On 21/05/12 11:16, Yaniv Kaul wrote:
On 05/21/2012 11:08 AM, Doron Fediuck wrote:
On 21/05/12 11:01, Dor Laor wrote:
On 05/21/2012 10:58 AM, Doron Fediuck wrote:
On 21/05/12 01:45, Andrew Cathrow wrote:
----- Original Message -----
From: "Doron Fediuck"<dfediuck@redhat.com> To: dlaor@redhat.com Cc: engine-devel@ovirt.org Sent: Sunday, May 20, 2012 5:49:08 PM Subject: Re: [Engine-devel] CPU Pinning @engine
On 20/05/12 21:41, Dor Laor wrote: > On 05/17/2012 11:15 PM, Doron Fediuck wrote: >> On 17/05/12 20:28, Ayal Baron wrote: >>> "Live migration will not be supported for such VM's." >>> >>> Migration will work on homogeneous clusters so this should not be >>> enforced (not limited to VMs which are pinned to host) just give >>> a warning. >>> >> I agree, but if we wish to ping vCPUx to pCPUy in host a, we >> cannot ensure to have the same in host b, >> since it may have pCPUy too busy, so performance will degrade. >> Also, I hope you saw my general comment > Performance may degrade on any migration to loaded host regardless > of pinning. > > There is not need to forbid migration. Instead, the SLA assurance > policy should verify the dedicated resources and match the target > w/ the guarantee and decide according to this. > Thanks for the input. We may start with migration blocked in a configurable manner, so people who wish migrate to work will simply set the relevant configuration key. As for looking for a matched CPU, will add it as p2. We shouldn't block migration If a user wants to not migrate a cpu pinned VM then let them use the non-migratable flag in the UI.
We're not blocking migration, we're allowing pinning (for now) only for non-migrative VM's. For p2 we'll verify destination host has the relevant pinning capacity, which will allow pinning for migrative VM's as well.
IMHO the order should be the opposite - if the user likes to migrate a pinned VM, let him (you can pop some message if you like). I'll check it with UI guys (AFAIK engine UI has no pop-ups). Also, I prefer safe than sorry. So start with a safe working pinning for pinned-to-host VMs, and then push the envelope.
Safe is letting the user migrate. It may or may not succeed (I'd worry it may put a host into Error state - I hope we've removed this state). This is a pure speculation. If I'm pinning a specific VM to a specific host, and its vCPUS into specific pCPUs, how can live migration be considered a safe thing? If I pinned to host, this is a violation of my request. Now, let's say I didn't pin to host, but I ask for specific vCPUS pinning into specific pCPUs. For now, there's no guarantee the destination host will have a relevant CPU capacity (maybe even topology), so CPU pinning may not work, which is also a violation of my request. Is live migration really the safe thing to do here??? Why not alert me so I could manually migrate to where I think is better? Having that said, I'm reminding you the somewhere earlier in this thread I wrote we'll make the constraint of cpu pinning allowed only on pinned-to-host VMs configurable, so people who wish to walk on wild side, can give it a go.
Sorry is when you wish you had done so initially. ;-) In this case, I disagree as this is configurable.
Y.
>> about starting with a humble solution and gradually improving. In >> this context (auto)numa can help us, >> so we better do numa than handle migration for basic mode, risking >> performance issues. >> >>> ----- Original Message ----- >>>> From: "Doron Fediuck"<dfediuck@redhat.com> >>>> To: engine-devel@ovirt.org >>>> Sent: Thursday, May 17, 2012 2:42:46 PM >>>> Subject: [Engine-devel] CPU Pinning @engine >>>> >>>> Hi All, >>>> Currently the VDSM has a CPU pinning hook. >>>> We'd like to add better support of it into the engine itself. >>>> Here's a design draft to cover it: >>>> http://www.ovirt.org/wiki/Features/Design/cpu-pinning >>>> >>>> Please review and comment if needed. >>>> >>>> Thanks! >>>> -- >>>> >>>> /d >>>> >>>> Never say "OOPS!" always say "Ah, Interesting!" >>>> _______________________________________________ >>>> Engine-devel mailing list >>>> Engine-devel@ovirt.org >>>> http://lists.ovirt.org/mailman/listinfo/engine-devel >>>> >>> _______________________________________________ >>> Engine-devel mailing list >>> Engine-devel@ovirt.org >>> http://lists.ovirt.org/mailman/listinfo/engine-devel >>
--
/d
Never say "OOPS!" always say "Ah, Interesting!" _______________________________________________ Engine-devel mailing list Engine-devel@ovirt.org http://lists.ovirt.org/mailman/listinfo/engine-devel
-- /d Why doesn't DOS ever say "EXCELLENT command or filename!"