| Posted | Nick | Remark | |
|---|---|---|---|
| #openstack-nova - 2020-04-29 | |||
| 14:00:22 | openstackgerrit | Stephen Finucane proposed openstack/nova master: nova-audit: Use cliff instead of homegrown argparse bleh https://review.opendev.org/724332 | |
| 14:00:30 | artom | I have to say, this shows the power of operator involvement upstream | |
| 14:00:46 | dansmith | artom: man, I really wish this had just been done as migrate-on-load | |
| 14:01:07 | artom | Us devs get "access" to actual large deployment, and the operators get devs not being stupid ;) | |
| 14:01:53 | artom | dansmith, I guess stephenfin's response to that would be "but then we'll never know for sure that we can remove the compat routines" | |
| 14:02:18 | stephenfin | 'zactly | |
| 14:02:30 | dansmith | artom: I think we'd load this whenever we do update available resource, so it'd be migrated within one cycle | |
| 14:02:51 | artom | dansmith, for all instances? | |
| 14:02:54 | dansmith | and if not, we could have just added it to the preloads and forced it to happen | |
| 14:02:56 | gmann | bauzas: gibi oh, i checked locally but i might need to init the policy explicitly depends on when cmd are run. let me test those scenario also. I will do after my internal meeting. | |
| 14:03:00 | dansmith | artom: yes, parallelized by compute node | |
| 14:03:36 | stephenfin | dansmith: have we an in-tree example of this migrate-on-load pattern? | |
| 14:04:02 | dansmith | I can point you at one for sure, but let me see if we have any in current master | |
| 14:04:52 | artom | The fact that belmoreira appears to have RIP'ed running that query is worrisome ;) | |
| 14:06:23 | sean-k-mooney | stephenfin: one thing we could do if this was expensive is to not do it as a normal online data migration in the sense of a global change | |
| 14:06:37 | dansmith | stephenfin: https://github.com/openstack/nova/blob/58aaffade9f78c5fdc6b0d26ec26b70908b7a6aa/nova/objects/migration.py#L89-L89 | |
| 14:06:41 | sean-k-mooney | but instead have a nova manage command that would allow you do it per host | |
| 14:06:52 | dansmith | stephenfin: we generate uuid for migration on load if not present | |
| 14:07:04 | sean-k-mooney | so you could slowly space our the migration host by host until you are done | |
| 14:07:36 | dansmith | sean-k-mooney: we already have batch limits in place, so that doesn't help | |
| 14:07:41 | dansmith | other than create more debt in the form of a new command | |
| 14:07:51 | belmoreira | I was running these in our DBs. Again this is per cell. Some have much more than 1000 instances but for those we don't have numa topology defined. The ones that have numa_topology defined only run batch processing so they are large instances. Meaning that we have x4 or x8 times the number of compute nodes. | |
| 14:08:09 | belmoreira | in both cases queries take few ms | |
| 14:08:21 | sean-k-mooney | well ya that basically what i was thinkign of just limiting the rows it touches but if we can already do that then sure | |
| 14:08:40 | stephenfin | belmoreira++ excellent, thanks for checking that up | |
| 14:08:53 | artom | belmoreira, yep, that's very helpful, thanks! | |
| 14:09:38 | belmoreira | artom stephenfin thanks for ping me on this | |
| 14:09:42 | sean-k-mooney | well there are two parts first the query to get all the instance that need to be migrated then we need to lock the db and update all recoreds | |
| 14:10:01 | sean-k-mooney | you can actully do that in one update query | |
| 14:10:18 | sean-k-mooney | in general bug not in this case | |
| 14:10:24 | artom | belmoreira, just to make sure I understand, you're saying that your numa_topology-having instances are only about 4 to 8 instances per compute host, right? | |
| 14:10:25 | gibi | gmann: ack, thanks | |
| 14:10:25 | dansmith | belmoreira: I'm not sure I got what you said.. you don't have a db with tons of instances with a numa topology to test this on right? | |
| 14:11:49 | sean-k-mooney | if i parsed it correctly the cells with numa instance only run large vms so they have fewer isntances then the other cells | |
| 14:12:01 | dansmith | right | |
| 14:12:01 | belmoreira | artom yes | |
| 14:12:46 | artom | belmoreira, aha, ok - well, it tells us that the sql engine (or sqlalchemy itself?) is smart and checks the more restrictive stuff first - iow having a numa_topology at all | |
| 14:13:03 | artom | But it doesn't tell us what happens if there are thousands of numa_topology-having instances... :( | |
| 14:13:06 | sean-k-mooney | to be fair i would suspect that is likly common of many deployments. e.g. most nuam instance will be large flavors and therefore there will be less of them then standard instances | |
| 14:13:27 | artom | sean-k-mooney, that does seem very likely... | |
| 14:13:47 | dansmith | stephenfin: without the migrate on load, any idea what I can do to tickle those instances to rewrite them? | |
| 14:13:47 | belmoreira | dansmith you're right. I don't have a cell with a lot of instances. <2000 instances only | |
| 14:13:54 | dansmith | belmoreira: gotcha, thanks | |
| 14:14:12 | sean-k-mooney | belmoreira: could you do a count(*) on instance that have a numa topology so we can get a feel for the amount you have | |
| 14:14:32 | belmoreira | sean-k-mooney yes, give a sec | |
| 14:14:53 | sean-k-mooney | just wondering if its in the 100s or roughly what you were messuring | |
| 14:15:53 | sean-k-mooney | artom: i mean we can always fake it if we need too | |
