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[01:50] <cyphermox> fyi; https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1673350
[01:50] <ubot5> Ubuntu bug 1673350 in multipath-tools (Ubuntu) "dm-queue-length module is not included in installer/initramfs" [Critical,Triaged]
[01:51] <cyphermox> not sure who to assign this to, but I would need dm-queue-length added to multipath-modules
[09:02] <smb> cyphermox, I thought there was some talk about that for s390x... 
[09:07] <smb> cyphermox, ok, I assigned myself and added yakkety. likely should do the udeb changes there as well
[10:29] <xnox> smb, there was this s390x ticket https://bugs.launchpad.net/ubuntu/+source/multipath-tools/+bug/1634161
[10:29] <ubot5> Ubuntu bug 1634161 in multipath-tools (Ubuntu) "Default multipath policy is round-robin, shows considerably worse read throughput compared to using service-time" [Low,Confirmed]
[10:29] <xnox> smb, if you can include service time modules into udeb that would be nice for that ticket.
[10:30] <smb> xnox, Ah could not remember the number but yes service-time now is in the list and I just sent a patch to add queue-length as well
[10:30] <smb> That should be all known ones
[10:32] <smb> xnox, so service-time was added since xenial (or should be, I did not look at the udeb, only the file that should create it)
[10:34] <xnox> ack, let me look at the build-log and the .udeb contents files. one sec.
[10:36] <smb> xnox, -rw-r--r-- root/root     10158 2017-03-08 20:06 ./lib/modules/4.4.0-67-generic/kernel/drivers/md/dm-service-time.ko
[10:36] <xnox> yeap looking sexy.
[10:38] <xnox> cyphermox, would you be able to change defaults to service-time? https://bugs.launchpad.net/ubuntu/+source/multipath-tools/+bug/1634161
[10:38] <ubot5> Ubuntu bug 1634161 in multipath-tools (Ubuntu) "Default multipath policy is round-robin, shows considerably worse read throughput compared to using service-time" [Low,Confirmed]
[10:38] <xnox> in multipath-tools, or shall i?
[10:38]  * xnox is not sure if we should be doing this this close to release.....
[10:48] <apw> xnox, i doubt anyone will have specific testing before now using the existing default, it is a pretty nieche thing
[10:51] <xnox> apw, what do you mean? as far as I understand upstream multipath-tools default is service-time; yet we switch to round-robin. And there is some tests/benchmarks done in the bug report indicating that service-time is better.
[10:51] <xnox> so which testing are you referring to?
[10:52] <xnox> as in testing service-time to make sure it is better?
[10:58] <smb> xnox, apw I would think that the mainframe people have a good history of using dm-queue-length (initially at least) or dm-service-time. Those both would generally be better handling variations in IO time on different paths. While round-robin dumbly switches every 1000 requests
[10:58] <apw> or testing it either way
[10:59] <apw> i mean changing is not so bad imo
[11:01] <smb> Yeah I would not really expect too horrific issues
[11:04] <smb> IIRC it should be possible to change the balancer even post-installation via multipath.conf...
[11:41] <xnox> correct. but we should use sane default
[13:13] <cyphermox> xnox: I'll look at it, there's another fix I need to do in multipath-tools anyway
[13:15] <cyphermox> ah, I see
[13:16] <cyphermox> yeah, it was round-robin only because service-time wasn't available in wily
[13:16] <xnox> i think consensus above it to just drop the patch; such that we use the upstream default of service-time by default. it is in udebs at least in xenial-release and up.
[13:18] <cyphermox> yup
[13:19] <cyphermox> the fact that it's still round-robin instead is a bug
[13:19] <cyphermox> I'll fix this while also fixing queue-length
[13:20] <cyphermox> smb: does dm_emc still exist anywhere?
[13:21] <cyphermox> (IIRC it doesn't, but trying to make sure)
[13:21] <smb> cyphermox, hm... don't think so... though maybe you mean the device handler... give me a sec
[13:22] <smb> cyphermox, scsi_dh_emc.ko
[13:23] <cyphermox> nah, really "dm-emc"
[13:23] <cyphermox> it used to be a module, and I think I removed it in d-i already
[13:23] <smb> cyphermox, cannot even remember that
[13:23] <cyphermox> yep
[13:23] <cyphermox>     - Remove dm-emc from the multipath modules, since it's gone since
[13:23] <cyphermox>       2.6.27.
[13:23] <cyphermox> if I didn't lie when I wrote that
[13:24] <smb> heh
[13:28] <smb> cyphermox, though I really think that if dm-emc was multipath related then it likely was what scsi-dh-emc is now (and those are at least in scsi modules)
[13:28] <cyphermox> yup, I agree
[13:36] <cyphermox> the SRU for service-time is going to be yucky
[13:41] <cyphermox> xnox: fyi, will upload in a minute just being careful and building locally first.
[13:42] <xnox> cyphermox, why would SRU for service-time be yucky? no change to kernel or udebs.... just a flip of default.
[13:50] <cyphermox> yeah, a flip of default which will flip running systems.
[13:50] <cyphermox> ie. you could get better throughput or explosions.
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