From: Hannes Reinecke <hare@suse.de>
To: Mike Christie <michaelc@cs.wisc.edu>
Cc: James Bottomley <jbottomley@parallels.com>,
Sean Stewart <sean.stewart@netapp.com>,
Martin George <marting@netapp.com>,
linux-scsi@vger.kernel.org
Subject: Re: [PATCH 04/16] scsi_dh_alua: Make stpg synchronous
Date: Wed, 12 Feb 2014 16:29:23 +0100 [thread overview]
Message-ID: <52FB9353.7040807@suse.de> (raw)
In-Reply-To: <52F43CD7.5050900@cs.wisc.edu>
On 02/07/2014 02:54 AM, Mike Christie wrote:
> On 02/06/2014 07:24 PM, Mike Christie wrote:
>> On 01/31/2014 03:29 AM, Hannes Reinecke wrote:
>>> We should be issuing STPG synchronously as we need to
>>> evaluate the return code on failure.
>>>
>>> Signed-off-by: Hannes Reinecke <hare@suse.de>
>>
>> I think we need to also make dm-mpath.c use a non-ordered workqueue for
>> kmpath_handlerd. With this patch and the current ordered workqueue in
>> dm-mpath I think we will only be able to do one STPG at a time. I think
>> if we use a normal old non-ordered workqueue then we would be limited to
>> have max_active STPGs executing.
>
> I goofed and commented in the order I saw the patches :) I take this
> comment back for this patch, because I see in 16/16 you added a new
> workqueue to scsi_dh_alua to do rtpgs and stpgs.
>
> For 16/16 though, do we want to make kmpath_aluad a non single threaded
> workqueue? It looks like max_active for single threaded is only one work
> at a time too.
>
Well, that was by intention.
The workqueue will be triggered very infrequently (basically for
every path switch).
For implicit ALUA we just need to issue a RTPG to get the new path
status; there we might be suffering from single threaded behaviour.
But we need to issue it only once and it should be processed
reasonably fast.
For explicit ALUA we'll have to send an STPG, which has potentially
system-wide implications. So sending several to (supposedly)
different targets might actually be contraproductive, as the first
might have already set the status for the second call.
Here we most definitely _want_ serialisation to avoid superfluous STPGs.
So for now I think we can stick with the single threaded workqueue,
and can revise this later if it's found to be a scalability issue.
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@suse.de +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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next prev parent reply other threads:[~2014-02-12 15:29 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-31 9:29 [PATCHv2 00/16] scsi_dh_alua updates Hannes Reinecke
2014-01-31 9:29 ` [PATCH 01/16] scsi_dh_alua: Improve error handling Hannes Reinecke
2014-02-14 11:16 ` Bart Van Assche
2014-02-14 11:32 ` Hannes Reinecke
2014-03-06 23:43 ` Jeremy Linton
2014-03-07 7:12 ` Hannes Reinecke
2014-03-07 15:46 ` Jeremy Linton
2014-01-31 9:29 ` [PATCH 02/16] scsi_dh_alua: use flag for RTPG extended header Hannes Reinecke
2014-01-31 9:29 ` [PATCH 03/16] scsi_dh_alua: Pass buffer as function argument Hannes Reinecke
2014-02-14 11:22 ` Bart Van Assche
2014-02-14 11:36 ` Hannes Reinecke
2014-01-31 9:29 ` [PATCH 04/16] scsi_dh_alua: Make stpg synchronous Hannes Reinecke
2014-02-07 1:24 ` Mike Christie
2014-02-07 1:54 ` Mike Christie
2014-02-12 15:29 ` Hannes Reinecke [this message]
2014-02-12 16:11 ` Mike Christie
2014-02-12 16:26 ` Mike Christie
2014-02-12 17:31 ` Mike Christie
2014-02-13 9:31 ` Hannes Reinecke
2014-02-14 11:37 ` Bart Van Assche
2014-02-14 11:53 ` Hannes Reinecke
2014-02-14 18:21 ` Mike Christie
2014-02-19 8:09 ` Hannes Reinecke
2014-02-14 17:17 ` Mike Christie
2014-02-14 11:27 ` Bart Van Assche
2014-02-14 11:38 ` Hannes Reinecke
2014-01-31 9:29 ` [PATCH 05/16] scsi_dh_alua: put sense buffer on stack Hannes Reinecke
2014-01-31 9:29 ` [PATCH 06/16] scsi_dh_alua: use local buffer for VPD inquiry Hannes Reinecke
2014-02-13 9:51 ` Maurizio Lombardi
2014-02-13 10:10 ` Hannes Reinecke
2014-02-14 11:41 ` Bart Van Assche
2014-01-31 9:29 ` [PATCH 07/16] scsi_dh_alua: Use separate alua_port_group structure Hannes Reinecke
2014-02-14 11:56 ` Bart Van Assche
2014-02-14 12:16 ` Hannes Reinecke
2014-02-14 16:12 ` Hannes Reinecke
2014-02-14 17:42 ` Bart Van Assche
2014-01-31 9:29 ` [PATCH 08/16] scsi_dh_alua: parse target device id Hannes Reinecke
2014-02-14 12:09 ` Bart Van Assche
2014-02-14 12:21 ` Hannes Reinecke
2014-02-17 14:05 ` Bart Van Assche
2014-02-17 14:09 ` Hannes Reinecke
2014-02-17 14:27 ` Bart Van Assche
2014-02-17 14:33 ` Hannes Reinecke
2014-02-18 7:26 ` Bart Van Assche
2014-01-31 9:29 ` [PATCH 09/16] scsi_dh_alua: simplify sense code handling Hannes Reinecke
2014-01-31 9:29 ` [PATCH 10/16] scsi_dh_alua: Do not attach to management devices Hannes Reinecke
2014-01-31 9:29 ` [PATCH 11/16] scsi_dh_alua: multipath failover fails with error 15 Hannes Reinecke
2015-03-30 12:30 ` Bart Van Assche
2015-03-30 12:32 ` Hannes Reinecke
2014-01-31 9:29 ` [PATCH 12/16] scsi_dh: return individual errors in scsi_dh_activate() Hannes Reinecke
2014-01-31 9:29 ` [PATCH 13/16] scsi_dh_alua: Clarify logging message Hannes Reinecke
2014-01-31 9:29 ` [PATCH 14/16] scsi_dh: invoke callback if ->activate is not present Hannes Reinecke
2014-01-31 9:29 ` [PATCH 15/16] scsi_dh_alua: revert commit a8e5a2d593cbfccf530c3382c2c328d2edaa7b66 Hannes Reinecke
2014-01-31 9:30 ` [PATCH 16/16] scsi_dh_alua: Use workqueue for RTPG Hannes Reinecke
2014-02-14 19:03 ` Bart Van Assche
2014-04-29 21:47 ` Stewart, Sean
2014-05-08 7:04 ` Hannes Reinecke
2014-03-02 9:10 ` [PATCHv2 00/16] scsi_dh_alua updates Bart Van Assche
-- strict thread matches above, loose matches on Subject: below --
2013-12-20 12:13 [PATCH " Hannes Reinecke
2013-12-20 12:13 ` [PATCH 04/16] scsi_dh_alua: Make stpg synchronous Hannes Reinecke
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