| 14:16:08 | artom | sean-k-mooney, fake what? | |
| 14:16:24 | sean-k-mooney | a db with 1000s of numa instances | |
| 14:16:39 | artom | True | |
| 14:16:49 | belmoreira | our typical use case: | |
| 14:16:52 | belmoreira | select count(*) from instance_extra where deleted = 0; #711 | |
| 14:16:52 | belmoreira | select count(*) from compute_nodes nodes; #176 | |
| 14:16:53 | belmoreira | select * from instance_extra where deleted = 0 and numa_topology is not null and numa_topology like "%nova_object.name%"; #took 38.2 ms | |
| 14:17:10 | sean-k-mooney | ok so 700 ish is not bad | |
| 14:17:27 | sean-k-mooney | its not 2000 but its not 10 | |
| 14:18:07 | artom | So based on those number it might actually be OK to go ahead as is... | |
| 14:18:11 | sean-k-mooney | if we were to assume this was liniar then i think it would be accpetable | |
| 14:18:13 | artom | *numbers | |
| 14:19:09 | dansmith | so, if we just convert to migrate-on-load, we don't take any overhead for string searching at all, migrate only the instances that need it, and are assured that they have migrated all instances by the end of the cycle, right? | |
| 14:19:22 | dansmith | even with nova-manage, we can't make them run it without a blocker migration (which is also expensive) | |
| 14:19:48 | belmoreira | in this case nova_topology is not defined, but may help in the analysis: | |
| 14:19:55 | belmoreira | select count(*) from instance_extra where deleted = 0; #1573 | |
| 14:19:55 | belmoreira | select count(*) from compute_nodes nodes; #88 | |
| 14:19:57 | belmoreira | select * from instance_extra where deleted = 0 and numa_topology is not null and numa_topology like "%nova_object.name%"; #took 106 ms | |
| 14:19:58 | dansmith | if we did that, stephenfin could just remove his nova-manage bits entirely, no impact for anyone that doesn't have old instances | |
| 14:20:35 | stephenfin | Yeah, I can do that too. Let me see if I can wrangle something up | |
| 14:20:39 | artom | dansmith, the end of cycle stuff is complicated by FFUs and operators skipping releases, no? | |
| 14:20:47 | sean-k-mooney | ya if we migrate on load that also works but the only realy implciation is keeping that for a relase or two for FFU | |
| 14:21:00 | dansmith | artom: ah, yeah, good point... | |
| 14:21:34 | artom | So 2 or 3 cycles, I guess | |
| 14:21:39 | dansmith | artom: if we had migrate-on-load for a while, then it'd be fine, but that's the problem trying to do the switch quickly | |
| 14:21:41 | sean-k-mooney | we coudl do both e.g. do the migrate on load and then wen we drop that provide a nova manange command with a blocker migration | |
| 14:22:15 | dansmith | sean-k-mooney: stephenfin has been trying to get this done for a long time so we're trying not to make this a career-long arc | |
| 14:22:46 | artom | dansmith, it's a thing he'll bequeath to his grandchildren | |
| 14:23:08 | sean-k-mooney | yep i know if this was a few weeks ato i woudl have suggeted doing the migrate on load in ussuri and then the blocker/migrate command in victoria | |
| 14:23:16 | stephenfin | 826 days | |
| 14:23:55 | stephenfin | oh my, I appear to have broken zuul https://review.opendev.org/#/c/724332/ | |
| 14:24:24 | artom | Dayyyyuuuuum | |
| 14:24:30 | sean-k-mooney | hehe let me check with infra | |
| 14:27:43 | sean-k-mooney | zuul is being restart | |
| 14:28:00 | sean-k-mooney | it hit an out of memory issue and they are currently trying to fix it | |
| 14:29:17 | sean-k-mooney | so hold rechecks for a few minutes while they sort this out | |
| 14:29:50 | sean-k-mooney | well clearly his patch ate all the memory | |
| 14:35:00 | sean-k-mooney | ok zuul is back up. changes running before 14:00 UTC have been requed anything uploaded or approved bettween 14:00 and 14:30 needs to be rechecked | |
| 14:35:19 | sean-k-mooney | infra are going to send a staus update for the same shortly | |
| 14:52:11 | kashyap | sean-k-mooney: Since you've reviewed an older version (PS-5) and a newer one (PS-7), I'll just address the PS-7 bits here: https://review.opendev.org/#/c/631154/ | |
| 14:52:15 | kashyap | sean-k-mooney: That okay? | |
| 14:55:54 | sean-k-mooney | kashyap: am sure | |
| 14:56:25 | sean-k-mooney | i think i coppied most of the relevent bits although if you read both and just resond on 7 that is fine with me | |
| 14:56:42 | sean-k-mooney | or well update it in version 8 | |
| 14:56:54 | kashyap | sean-k-mooney: While I comment in the spec, on the "increased memory usage" bit -- I knew that thing, but haven't explicitly mentioned it because it requires precise tests, in what scenarios, etc | |
| 14:57:06 | kashyap | You can't just put a generic: "in all cases memory is increased" | |
| 14:57:32 | sean-k-mooney | kashyap: not really even with 1 pci root port dan found it used more memeory the pc | |
| 14:57:34 | kashyap | It requires more testing; so somebody ought to do the "performance testing guy's job"... | |
| 14:57:45 | sean-k-mooney | so i think in all configurtion it has more memory overhead | |
| 14:58:06 | kashyap | sean-k-mooney: Right; I'll mention that, but need to carefully write it in context and with a config example | |
| 14:58:42 | sean-k-mooney | or we can jsut say we expect that q35 will use more memroy as we have never seen a case where it uses less | |
| 14:58:44 | kashyap | sean-k-mooney: Also I don't want us to get sucked into that black-hole and get derailed... | |
| 14:58:56 | kashyap | But that begs the question: "how much more memory than before" | |