Re: [RFC PATCH v4 9/9] printk: use a new ringbuffer implementation

Linus Torvalds
2019-08-09T01:16:19Z

On Thu, Aug 8, 2019 at 5:48 PM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> I've never tried, but are you saying that even with the "10 second
> hold" the laptop's DRAM may still have old data that is accessible?

The power doesn't go off when you *start* the 10s hold. It goes off
after ten seconds.

So power is off only for the time it then takes you to press the power
button again to turn it on again. So just a second or two if you react
quickly to the "ok, power light finally went off". Longer if you
don't.

But yes, DRAM has retention time in the seconds. See for example

https://www.pdl.cmu.edu/PDL-FTP/NVM/dram-retention_isca13.pdf

and look at the kinds of times they are looking at - their graphs
aren't in milliseconds, they are in 1-5 seconds (and the retention is
pretty high for that time).

But I don't know what a power-off-in-laptop scenario really looks like..

Linus