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#openstack-nova - 2020-03-13
16:31:09 kashyap sean-k-mooney: No, no you're mixing up CPU model and machine type for AArch64
16:31:20 kashyap sean-k-mooney: 'virt' is still the recommended machine type for AArch64.
16:31:32 kashyap melwitt: Yeap.
16:31:33 sean-k-mooney ah yes i am
16:31:45 melwitt cool
16:31:54 sean-k-mooney this still will cause issue for live migration if we use max
16:32:08 sean-k-mooney so i dont know if that is a good default
16:32:13 kashyap melwitt: I _think_ first want to care about TCG, because for KVM, you'd need AArch64 hardware in the CI
16:32:25 kashyap sean-k-mooney: I've talked to the AArch64 maintainer, I'm posting the recommendations in the patch.
16:32:31 sean-k-mooney kashyap: we have AArch64 hardware in ci
16:32:33 melwitt kashyap: ack
16:32:46 sean-k-mooney kashyap: thats the whole point lenario donated some
16:32:49 kashyap sean-k-mooney: Good, then. We've got the recommendations for that, too.
16:32:56 melwitt kashyap: so do you think TCG would be a separate column in the matrix?
16:32:58 kashyap Linaro, I take it. Yeah
16:33:05 kashyap melwitt: Yeah, I'd say so.
16:33:08 sean-k-mooney ah yes
16:33:14 melwitt ok. thanks for explaining all this
16:33:16 kashyap (We need to clearly distinguish both cases.)
16:33:25 kashyap No worries, I need to refresh this every few months mysel f:D
16:33:34 melwitt :)
16:33:53 sean-k-mooney kashyap: we proably should be using the cpu_mode config option to define this
16:34:30 sean-k-mooney e.g. tie it in to host-passthough and host-model some how
16:35:37 stephenfin sean-k-mooney: how strongly do you feel about https://review.opendev.org/#/c/468203 ?
16:35:45 stephenfin specifically jaypipes arguments there
16:35:47 kashyap sean-k-mooney: One thing at a time :-)
16:36:00 sean-k-mooney im also not sure how i feel about htis being a bug, it fells more like a specless blueprint but im not going to really object too stronly to it beign a bug
16:37:00 stephenfin I ask because I'm trying to decide how to say "these cores should be dedicated" in a mixed instance
16:37:16 sean-k-mooney kashyap: well for now they could jsut use cpu_mode=custom and cpu_model=max or cpu_model=min right
16:37:35 stephenfin Currently I'm going with 'hw:cpu_dedicated_mask', which is a CPU list
16:37:38 sean-k-mooney stephenfin: am ill take a look now
16:37:48 sean-k-mooney stephenfin: ya i would be fine with that
16:37:55 sean-k-mooney stephenfin: whats the other option
16:38:05 stephenfin there are a few
16:38:34 stephenfin in this scenario that I'm following, you'll be able to use hw:cpu_dedicated_mask *or* hw:cpu_realtime_mask
16:38:59 sean-k-mooney stephenfin: no you would use both
16:39:01 stephenfin I see no reason to say these cores are shared, these are dedicated but non-realtime, and these are dedicated and realtime
16:39:04 sean-k-mooney well optinally
16:39:16 sean-k-mooney e.g. not an exclucive or
16:39:41 sean-k-mooney i dont see a reason to block it
16:39:41 stephenfin why? What real-world user is going to use all three types of core in an instance?
16:39:49 stephenfin Because it's less complicated
16:39:55 sean-k-mooney its more complicated
16:40:20 sean-k-mooney the validation logic to prevent all 3 is extra logic we dont need if we allow it
16:40:45 stephenfin A|B is easier grok than A.issubset(B)
16:40:56 stephenfin and the it makes my XML generation easier
16:41:02 stephenfin s/the //
16:41:04 sean-k-mooney stephenfin: you are over loading hw:cpu_realtime_mask
16:41:18 sean-k-mooney its behavior would change based on the hw:cpu_policy
16:41:29 sean-k-mooney so that gets harder to reason about
16:41:36 stephenfin nope, it stays the same: these are cores that are real-time
16:41:39 sean-k-mooney if we allow both it does not
16:41:41 stephenfin what changes is what happens to the other cores
16:41:53 stephenfin and that's purely based on hw:cpu_policy
16:42:10 sean-k-mooney no it chacnge form tehse are realtime to these are realtime and dedicated and the rest flaot
16:42:17 kashyap sean-k-mooney: Not entirely; there's also a quirk of making sure to specify the interrupt controller (as the default is less featureful) -- `-machine gic-version=max`
16:42:29 kashyap melwitt: For later, added my notes in the change.
