09.08.2010 18:27, Daniel Bareiro wrote:
On Monday, 09 August 2010 14:27:12 +0400,
Michael Tokarev wrote:
I have understood that in addition to support from the kernel and
qemu-kvm, there must be support in libc. So in testing I was doing on
Lenny, it did not work using libc from Debian repositories. Now that
squeeze is frozen, anyone knows if it will support KSM?
KSM is working in qemu-kvm packages in bpo, for quite long
time already. It has nothing to do with libc, and now it
does not even require recent-enough kernel headers to compile.
What's needed is recent-enough kernel that actually implements
the feature. The kernel in Lenny does not KSM support, but
the one in bpo has. Also note that Lenny's kernel is too old
for kvm.
I'm using Linux 2.6.32.3 compiled by myself with the kernel.org source
code with support for KSM:
# cat /boot/config-2.6.32.3-dgb | grep KSM
CONFIG_KSM=y
I'm also using qemu-kvm 0.12.1.2 compiled by myself with the source code
of SourceForge.
Note that this one has numerous bugs, some of which involves
data corruption. JFYI.
These are the checks that I was doing in the VMHost:
# ll /sys/kernel/mm/ksm/
total 0
-r--r--r-- 1 root root 4096 ago 9 06:28 full_scans
-rw-r--r-- 1 root root 4096 ago 9 06:28 max_kernel_pages
-r--r--r-- 1 root root 4096 ago 9 06:28 pages_shared
-r--r--r-- 1 root root 4096 ago 9 06:28 pages_sharing
-rw-r--r-- 1 root root 4096 ago 9 06:28 pages_to_scan
-r--r--r-- 1 root root 4096 ago 9 06:28 pages_unshared
-r--r--r-- 1 root root 4096 ago 9 06:28 pages_volatile
-rw-r--r-- 1 root root 4096 ago 9 06:27 run
-rw-r--r-- 1 root root 4096 ago 9 06:28 sleep_millisecs
# cat /sys/kernel/mm/ksm/max_kernel_pages
253500
But KSM seems not work:
# cat /sys/kernel/mm/ksm/pages_sharing
0
Did you actually enable it in the kernel? Did you read
the ksm docs shipped with the kernel?
Should I have some additional consideration when compiling qemu-kvm?
Please note what Nikola Ciprich said. If you don't have
kernel headers that defines MADV_MERGEABLE, you'll have
to define it when compiling kvm.
Note again that debian qemu-kvm package (you're asking
about debian after all) includes support for KSM. It
also includes a small patch to #define that symbol.
/mjt
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