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 
> 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 <emi...@redhat.com>
> Suggested-by: Curtis Taylor <c...@us.ibm.com>
> Tested-by: Laurence Oberman <lober...@redhat.com>
> Signed-off-by: Laurence Oberman <lober...@redhat.com>

Acked-by: Johannes Thumshirn <j...@kernel.org>

Johannes Thumshirn                                          Storage
jthumsh...@suse.de                                +49 911 74053 689
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