16:42:32 stephenfin they're always realtime and dedicated
16:42:39 stephenfin you can't have realtime floating cores
16:42:45 melwitt kashyap: thanks
16:43:05 sean-k-mooney well libvirt allows you to but that is a seperate thign
16:43:14 stephenfin ...in nova
16:43:14 kashyap Yep
16:43:20 sean-k-mooney stephenfin: my perference would be to allow both to be set
16:43:38 stephenfin I could allow it, but I don't want to force it
16:43:46 sean-k-mooney and always require hw:dedicated_cpu_mask for mixed
16:43:58 stephenfin and because I don't want to force it, I'd rather say there's only one way to do this
16:44:14 sean-k-mooney which one do you not want to force
16:44:32 sean-k-mooney the realtime mask or the dedicated mask
16:44:33 stephenfin having to set both hw:cpu_dedicated_mask and hw:cpu_realtime_mask
16:44:46 sean-k-mooney right so i would make the cpu_realtime_mask optional
16:44:50 stephenfin if you want a real-time instance with the non-realtime cores floating
16:44:55 sean-k-mooney and always require the cpu_dedicated_mask
16:45:18 stephenfin but then you have a difference of behavior elsewhere
16:45:28 sean-k-mooney and make it so that if you dont set cpu_realtime_mask but do set hw:cpu_realtime=true then we use the hw:dedciated_cpu_mask
16:45:41 stephenfin now you have to use 'hw:cpu_realtime_mask' when using dedicated
16:45:52 stephenfin but use 'hw:cpu_dedicated_mask' when using mixed
16:46:48 stephenfin anyway, we'll invariably debate this in the patch so back to my original question
16:46:52 sean-k-mooney i think its a much simpler rule to say if you want realtime always use realtime_mask and if you want mixed always use the dedicated_mask
16:47:18 sean-k-mooney if you want both use both and require the realtime mask must be a subset of the dedicated mask
16:47:32 stephenfin if we're doing this, do we want to fix that annoying thing where hw:cpu_realtime_mask has to be preceded by carat?
16:47:43 stephenfin because I don't want to force that 'hw:cpu_dedicated_mask'
16:47:54 stephenfin and it would be nice for them to behave similarly
16:48:05 sean-k-mooney stephenfin: ya i would not mind doing that
16:48:23 sean-k-mooney stephenfin: we said the dedicated mask should follow the rules for the config opntion
16:48:30 sean-k-mooney not the rules for the realtime mask
16:48:33 stephenfin the only reason I see to not do that is jaypipes wanted us to kill 'hw:cpu_realtime_mask' in favor of 'hw:cpu_realtime_set'
16:48:42 stephenfin but tbh, I don't think it's worth the effort
16:48:55 stephenfin we haven't deprecated flavor extra specs before. I don't even want to get into that
16:49:06 sean-k-mooney i would be ok with that i guess but yat that ^
16:49:10 stephenfin ditto for image metadata props, for that matter
16:49:33 stephenfin okay, sweet
16:49:40 stephenfin I can revive those patches so
16:49:43 stephenfin whoo, rebase fun!
16:50:31 sean-k-mooney stephenfin: cool. i prefer each option to do one thing and one thing only. but do what you think is best
16:50:42 sean-k-mooney its a preference not a blocker for me
16:51:10 sean-k-mooney and sice we cant do cross extra spec validation in your validation propsoeal i also prefer that form the avlidation point of view
16:51:36 sean-k-mooney let me know when you want me to review and or play around with it
16:51:47 sean-k-mooney im going to drop soon just an fyi
16:51:47 stephenfin will do

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