Re: [PATCHv6 0/3] New EH command timeout handler

[Christoph Hellwig <hch@infradead.org>]

James, and comments on this?

It would be really good if we could make some progress getting various
infrastructure merged.

On Mon, Sep 02, 2013 at 01:58:35PM +0200, Hannes Reinecke wrote:
> Hi all,
> 
> this patchset implements a new SCSI EH command timeout handler
> which will be sending command aborts inline without actually
> engaging SCSI EH.
> SCSI EH will only be invoked if command abort fails.
> 
> In addition the commands will be returned directly
> if the command abort succeeded, cutting down recovery
> times dramatically.
> 
> With the original SCSI EH I got:
> # time dd if=/dev/zero of=/dev/dm-2 bs=4k count=4k oflag=direct
> 4096+0 records in
> 4096+0 records out
> 16777216 bytes (17 MB) copied, 142.652 s, 118 kB/s
> 
> real	2m22.657s
> user	0m0.013s
> sys	0m0.145s
> 
> With this patchset I got:
> # time dd if=/dev/zero of=/dev/dm-2 bs=4k count=4k oflag=direct
> 4096+0 records in
> 4096+0 records out
> 16777216 bytes (17 MB) copied, 52.1579 s, 322 kB/s
> 
> real	0m52.163s
> user	0m0.012s
> sys	0m0.145s
> 
> Test was to disable RSCN on the target port, disable the
> target port, and then start the 'dd' command as indicated.
> 
> Changes to the original version:
> - Use a private list in scsi_eh_abort_handler to avoid
>   list starvation (pointed out by Joern Engel)
> - Terminate command aborts when the first abort fails
> - Do not attempt command aborts if the host is already in recovery
>   or if the device is removed.
> - Flush abort workqueue if the device is removed.
> 
> Changes to v2:
> - Removed eh_entry initialisation
> - Convert to per-command workqueue
> 
> Changes to v3:
> - Use delayed_work
> - Enable new eh timeout handler for virtio, SAS, and FC
> - Modify logging messages to include scmd pointer
> 
> Changes to v4:
> - Remove stubs when enabling new eh timeout handler
>   for other drivers
> 
> Changes to v5:
> - Enable new eh timeout handler per default
> - Update documentation
> 
> Hannes Reinecke (3):
>   scsi: Fix erratic device offline during EH
>   scsi: improved eh timeout handler
>   scsi_error: Update documentation
> 
>  Documentation/scsi/scsi_eh.txt          |  69 +++++++------
>  Documentation/scsi/scsi_mid_low_api.txt |   9 +-
>  drivers/scsi/scsi.c                     |   9 +-
>  drivers/scsi/scsi_error.c               | 177 ++++++++++++++++++++++++++++----
>  drivers/scsi/scsi_priv.h                |   2 +
>  include/scsi/scsi_cmnd.h                |   1 +
>  include/scsi/scsi_host.h                |   5 +
>  7 files changed, 214 insertions(+), 58 deletions(-)
> 
> -- 
> 1.7.12.4
> 
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