Messages in this thread | | | Subject | Re: Question on handling managed IRQs when hotplugging CPUs | From | John Garry <> | Date | Tue, 5 Feb 2019 15:09:28 +0000 |
| |
On 05/02/2019 14:52, Keith Busch wrote: > On Tue, Feb 05, 2019 at 05:24:11AM -0800, John Garry wrote: >> On 04/02/2019 07:12, Hannes Reinecke wrote: >> >> Hi Hannes, >> >>> >>> So, as the user then has to wait for the system to declars 'ready for >>> CPU remove', why can't we just disable the SQ and wait for all I/O to >>> complete? >>> We can make it more fine-grained by just waiting on all outstanding I/O >>> on that SQ to complete, but waiting for all I/O should be good as an >>> initial try. >>> With that we wouldn't need to fiddle with driver internals, and could >>> make it pretty generic. >> >> I don't fully understand this idea - specifically, at which layer would >> we be waiting for all the IO to complete? > > Whichever layer dispatched the IO to a CPU specific context should > be the one to wait for its completion. That should be blk-mq for most > block drivers.
For SCSI devices, unfortunately not all IO sent to the HW originates from blk-mq or any other single entity.
Thanks, John
> > . >
| |