[dm-devel] [PATCH, RFC 2/2] dm: support REQ_FLUSH directly
Jun'ichi Nomura
j-nomura at ce.jp.nec.com
Mon Aug 30 04:45:20 UTC 2010
Hi Mike,
(08/27/10 23:13), Mike Snitzer wrote:
>> If there will be no need for supporting a request-based target
>> with num_flush_requests > 1, the special handling of flush
>> can be removed.
>>
>> And since there is no such target in the current tree,
>> I don't object if you remove that part of code for good reason.
>
> OK, certainly something to keep in mind. But _really_ knowing the
> multipath FLUSH+FUA performance difference (extra special-case code vs
> none) requires a full FLUSH conversion of request-based DM anyway.
>
> In general, request-based DM's barrier/flush code does carry a certain
> maintenance overhead. It is quite a bit of distracting code in the core
> DM which isn't buying us anything.. so we _could_ just remove it and
> never look back (until we have some specific need for num_flush_requests
>> 1 in rq-based DM).
So, I'm not objecting to your idea.
Could you please create a patch to remove that?
Thanks,
--
Jun'ichi Nomura, NEC Corporation
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