Subject: rnd_add_uint32()
To: enami tsugutomo <enami@sm.sony.co.jp>
From: None <itojun@iijlab.net>
List: tech-kern
Date: 08/21/2002 13:29:42
>Jun-ichiro itojun Hagino <itojun@netbsd.org> writes:
>
>> Module Name: syssrc
>> Committed By: itojun
>> Date: Tue Aug 20 00:35:47 UTC 2002
>>
>> Modified Files:
>> syssrc/sys/dev/pci: if_sip.c
>>
>> Log Message:
>> attach random number source.
>>
>>
>> To generate a diff of this commit:
>> cvs rdiff -r1.64 -r1.65 syssrc/sys/dev/pci/if_sip.c
>
>You are calling rnd_add_uint32() within the loop in interrupt routine
>but does the clock spent in each iteration so vary?
rnd_add_uint32() does two things:
- add CPU free-running clock value to entropy pool
- add the specified number to entropy pool
by calling it on each iteration i was trying to do the latter,
since there's no meaningful random value outside of the loop.
the former is the one you are talking about, and i guess you are
right that the former value won't change that much;
sys/dev/rnd.c:rnd_counter(). even though, putting data intoentropy
pool do help us stir random number pool.
it is a difficult tradeoff. if anyone with gsip card could measure
performance impact, it would be helpful.
itojun