8:06 p.m.
Hello folks.
On simple libvirt/KVM hosts in order to improve RAM usage and avoid swap
to disk I use zRam with swap to RAM technique. So create half of amount
of host memory in zRam disk divided by the number of CPU cores. Works
pretty well.
Has anyone tried it with oVirt Nodes or even has it been considered as a
feature to simply turn on/off ?
Thanks
Fernando
9:41 p.m.
On Dec 30, 2016 7:06 PM, "Fernando Frediani"
<fernando.frediani(a)upx.com.br>
wrote:
Hello folks.
On simple libvirt/KVM hosts in order to improve RAM usage and avoid swap to
disk I use zRam with swap to RAM technique. So create half of amount of
host memory in zRam disk divided by the number of CPU cores. Works pretty
well.
Has anyone tried it with oVirt Nodes or even has it been considered as a
feature to simply turn on/off ?
What exactly is the use case?
I'd use zram for temporary disks, using the VDSM hook for them.
I think you are referring to zswap?
Y.
Thanks
Fernando
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10:12 p.m.
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Hello it's the same thing zswap.
The use case is to be able to put more stuff in a single host without it
need needing to swap to slow disks. You sacrifice CPU and avoid a lot
slower swap to disk.
Fernando
On 30/12/2016 16:41, Yaniv Kaul wrote:
On Dec 30, 2016 7:06 PM, "Fernando Frediani"
<fernando.frediani(a)upx.com.br <mailto:fernando.frediani@upx.com.br>>
wrote:
Hello folks.
On simple libvirt/KVM hosts in order to improve RAM usage and
avoid swap to disk I use zRam with swap to RAM technique. So
create half of amount of host memory in zRam disk divided by the
number of CPU cores. Works pretty well.
Has anyone tried it with oVirt Nodes or even has it been
considered as a feature to simply turn on/off ?
What exactly is the use case?
I'd use zram for temporary disks, using the VDSM hook for them.
I think you are referring to zswap?
Y.
Thanks
Fernando
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Users mailing list
Users(a)ovirt.org <mailto:Users@ovirt.org>
http://lists.ovirt.org/mailman/listinfo/users
<http://lists.ovirt.org/mailman/listinfo/users>
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<p>Hello it's the same thing zswap.</p>
<p>The use case is to be able to put more stuff in a single host
without it need needing to swap to slow disks. You sacrifice CPU
and avoid a lot slower swap to disk.</p>
<p>Fernando</p>
<div class="moz-cite-prefix">On 30/12/2016 16:41, Yaniv Kaul
wrote:<br>
</div>
<blockquote
cite="mid:CAJgorsaLkPqhrNvK7ttWx2EwpJ_pzQh3T6KW4AsXF7GPNj3jqg@mail.gmail.com"
type="cite">
<div dir="auto">
<div><br>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Dec 30, 2016 7:06 PM,
"Fernando
Frediani" <<a moz-do-not-send="true"
href="mailto:fernando.frediani@upx.com.br">fernando.frediani@upx.com.br</a>>
wrote:<br type="attribution">
<blockquote class="quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">Hello
folks.<br>
<br>
On simple libvirt/KVM hosts in order to improve RAM
usage and avoid swap to disk I use zRam with swap to RAM
technique. So create half of amount of host memory in
zRam disk divided by the number of CPU cores. Works
pretty well.<br>
<br>
Has anyone tried it with oVirt Nodes or even has it been
considered as a feature to simply turn on/off ?<br>
</blockquote>
</div>
</div>
</div>
<div dir="auto"><br>
</div>
<div dir="auto">What exactly is the use case? </div>
<div dir="auto">I'd use zram for temporary disks, using the
VDSM
hook for them. </div>
<div dir="auto">I think you are referring to zswap? </div>
<div dir="auto">Y. </div>
<div dir="auto">
<div class="gmail_extra">
<div class="gmail_quote">
<blockquote class="quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
Thanks<br>
Fernando<br>
<br>
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target="_blank">Users(a)ovirt.org</a><br>
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href="http://lists.ovirt.org/mailman/listinfo/users"
rel="noreferrer"
target="_blank">http://lists.ovirt.org/mailman<wbr>/li...
</blockquote>
</div>
<br>
</div>
</div>
</div>
</blockquote>
<br>
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2:47 a.m.
I enable zSwap on my oVirt nodes by default. However zSwap is not the same thing as zRam.
The purpose of zSwap is decreasing I/O by compressing swap itself. zSwap uses some ram for
compressed swap, but it doesn’t try to keep a page in memory if it can’t be compressed.
I find using of zRam without swap too risky. You don’t know when OOM killer start its
job.
-----Original Message-----
From: <users-bounces(a)ovirt.org> on behalf of Fernando Frediani
<fernando.frediani(a)upx.com.br>
Date: Friday 30 December 2016 at 20:06
To: "users(a)ovirt.org" <users(a)ovirt.org>
Subject: [ovirt-users] Using zRam with oVirt Nodes
Hello folks.
On simple libvirt/KVM hosts in order to improve RAM usage and avoid swap
to disk I use zRam with swap to RAM technique. So create half of amount
of host memory in zRam disk divided by the number of CPU cores. Works
pretty well.
Has anyone tried it with oVirt Nodes or even has it been considered as a
feature to simply turn on/off ?
Thanks
Fernando
_______________________________________________
Users mailing list
Users(a)ovirt.org
http://lists.ovirt.org/mailman/listinfo/users
3:01 p.m.
All nodes I user zSwap (or Swap in zRam) I do have also some swap space
in disk with lower priority which when/if gets used means something warning.
Overall the usage of zSwap helps a lot to increase the density of a Host
at the cost of CPU which in most cases is more idle than memory or storage
Fernando
On 30/12/2016 21:47, Pavel Gashev wrote:
I enable zSwap on my oVirt nodes by default. However zSwap is not the
same thing as zRam. The purpose of zSwap is decreasing I/O by compressing swap itself.
zSwap uses some ram for compressed swap, but it doesn’t try to keep a page in memory if it
can’t be compressed.
I find using of zRam without swap too risky. You don’t know when OOM killer start its
job.
-----Original Message-----
From: <users-bounces(a)ovirt.org> on behalf of Fernando Frediani
<fernando.frediani(a)upx.com.br>
Date: Friday 30 December 2016 at 20:06
To: "users(a)ovirt.org" <users(a)ovirt.org>
Subject: [ovirt-users] Using zRam with oVirt Nodes
Hello folks.
On simple libvirt/KVM hosts in order to improve RAM usage and avoid swap
to disk I use zRam with swap to RAM technique. So create half of amount
of host memory in zRam disk divided by the number of CPU cores. Works
pretty well.
Has anyone tried it with oVirt Nodes or even has it been considered as a
feature to simply turn on/off ?
Thanks
Fernando
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4 comments
3 participants
participants (3)
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Fernando Frediani -
Pavel Gashev -
Yaniv Kaul