On Thu, Oct 13, 2016 at 08:43:30AM -0400, Laurence Oberman wrote: > > > Hello > > This patch reverts commit 3e22760d4db6fd89e0be46c3d132390a251da9c6. > > This revert came about because of efforts by Ewan Milne, Curtis Taylor and I. > In researching this issue, significant performance issues were seen on large CPU count > systems using the software FCOE stack. > Hannes also weighed in. > > The same was not apparent on much smaller low count CPU systems. > The behavior introduced by commit 3e22760d4db6fd89e0be46c3d132390a251da9c6 lands sup with large > count CPU systems seeing continual blk_requeue_request() calls due to ML_QUEUE_HOST_BUSY. > > From Ewan: > > fc_exch_alloc() used to try all the available exchange managers in the > list for an available exchange id, but this was changed in 2010 so that > if the first matched exchange manager couldn't allocate one, it fails > and we end up returning host busy. This was due to commit: > > Setting the ddp_min module parameter to fcoe to 128MB prevents the ->match > function from permitting the use of the offload exchange manager for the frame, > and we no longer see the problem with host busy status, since it uses the > larger non-offloaded pool. > > Reverting commit 3e22760d4db6fd89e0be46c3d132390a251da9c6 was tested to also > prevent the host busy issue due to failing allocations. > > Suggested-by: Ewan Milne <emilne@xxxxxxxxxx> > Suggested-by: Curtis Taylor <cjt@xxxxxxxxxx> > Tested-by: Laurence Oberman <loberman@xxxxxxxxxx> > Signed-off-by: Laurence Oberman <loberman@xxxxxxxxxx> > Acked-by: Johannes Thumshirn <jth@xxxxxxxxxx> -- Johannes Thumshirn Storage jthumshirn@xxxxxxx +49 911 74053 689 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: Felix Imendörffer, Jane Smithard, Graham Norton HRB 21284 (AG Nürnberg) Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850 -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
