random(4) confusions

Dan Nelson dnelson at allantgroup.com
Mon Jun 19 14:24:28 UTC 2006

In the last episode (Jun 19), no at spam@mgedv.net said:
> if i run man 4 random, i'll get the following:
>      The kern.random.sys.burst variable instructs the kernel thread
>      that pro- cesses the harvest queue to tsleep(9) briefly after
>      that many events have been processed.  This helps prevent the
>      random device from being so com- pute-bound that it takes over
>      all processing ability.  A value of 0 (zero) is treated as
>      infinity, and will only allow the kernel to pause if the queue
>      is empty.  Only values in the range [0..20] are accepted.
> if i try to read/set this setting, sysctl returns:
> sysctl: unknown oid 'kern.random.sys.burst'
> what's wrong, my kernel or the manpage?
> [6.1-RELEASE/i386]

>From looking at commit logs, the manpage wasn't updated to remove the
reference to that sysctl when it was obsoleted:

  RCS file: /home/ncvs/src/sys/dev/random/randomdev.c,v
  revision 1.45
  date: 2003/11/17 23:02:21;  author: markm;  state: Exp;  lines: +92 -101

  Overhaul the entropy device:

  o There is no need to break up the event harvesting into ${burst}
    sized chunks, so retire that feature.

	Dan Nelson
	dnelson at allantgroup.com

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