SEO

re
by doing things like `dd if=/dev/urandom of=/dev/null bs=2048k`
one can easily hog a system or even worse on smp where time
stalls horribly as well (assuming dd endsup on the cpu>0).
this way dd is almost unnoticable (on a fast amd64 of course
and throughput drops from 900k/s to about half of it that is
barely critical anyhow...
this is also similar to what freebsd does...
cu

--
paranoic mickey (my employers have changed but, the name has remained)

Index: rnd.c
================================================== =================
RCS file: /cvs/src/sys/dev/rnd.c,v
retrieving revision 1.82
diff -u -r1.82 rnd.c
--- rnd.c 17 Jun 2007 21:22:04 -0000 1.82
+++ rnd.c 4 Sep 2007 15:05:51 -0000
@@ -940,8 +940,7 @@
int
randomread(dev_t dev, struct uio *uio, int ioflag)
{
- int ret = 0;
- int i;
+ int i, cnt, ret = 0;
u_int32_t *buf;

if (uio->uio_resid == 0)
@@ -949,8 +948,12 @@

MALLOC(buf, u_int32_t *, POOLBYTES, M_TEMP, M_WAITOK);

- while (!ret && uio->uio_resid > 0) {
- int n = min(POOLBYTES, uio->uio_resid);
+ cnt = uio->uio_resid;
+ if (cnt > PAGE_SIZE)
+ cnt = PAGE_SIZE;
+
+ while (!ret && cnt > 0) {
+ int n = min(POOLBYTES, cnt);

switch(minor(dev)) {
case RND_RND:
@@ -1009,8 +1012,9 @@
default:
ret = ENXIO;
}
- if (n != 0 && ret == 0)
- ret = uiomove((caddr_t)buf, n, uio);
+ if (n != 0 && ret == 0 &&
+ !(ret = uiomove((caddr_t)buf, n, uio)))
+ cnt -= n;
}

FREE(buf, M_TEMP);