Date: Mon, 16 Oct 1995 21:02:12 +0200 From: Mark Murray <mark@grondar.za> To: Bruce Evans <bde@zeta.org.au> Cc: hackers@FreeBSD.org Subject: Re: Creating a /dev/random Message-ID: <199510161902.VAA27145@grumble.grondar.za>
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> To avoid this, use the existing buffer `zbuf', which is freed correctly. > There is no need for another variable - local variables are per process. > Perhaps `zbuf' should be renamed `buf'. I don't understand something here - what happens if the one process is reading both /dev/zero and /dev/random? will the two not then try to share buf/zbuf and screw up? > Hmm, now I know why /dev/zero is so slow. The buffer is bzeroed for > every call. The buffer size is 4K, so reads of about 4K are about > twice as slow as they could by and reads of 1 byte are very slow > because 4K is bzeroed for each byte read. Reserving a page for the > zero buffer would be a bit wasteful and the copyout to move the data > is inelegant anyway. Perhaps there should be a zeroout() function to > optimize this important (;-) device. ...or only c bytes should be zero'ed out? M -- Mark Murray 46 Harvey Rd, Claremont, Cape Town 7700, South Africa +27 21 61-3768 GMT+0200 Finger mark@grumble.grondar.za for PGP key
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