[stgt] WRITE_SAME aio support

[ronnie sahlberg]

If it is VMWARE then it probably uses WRITESAME10/16 for unmap/discard purposes.

For now, can you try using bs_rdwr instead of bs_aio ?


Longer term I will do a patch for
* add WRITESAME10/16 + unmap support to bs_aio
* make "indicate unmap support based on whether the backend supports it or not"




On Sun, Aug 18, 2013 at 4:57 PM, Moussa Ba (moussaba)
<moussaba at micron.com> wrote:
> The LUN as seen by VMWare shows WRITE_SAME support.   Not sure what is uses for  discard
>
>
> -------- Original message --------
> From: ronnie sahlberg <ronniesahlberg at gmail.com>
> Date: 08/18/2013 16:55 (GMT-08:00)
> To: "Moussa Ba (moussaba)" <moussaba at micron.com>
> Cc: stgt at vger.kernel.org
> Subject: Re: WRITE_SAME aio support
>
>
> Your initiator uses WS10/16 for unmap/discard ?
> (i.e. you mount the filesystem using -o discard in the guest)
>
> STGT currently offers "I support unmapping using both WS10 and 16". We
> probably should only do this
> for backends that supports these operations,  == bs_rdwr.c and not
> indicate support for the others.
>
>
> What we probably need to do here is to make the support for
> WRITESAME10/16 with unmap support optional
> on whether the backend supports it.
> I can look at adding this once I get some other changes in.
>
>
>
> On Wed, Aug 14, 2013 at 2:41 PM, Moussa Ba (moussaba)
> <moussaba at micron.com> wrote:
>> I am seeing a LOT of WRITE_SAME error messages in the tgt logs. I understand it is not implemented for aio, my question is will this affect array performance . We are using tgt to host datastores for a virtualization workload.
>>
>>
>> tgtd: bs_aio_cmd_submit(211) WRITE_SAME not yet supported for AIO backend
>>
>>
>> Moussa
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