be done by implemented
> > > host properties on server side. I tried manual increasing in host table:
> > >
> > > update host set ram=ram * 1.4 where id=1;
> > >
> > > and it seems until the next host stats update it works as expected. I
> > think
> > > this workaround is useful, but it's better to have the function in core
> > > like standard.
> > >
> >
> > Can't you set memory over provisioning on a cluster basis in the GUI? I
> > thought you could.
> >
> > Wido
> >
> > > Let me know what you think about it, it might be I don't understand
> > > something and ACS already has it in place? I also would like to hear your
> > > thoughts on ZSWAP usage in practice.
> > >
> > > --
> > > With best regards, Ivan Kudryavtsev
> > > Bitworks Software, Ltd.
> > > Cell: +7-923-414-1515
> > > WWW: http://bitworks.software/ <http://bw-sw.com/>
> >
> 
> 
> 
> -- 
> With best regards, Ivan Kudryavtsev
> Bitworks Software, Ltd.
> Cell: +7-923-414-1515
> WWW: http://bitworks.software/ <http://bw-sw.com/>

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