On Sat, 20 Jan 2007, Ismail Dönmez wrote:
> 20 Oca 2007 Cts 22:10 tarihinde, Tim Schmielau şunları yazmıştı:
> >
> > Note that these dd "benchmarks" are completely bogus, because the data=20
> > doesn't actually get written to disk in that time. For some enlightening=20
> > data, try
> >
> > time dd if=3D/dev/zero of=3D/tmp/1GB bs=3D1M count=3D1024; time sync
^^^^
> >
> > The dd returns as soon as all data could be buffered in RAM. Only sync=20
> > will show how long it takes to actually write out the data to disk.
> > also explains why you see better results is writeout starts earlier.
>
> Still not that bad:
>
> [~]> time dd if=/dev/zero of=/tmp/1GB bs=1M count=1024;sync
> 1024+0 records in
> 1024+0 records out
> 1073741824 bytes (1,1 GB) copied, 53,3194 s, 20,1 MB/s
>
> real 0m53.517s
> user 0m0.003s
> sys 0m3.193s
>
That's not the point, you still measured the same as before (but you might
have noticed that, after printing the results, the shell prompt took some
time to appear). I appended "time sync" to the command to show that
(depending on the amount of available memory) actually most of the time
is spent in the "sync", not the "dd".
Tim
