Re: Wanted: Secure-delete utility for Linux
Thomas Kunert (kunert@physik.tu-dresden.de)
Wed, 23 Dec 1998 11:16:12 +0100
Michael Shields wrote:
>
> In article <199812230309.AAA05174@sleipnir.valparaiso.cl>,
> Horst von Brand <vonbrand@sleipnir.valparaiso.cl> wrote:
> > There are faster methods, but I'd guess that the I/O time swamps everything
> > else.
>
> Don't guess; measure.
>
> $ time ./a.out | dd bs=1048576 count=10000 of=/dev/null
> 0+10000 records in
> 0+10000 records out
> Broken pipe
>
> real 0m4.010s
> user 0m3.560s
> sys 0m0.240s
>
> Your program generates roughly 2.5 GB/s on an unloaded Celeron 333.
> (gcc 2.7.2.3, -O2) This exceeds the RAM bandwidth.
>
Don't messure; guess :)
The results can't be worse.
2.5 GB/s, that is 8 Bytes/clockcycle or 2 loops/clockcycle, each loop
consisting of calculation and fwrite-syscall.
Processors can do a _lot_ in one clockcycle nowadays:)
Thomas
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