Re: [PATCHv2 05/14] libata: NCQ Encapsulation for READ LOG DMA EXT

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On 04/13/2016 08:07 PM, Tejun Heo wrote:
> On Tue, Apr 12, 2016 at 08:47:49AM +0200, Hannes Reinecke wrote:
>> Recent devices can use NCQ encapsulation for READ LOG DMA EXT,
>> so we should be using it if available.
> 
> Does this have any actual benefits than being new and shiny?  It's
> being called from EH path where we know that no other commands are in
> flight.
> 
Hehe. No, it isn't, if you look closely.
(Or make that: it _shouldn't_, and I've messed it up)
(That's what the 'fpdma' parameter is for)

The benefit is not so much for normal operations, but it'll give us
a performance improvements on SMR drives where we need to issue
READ LOG DMA EXT rather frequently. There we really want to have
them as NCQ commands.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@xxxxxxx			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
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