On Tue, Sep 10, 2013 at 1:50 PM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> Of course, maybe even the stupid add_device_randomness() is fast
> enough. I just wanted to point out that it definitely isn't some
> optimized thing.
When I posted the patch that mixes in the whole SMBIOS table:
commit d114a33387472555188f142ed8e98acdb8181c6d
Author: Tony Luck <tony.luck@xxxxxxxxx>
Date: Fri Jul 20 13:15:20 2012 -0700
dmi: Feed DMI table to /dev/random driver
I asked whether there was any size issue - as it tends to be a few
kilobytes on laptops and desktops, and tens of kilobytes on servers.
The answer I got back then was not to worry - digesting a few kilobytes
wouldn't be a problem. I just threw in a debug message to check and saw:
dmi_walk_early: added 10342 bytes in 339968 cycles
So a couple of hundred microseconds for me.
There are plenty of machine specific values buried in there (e.g. serial
numbers for all the DIMMs) ... so this looks like a good use of this
much boot time.
-Tony
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