Re: [PATCH 2/6] libata: Report supported TRIM payload size

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On Fri, Aug 20, 2010 at 9:53 AM, Mark Lord <kernel@xxxxxxxxxxxx> wrote:
> On 10-08-20 04:58 AM, Christoph Hellwig wrote:
>>
>> On Thu, Aug 19, 2010 at 05:50:11PM -0400, Mark Lord wrote:
>>>
>>> On 10-08-19 02:05 PM, Martin K. Petersen wrote:
>>>>
>>>> I'm only aware of one drive that currently
>>>> supports more than 512 bytes of payload and it also caps at 4KB.
>>>
>>> SSDs based upon the Indilinx Barefoot controller support
>>> more or less "infinite" payload for TRIM, with no cap.
>>> But it predates idword[105], so just has a zero there.
>>
>> Is there an easy way to identify them?  If so we could add a quirk
>> for them if it provides enough benefit.
>
>
> Each brand/model identifies itself differently.
> But we could start a whitelist on based on the model name field
> from the ATA identify data.
>
> The OCZ VERTEX drives I have here, identify themselves as "OCZ-VERTEX",
> and accept very very long payloads (no limit?).
>
> The OCZ VERTEX-LE drives here do have a limit, of 8 sectors,
> and identify themselves as "OCZ VERTEX-LE" in that field.
>
> That's what hdparm-9.30 uses to figure out the max TRIM payloads,
> in the absence of a value in word 105.
>
> Cheers
>

A whitelist to enable large contiguous range trims via 8 512B-block
payloads seems useful for those devices that don't support word 105.
(ie. 4KB payload)

But, I doubt there is enough observable performance advantage to
justify reworking the internal SCSI-ATA translation mechanism in the
kernel to handle larger payloads.   Especially if only one or two SSDs
will accept greater than 4KB of payload to the trim command.

Greg
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