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[dm-devel] RE: [PATCH 0/4] scsi_dh: Make scsi_dh_activate asynchronous



Hi Chandra,
   Thanks for the patches. Patches applied cleanly on 2.6.31. I am testing the patches right now. Will post the with test results tomorrow.
These are my initial comments. 
1. Patches do not apply on 2.6.32. You may have to regenerate it on 2.6.32.
2. Also, I noticed few errors and warnings while running checkpatch.pl script.  
3. Subject line for patch 3 and 4 may need to be modified. It still says "rdac handler". It should be hp and alua handler. 

Thanks..

> -----Original Message-----
> From: linux-scsi-owner vger kernel org [mailto:linux-scsi-
> owner vger kernel org] On Behalf Of Chandra Seetharaman
> Sent: Tuesday, September 29, 2009 9:08 PM
> To: linux-scsi vger kernel org
> Cc: dm-devel redhat com; Moger, Babu; michaelc cs wisc edu;
> Benoit_Arthur emc com; Eddie Williams steeleye com;
> berthiaume_wayne emc com; Chandra Seetharaman
> Subject: [PATCH 0/4] scsi_dh: Make scsi_dh_activate asynchronous
> 
> Hello All,
> 
> Currently, device handlers process path activation in series. This leads
> to a lot of time delay when more than 100 luns are involved. For example,
> with lsi rdac 100+ luns take about 12-15 minutes. This was found by Moger
> Babu of LSI.
> 
> This time delay can be avoided if we can do the activations
> asynchronously.
> By making scsi_dh_activate() async, we can give the device handlers an
> oppurtunity to decide on how to send the device activation down the wire
> to make the turn around time faster. They can send the commands
> asynchronously or send them in batches.
> 
> I brought up this issue on the mailing list
> (http://marc.info/?l=linux-scsi&m=123888063818755&w=2) and provided a
> set of patch a loooong while back http://marc.info/?l=linux-
> scsi&m=124088712709821&w=2
> 
> This set of patches applies cleanly on 2.6.31 and I tested the rdac
> handler
> on the same.
> 
> Please review and provide comments.
> 
> This set of patched adds asynchronous support for rdac, hp, and alua
> handlers.
> 
> Didn't add async support for EMC for the following reasons:
>  - EMC handler is getting more hairy (when I try to move to _nowait())
>  - I do not know if EMC has a special command to group them (like rdac).
>  - I wasn't sure if EMC has this problem in the first place ( I did not
> get
>    any response from EMC).
> Can somebody from EMC comment, please.
> 
> Thanks & Regards,
> 
> chandra
> 
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