On 10/13/2016 02:43 PM, 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>
>
> diff --git a/drivers/scsi/libfc/fc_exch.c b/drivers/scsi/libfc/fc_exch.c
> index e72673b..d5c4048 100644
> --- a/drivers/scsi/libfc/fc_exch.c
> +++ b/drivers/scsi/libfc/fc_exch.c
> @@ -892,10 +892,15 @@ static inline struct fc_exch *fc_exch_alloc(struct fc_lport *lport,
> struct fc_frame *fp)
> {
> struct fc_exch_mgr_anchor *ema;
> + struct fc_exch *ep;
>
> - list_for_each_entry(ema, &lport->ema_list, ema_list)
> - if (!ema->match || ema->match(fp))
> - return fc_exch_em_alloc(lport, ema->mp);
> + list_for_each_entry(ema, &lport->ema_list, ema_list) {
> + if (!ema->match || ema->match(fp)) {
> + ep = fc_exch_em_alloc(lport, ema->mp);
> + if (ep)
> + return ep;
> + }
> + }
> return NULL;
> }
>
Reviewed-by: Hannes Reinecke <hare@xxxxxxxx>
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
hare@xxxxxxx +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
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HRB 21284 (AG Nürnberg)
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