Re: [PATCH V3 12/12] block: Introduce zoned I/O scheduler

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On 09/15/2017 12:06 PM, Damien Le Moal wrote:
> The zoned I/O scheduler is mostly identical to mq-deadline and retains
> the same configuration attributes. The main difference is that the
> zoned scheduler will ensure that at any time at most one write request
> per sequential zone is in flight (has been dispatched to the disk) in
> order to protect against potential sequential write reordering
> resulting from the concurrent execution of request dispatch by multiple
> contexts.
> 
> This is achieved similarly to the legacy SCSI I/O path by write locking
> zones when a write requests is issued. Subsequent writes to the same
> zone have to wait for the completion of the previously issued write
> before being in turn dispatched to the disk. This ensures that
> sequential writes are processed in the correct order without needing
> any modification to the execution model of blk-mq. In addition, this
> also protects against write reordering at the HBA level (e.g. AHCI).
> 
> Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx>
> ---
>  Documentation/block/zoned-iosched.txt |  48 ++
>  block/Kconfig.iosched                 |  12 +
>  block/Makefile                        |   1 +
>  block/zoned-iosched.c                 | 925 ++++++++++++++++++++++++++++++++++
>  4 files changed, 986 insertions(+)
>  create mode 100644 Documentation/block/zoned-iosched.txt
>  create mode 100644 block/zoned-iosched.c
> 
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
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)



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