| Posted | Nick | Remark | |
|---|---|---|---|
| #openstack-nova - 2018-01-18 | |||
| 09:44:16 | kashyap | (I still need to fix 9 or so unit tests.) | |
| 09:44:23 | mdbooth | kashyap: Looking at that, too | |
| 09:46:12 | mdbooth | kashyap: Whoa, just cranking up my brain to process the commit message :) | |
| 09:46:13 | kashyap | mdbooth: Thank you. I am not sure if I got all the LibvirtConfigGuestCPUFeature() object generation stuff right | |
| 09:46:23 | kashyap | mdbooth: Hehe, that's why I gave the tl;dr :P | |
| 09:46:30 | kashyap | Is it obscenely verbose? | |
| 09:47:03 | mdbooth | No, it's probably just right. | |
| 09:48:23 | kashyap | Gerrit lacks "cover letter" concept. That actually should go into that (although it won't be in the commit message, though) | |
| 09:49:05 | kashyap | mdbooth: The most practical bits are tl;dr and the "Other use cases" -- as in, what else I can use this for | |
| 09:49:36 | kashyap | (s/I/one/) | |
| 09:50:15 | mdbooth | kashyap: Personally I think this is appropriate detail for a commit message. A cover letter is more for navigating multiple commits imho. | |
| 09:50:50 | mdbooth | You can't find a cover letter when git spelunking, so you shouldn't leave critical information there. | |
| 09:51:47 | Spazmotic | I hope john takes mercy on my poor xenapi code today.. I will build an alter of sorts to his xenapis knowledge to assist.+ | |
| 09:53:01 | kashyap | mdbooth: Yeah, you're right. I mixed it up | |
| 09:53:37 | kashyap | mdbooth: Still a bit shaken from my bike ride, where the 140 KM/hr wind gust almost pushed me into the tram! | |
| 09:54:26 | mdbooth | Sounds like an excellent excuse not to be on your bike! | |
| 09:54:28 | kashyap | But point for navigating multiple messages via a cover letter is still a missing feature of Gerrit | |
| 09:55:31 | kashyap | mdbooth: Yeah. I couldn't believe for a moment that the wind was simply "pushing" me aside, like a leaf, and I had to really resist it | |
| 09:55:57 | mdbooth | kashyap: This is where I ride my bike on windy days: https://photos.app.goo.gl/OCo5xBNqWi0yNs5y1 | |
| 09:56:00 | Spazmotic | You need more spoilers and wings on that thing | |
| 09:57:14 | kashyap | mdbooth: Hehe | |
| 09:57:19 | kashyap | I love the bike | |
| 09:57:21 | mdbooth | Cold is fine, wet is... sometimes ok. Ice and wind are never ok. | |
| 09:57:27 | kashyap | Aside: http://knmi.nl/waarschuwingen (About the weather alarm; use translate) | |
| 10:11:19 | mdbooth | kashyap: So I just finished reading and digesting your commit message, and the linked article | |
| 10:12:34 | mdbooth | kashyap: FWIW, assuming libvirt/qemu aren't planning on handling this at that layer, we should probably switch this on *by default* in Nova, with a tuning knob to switch it back off if somebody has a weird reason to need that. | |
| 10:14:21 | kashyap | mdbooth: So you raise a good point | |
| 10:15:04 | mdbooth | kashyap: That wouldn't be a something for this change, though | |
| 10:15:04 | kashyap | mdbooth: About being handled at QEMU level. I was involved on the qemu-devel list thread where there was a debate about adding a specific CPU model | |
| 10:15:16 | kashyap | That will include the PCID feature by *default* | |
| 10:15:34 | kashyap | However. It's soon getting ridiculous, because of this exhibit: | |
| 10:16:03 | kashyap | E.g. one CPU model name will be: 'Haswell-noTSX-IBRS' | |
| 10:16:08 | kashyap | See anything odd? | |
| 10:16:23 | kashyap | How about this: 'Haswell-noTSX-IBRS-nowThisBug-andAlsoThusBug-AndMoreBugs' | |
| 10:16:33 | mdbooth | Yeah, that's pretty silly | |
| 10:17:14 | kashyap | So that was the thread, please read DanPB's response on context of Nova: https://lists.nongnu.org/archive/html/qemu-devel/2018-01/msg03689.html | |
| 10:17:24 | kashyap | mdbooth: Thanks for taking time to read this! I appreciate the concentration | |
| 10:17:52 | kashyap | 'this' as in: the Nova change and all the related info | |
| 10:18:18 | kashyap | mdbooth: But the thing is...about switching on by _default_, it's complicated. | |
| 10:18:23 | mdbooth | From reading that post, it sounds like this is something (?:pretty much)? all our users will want. | |
| 10:18:47 | kashyap | As this perf impact will only occur when someone chooses one of the named CPU models that doesn't have the PCID feature in libvirt's notion of the model. | |
| 10:18:52 | kashyap | (But, it exists in the hardware) | |
| 10:18:59 | kashyap | mdbooth: It won't affect users | |
| 10:19:06 | kashyap | ...*if* they chose 'host-model' | |
| 10:19:12 | mdbooth | users==operators | |
| 10:19:16 | kashyap | In that case, libvirt will do the grump work for you | |
| 10:19:23 | kashyap | mdbooth: (Yeah, I translated as much) | |
