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From Ivan Kudryavtsev <kudryavtsev...@bw-sw.com>
Subject Re: KVM Host overprovisioning
Date Mon, 11 Sep 2017 11:04:12 GMT
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.

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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