QEMU balloon script abstraction improvement #248
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The balloon command of qemu expects the total guest size. Alter the qemu balloon script to calculate the correct value from passed balloon size to make functionality closer to that with other hypervisors. Signed-off-by: Santtu Lakkala <[email protected]>
Use query-balloon command instead of relying on the changed signal for slightly improved reliability. The 2 second delay between commands is arbitrarily chosen. Signed-off-by: Santtu Lakkala <[email protected]>
lib/runners/qemu.nix
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| ${writeQmp { execute = "balloon"; arguments.value = 987; }} | ||
| ) | sed -e s/987/$VALUE/ | \ | ||
| (${writeQmp { execute = "balloon"; arguments.value = 987; }}) | sed -e s/987/$VALUE/ | ||
| ${pkgs.coreutils}/bin/sleep 2 |
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The other VMMs also exhibit delayed effects. I think we should add the sleep to the other runners, too.
Also, the hardcoded 2 might be too low for loaded systems. Do you mind creating an option for it?
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Cloud-hypervisor didn't seem to require a delay, added delay to crosvm and made the delay configurable (still defaults to 2)
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I am happy with this. Thanks!
One last question before merging: do you really think it's intuitive to pass the amount of Megabytes to remove from the memory size? Personally, I would expect the number to be the size of the balloon memory available to the VM. Then again I don't use ballooning myself, so your opinion is all that matters to me.
Make the QEMU balloon script abstract away the difference between hypervisor balloon commands. The QMP balloon command expects the wanted memory size of the guest, so calculate the correct value from the balloon size given as argument.
Also some changes to reported balloon size; the changed signal is not emitted, if balloon size is not changed; and may report an old value.