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| author | rwatson <rwatson@FreeBSD.org> | 2004-10-18 19:29:13 +0000 |
|---|---|---|
| committer | rwatson <rwatson@FreeBSD.org> | 2004-10-18 19:29:13 +0000 |
| commit | 7b853afb002723c73c5121562d0e6da52a480cc5 (patch) | |
| tree | 742d82a474c6d0866e99ab6b048456daac520052 /sys/dev/random | |
| parent | d7592a9bb71c5d4e974dc936db80faaa5291b5cd (diff) | |
| download | FreeBSD-src-7b853afb002723c73c5121562d0e6da52a480cc5.zip FreeBSD-src-7b853afb002723c73c5121562d0e6da52a480cc5.tar.gz | |
Annotate that get_cyclecount() can be expensive on some platforms,
which juxtaposes nicely with the comment just above on how the
harvest function must be cheap.
Diffstat (limited to 'sys/dev/random')
| -rw-r--r-- | sys/dev/random/harvest.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/sys/dev/random/harvest.c b/sys/dev/random/harvest.c index 0ffa83e..d783065 100644 --- a/sys/dev/random/harvest.c +++ b/sys/dev/random/harvest.c @@ -77,6 +77,10 @@ random_yarrow_deinit_harvester(void) * not do anything slow in here! * Implemented as in indirect call to allow non-inclusion of * the entropy device. + * + * XXXRW: get_cyclecount() is cheap on most modern hardware, where cycle + * counters are built in, but on older hardware it will do a real time clock + * read which can be quite expensive. */ void random_harvest(void *entropy, u_int count, u_int bits, u_int frac, |
