* hugetlbfs and KSM
@ 2010-04-08 19:29 Bernhard Schmidt
2010-04-09 20:03 ` Chris Wright
0 siblings, 1 reply; 3+ messages in thread
From: Bernhard Schmidt @ 2010-04-08 19:29 UTC (permalink / raw)
To: kvm
Hi,
running Debian Squeeze with a 2.6.32-3-amd64 kernel and qemu-kvm 0.12.3
I enabled hugetlbfs on a rather small box with about five similar VMs
today (all Debian Squeeze amd64, but different services)
Pro:
* system load on the host has gone way down (by about 50%)
Contra:
* KSM seems to be largely ineffective (100MB saved -> 1.3MB saved)
Am I doing something wrong? Is this a bug? Is this generally impossible
with large pages (which might explain the lower load on the host, if
large pages are not scanned)? Or is it just way less likely to have
identical pages at that size?
Bernhard
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: hugetlbfs and KSM
2010-04-08 19:29 hugetlbfs and KSM Bernhard Schmidt
@ 2010-04-09 20:03 ` Chris Wright
0 siblings, 0 replies; 3+ messages in thread
From: Chris Wright @ 2010-04-09 20:03 UTC (permalink / raw)
To: Bernhard Schmidt; +Cc: kvm
* Bernhard Schmidt (berni@birkenwald.de) wrote:
> * KSM seems to be largely ineffective (100MB saved -> 1.3MB saved)
>
> Am I doing something wrong? Is this a bug? Is this generally impossible
> with large pages (which might explain the lower load on the host, if
> large pages are not scanned)? Or is it just way less likely to have
> identical pages at that size?
KSM only scans and merges 4k pages.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: hugetlbfs and KSM
[not found] <579435996.2170.1270755367936.JavaMail.root@mail1.martinsales.net>
@ 2010-04-08 19:36 ` David Martin
0 siblings, 0 replies; 3+ messages in thread
From: David Martin @ 2010-04-08 19:36 UTC (permalink / raw)
To: kvm; +Cc: berni
I asked this question quite a while ago, it seems huge pages do not get scanned for merging.
David Martin
----- "Bernhard Schmidt" <berni@birkenwald.de> wrote:
> Hi,
>
> running Debian Squeeze with a 2.6.32-3-amd64 kernel and qemu-kvm
> 0.12.3
> I enabled hugetlbfs on a rather small box with about five similar VMs
> today (all Debian Squeeze amd64, but different services)
>
> Pro:
> * system load on the host has gone way down (by about 50%)
>
> Contra:
> * KSM seems to be largely ineffective (100MB saved -> 1.3MB saved)
>
> Am I doing something wrong? Is this a bug? Is this generally
> impossible
> with large pages (which might explain the lower load on the host, if
> large pages are not scanned)? Or is it just way less likely to have
> identical pages at that size?
>
> Bernhard
>
> --
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^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2010-04-09 20:03 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2010-04-08 19:29 hugetlbfs and KSM Bernhard Schmidt
2010-04-09 20:03 ` Chris Wright
[not found] <579435996.2170.1270755367936.JavaMail.root@mail1.martinsales.net>
2010-04-08 19:36 ` David Martin
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