[PATCH 1/1] manpages/virsh.rst: clarify numatune memory migration on Linux

Daniel Henrique Barboza danielhb413 at gmail.com
Tue Jun 16 13:32:38 UTC 2020

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 at 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 ....



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