Re: [PATCH 08/14] scsi: convert device_busy to atomic_t

2014-07-09 Thread Christoph Hellwig
On Wed, Jul 09, 2014 at 09:49:56AM -0700, James Bottomley wrote: > As far as I can tell from the block MQ, we get one CPU thread per LUN. No, that's entirely incorrect. IFF a device supports multiple hardware queues we only submit I/O from CPUs (there might be more than one) this queue is bound t

Re: [PATCH 08/14] scsi: convert device_busy to atomic_t

2014-07-09 Thread James Bottomley
On Wed, 2014-06-25 at 18:51 +0200, Christoph Hellwig wrote: > Avoid taking the queue_lock to check the per-device queue limit. Instead > we do an atomic_inc_return early on to grab our slot in the queue, > and if nessecary decrement it after finishing all checks. > > Unlike the host and target bu

Re: [PATCH 08/14] scsi: convert device_busy to atomic_t

2014-07-09 Thread Hannes Reinecke
On 06/25/2014 06:51 PM, Christoph Hellwig wrote: Avoid taking the queue_lock to check the per-device queue limit. Instead we do an atomic_inc_return early on to grab our slot in the queue, and if nessecary decrement it after finishing all checks. Unlike the host and target busy counters this do