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Re: [dm-devel] [PATCH, RFC 2/2] dm: support REQ_FLUSH directly



On 08/30/2010 06:45 AM, Jun'ichi Nomura wrote:
> 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?

I did that yesterday.  Will post the patch soon.

Thanks.

-- 
tejun


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