| 10:19:29 | kashyap | s/grump/grunt/ | |
| 10:20:27 | kashyap | mdbooth: One thing is for *sure*. We (or I) have to do some clear write-up about what is the operator impact in all three cases: | |
| 10:20:31 | kashyap | (1) 'host-model' | |
| 10:20:35 | kashyap | (2) 'host-passthrough' | |
| 10:20:51 | mdbooth | kashyap: Is that something we can detect at startup? Host-model = X, real cpu is Y, so we should change host-model to X + PCID | |
| 10:20:51 | kashyap | (3) Custom CPU model <-- this is where my change comes in | |
| 10:22:30 | mdbooth | A reason *not* to do this would be the upgrade impact of not being able to live-migrate across the boundary? | |
| 10:22:45 | mdbooth | i.e. X != X+PCID, so you can't live migrate | |
| 10:23:04 | Spazmotic | You mean for the CPU mismatch? | |
| 10:23:04 | kashyap | mdbooth: Yes, live migration is a strict requirement | |
| 10:23:08 | mdbooth | Yeah | |
| 10:23:10 | kashyap | Yes, mismatch, indeed | |
| 10:23:13 | mdbooth | Spazmotic: Yeah | |
| 10:23:31 | kashyap | mdbooth: I still need to think more clearly about detecting it at guest start-up, where Nova generates the guest XML | |
| 10:23:41 | mdbooth | So if we could maintain host model strictly across live migrate, but reset it on restart... | |
| 10:23:41 | kashyap | What you're saying is --- | |
| 10:24:00 | mdbooth | s/guest/host/ startup | |
| 10:24:01 | kashyap | "If the guest is using a CPU without the PCID feature, add it." | |
| 10:24:22 | kashyap | (Assuming we detect that cleanly.) | |
| 10:26:32 | kashyap | mdbooth: So, from #virt, OFTC: | |
| 10:26:33 | kashyap | 11:21 < kashyap> Hi folks, can we detect at boot / start-up time what CPU model a guest is using? | |
| 10:26:36 | kashyap | 11:22 < kashyap> E.g. 'host-model' / 'host-passthrough' / or some custom model | |
| 10:26:39 | kashyap | 11:25 < danpb> in general you can't | |
| 10:26:41 | kashyap | 11:25 < danpb> you just get to see a model + flags in /proc/cpuinfo | |
| 10:27:58 | mdbooth | kashyap: I don't understand why we're interested in what the guest sees | |
| 10:28:17 | mdbooth | I mean, the guest is interested in what the guest sees, but we're just interested in what we present | |
| 10:28:36 | mdbooth | And we can absolutely determine that | |
| 10:30:11 | kashyap | mdbooth: Err, you're right. We should detect before the start-up | |
| 10:30:49 | mdbooth | kashyap: My thinking was that the host configuration for how guests are started is static, so we'd do it at host startup. | |
| 10:30:51 | kashyap | Using the baselineCPU() API | |
| 10:30:58 | kashyap | And VIR_CONNECT_BASELINE_CPU_EXPAND_FEATURES. | |
| 10:31:56 | mdbooth | Does that require a running domain? Or does it just query the xml file you referenced? | |
| 10:34:17 | kashyap | No, not a running domain | |
| 10:35:29 | kashyap | mdbooth: Near as I recall, libvirt caches the capabilities info it got from QEMU, via a QMP command. | |
| 10:35:48 | kashyap | (Before guest start up, obviously) | |
| 10:35:55 | kashyap | We'd be querying that cached XML, IIUC. | |
| 10:38:16 | Spazmotic | Checking my Xen boxes out of curiousity now | |
| 10:39:32 | kashyap | mdbooth: I'll stop hand-waving here, and get back with clearer details on the review. | |
| 10:39:39 | openstackgerrit | Stephen Finucane proposed openstack/nova master: Fix openstackdocstheme options for api-ref https://review.openstack.org/534712 | |
| 10:39:39 | openstackgerrit | Stephen Finucane proposed openstack/nova master: trivial: Remove crud from 'conf.py' https://review.openstack.org/534713 | |
| 10:40:55 | Spazmotic | Yeah interesting... i may need to send out an email to some peoples heh | |
| 10:41:47 | bauzas | gentle reminder for gibi and stephenfin about https://review.openstack.org/#/c/528832/ ;) | |
| 10:41:51 | lyarwood | kashyap: before you go, have you seen `Live Migration failure: invalid argument: monitor must not be NULL: libvirtError: invalid argument: monitor must not be NULL | |
| 10:42:05 | lyarwood | kashyap: urgh sorry, paste fail, ^ LM failure on f26 with the virt-preview repo | |
| 10:43:03 | kashyap | lyarwood: Got a link? | |
| 10:43:12 | lyarwood | ah wait that isn't the virt-preview repo | |
| 10:43:19 | lyarwood | kashyap: nope sorry local failure at the moment | |
| 10:44:29 | kashyap | Phew, okay. One less live migration issue to worry about, then | |
| 10:46:41 | lyarwood | cool, virt-preview works anyway | |
| 10:46:43 | lyarwood | sorry about that | |
| 10:51:30 | kashyap | No problem | |
| 11:02:37 | ameeda | jaypipes: good morning :) what If I use glance API to check the instance_metadata from nova side ? where is the wrong in that ? | |
| 11:04:27 | ameeda | jaypipes: I think that glance store image properties to nova db table "instance_metadata" | |