On 05/08/2010 04:40 AM, Tejun Heo wrote:
On 05/07/2010 11:33 PM, Jeff Garzik wrote:
I'm not sure the usefulness is limited, as it definitely avoids power
spikes on server BIOSen that care.
So, are there actually machines which get affected by this? In that
case, sure, the current behavior is the right one.
The current behavior is the safe, conservative interpretation. The
alternative is risking unwanted power spikes for the sake of boot speed.
I would set a high barrier for taking that risk: polling multiple
hardware vendors about in-the-field SSS usage.
Also, it seems unwise for the Linux SATA driver to do the exact
-opposite- of what the SSS bit intends, by default.
Yeah, well, the thing is that SSS in itself doesn't really indicate
need for staggered spin up. It just says it knows how to.
A valid point, I agree. But absent any other method of communicating
that SSS behavior is desired, activating staggered spin-up based on SSS
is the only logical interpretation, AFAICS. SSS bit set implies SSS
-might- be needed. If SSS might be needed, then one must stagger
spin-up or risk failing to meet the requirement. !SSS is the only case
where you are -guaranteed- not to need staggered spin-up.
Jeff
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