Sorry, the last patch won't patch cleanly, I forget to update my 
    -current source before diffing.  A new patch is attached, and it
    also includes reducing the sdize of the entropy ring from 1024 to a
    more reasonable 64.

    Mark, what I said last month still holds... you need to make the random
    code less intrusive to the rest of the system.  You need to do it as a
    matter of course, not as an afterthought.  A better hashing algorithm
    is all well and fine, but doesn't really solve the lots-of-interrupts
    problem, it just moves the bar a little.  It doesn't scale, whereas
    a hard limit on interrupt seeds per second does scale.

    If you need a larger ring for initial seeding, then I recommend adding
    a flag to the harvester.  e.g. manual reseeding would use
    the whole ring, but interrupt seeding would only operate if the current
    number of entries in the ring is < 32 and be a NOP otherwise.  Or
    something like that.  Even 32 could be too large... that would be
    32 x 10 or 320 interrupt seeds a second, which is overkill.  Perhaps
    something like 8 would be better (8 x 10 = maximum of 80 interrupt
    reseeds a second).


Index: yarrow.c
RCS file: /home/ncvs/src/sys/dev/random/yarrow.c,v
retrieving revision 1.31
diff -u -r1.31 yarrow.c
--- yarrow.c    2001/02/11 16:21:35     1.31
+++ yarrow.c    2001/03/12 19:27:02
@@ -104,11 +104,9 @@
        for (;;) {
-               if (harvestring.tail == harvestring.head)
-                       tsleep(&harvestring, PUSER, "rndslp", hz/10);
+               tsleep(&harvestring, PUSER, "rndslp", hz/10);
-               else {
+               if (harvestring.tail != harvestring.head) {
                        /* Suck the harvested entropy out of the queue and hash
                         * it into the appropriate pool.
Index: yarrow.h
RCS file: /home/ncvs/src/sys/dev/random/yarrow.h,v
retrieving revision 1.15
diff -u -r1.15 yarrow.h
--- yarrow.h    2001/02/11 16:21:35     1.15
+++ yarrow.h    2001/03/12 19:27:20
@@ -32,7 +32,7 @@
 /* The ring size _MUST_ be a power of 2 */
-#define HARVEST_RING_SIZE      1024    /* harvest ring buffer size */
+#define HARVEST_RING_SIZE      64      /* harvest ring buffer size */
 #define TIMEBIN                16      /* max value for Pt/t */

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