On 14-7-2015 19:16, David Matlack wrote:
(adding back the kvm mailing list)
On Tue, Jul 14, 2015 at 1:12 AM, "C. Bröcker"
<c.brocker@xxxxxxxxxxxxxxxx> wrote:
On 14-7-2015 10:04, Hansa wrote:
On 13-7-2015 20:57, David Matlack wrote:
On Thu, Jun 18, 2015 at 10:26 AM, David Matlack <dmatlack@xxxxxxxxxx>
wrote:
On Thu, Jun 18, 2015 at 1:25 AM, Hansa <forums@xxxxxxxxxx> wrote:
Hi,
I have a LAMP server as guest in KVM. Whenever the server is idle for
some
time it takes about 30 seconds to load a Wordpress site.
If the server is not idle the site shows up in max 5 seconds. I've
already
turned of power management in the guest by passing
GRUB_CMDLINE_LINUX_DEFAULT="apm=off"
in /etc/default/grub. This has no effect.
Does KVM do some power management on guests? If so, how do I turn this
off
for my LAMP guest?
KVM doesn't do any power management of guests. But if everything is idle
on
the host (including your guest), then host power management could kick
in.
Have you tried playing with host pm?
Could you try running your workload with the guest kernel parameter
"idle=poll"
and let me know the performance?
Also, if you are running Linux 4.0 or later on the host, could you try
running
your workload with the KVM module parameter "halt_poll_ns=500000"?
Hansa-- Did you ever get a chance to run your workload with these
changes?
Hi David,
Sorry I didn't respond to your mail earlier and nice of you to check back.
To be honest no I haven't. To much work overload on my side. I've just added
the idle=poll to the guests' grub and rebooted the server. I'll let it run a
few day's to check if it helps. Btw: I'm running 2.6 linux kernel here so
I'm not sure if I can add the "halt_poll_ns" param to KVM.
Best, Hansa
Wow! That makes real difference!
The site was never that fast! Although CPU load is constantly on 100% any
chance I can tweak this param? And is there a similar param for Windows
guests?
Since idle=poll gave a noticeable improvement, your workload is a good
candidate for halt_poll_ns. This is a host KVM module parameter. It will
give you a similar speedup, it will work independent of your guest os,
and won't peg your cpu usage at 100% during periods of no activity. If
you don't have halt_poll_ns available (your host kernel older than 4.0),
is upgrading to a newer kernel or backporting the patch [1] an option?
I'm not sure of any more guest params you can tweak (linux or windows), but
I'll let you know if I come up with anything.
[1] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=f7819512996361280b86259222456fcf15aad926
Sorry David.
That is not an option. It's a production server on 2.6 kernel. 4.0 kernel is not in Base repos and I don't know which impact installing the newer kernel version will have on this server. Any other options?
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