On 6/16/20 9:09 AM, Andrea Bolognani wrote:
On Thu, 2020-06-11 at 14:00 -0300, Daniel Henrique Barboza wrote:
On Linux, changing the nodeset on 'numatune' does not imply that the guest memory will be migrated on the spot to the new nodeset. The memory migration is tied on guest usage of the memory pages, and an idle guest will take longer to have its memory migrated to the new nodeset.
This is a behavior explained in detail in the Linux kernel documentation in Documentation/admin-guide/cgroup-v1/cpusets.rst. The user doesn't need this level of detail though - just needs his/her expectations under check. Running 'numastat' and hoping for instant memory migration from the previous nodeset to the new one is not viable.
There's also parts of the memory that are locked by QEMU in the same place, e.g. when VFIO devices are present. Let's also mention it as another factor that impacts the results the user might expect from NUMA memory migration with numatune.
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com> --- docs/manpages/virsh.rst | 7 +++++++ 1 file changed, 7 insertions(+)
I've tweaked the formatting for the manpage and commit message ever so slightly, added a reference to
https://bugzilla.redhat.com/show_bug.cgi?id=1640869
and pushed. Thanks!
Thanks for the tweaks and pushing. I can't remember now if I totally forgot to add the bug reference or the bug was locked and I couldn't link it. Guess I'll have to double check the other patches waiting for review (TPM proxy, incomplete numa) since they're all tied to RH bugs .... Thanks, DHB