Messages in this thread | | | Date | Wed, 19 Sep 2007 17:39:46 -0400 | From | "Andrew Lutomirski" <> | Subject | Re: A little coding style nugget of joy |
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On 9/19/07, Andi Kleen <andi@firstfloor.org> wrote: > > This is a terrible assumption in general (i.e. if filesize % blocksize > > is close to uniformly distributed). If you remove one byte and the data > > is stored with blocksize B, then you either save zero bytes with > > probability 1-1/B or you save B bytes with probability 1/B. The > > expected number of bytes saved is B*1/B=1. Since expectation is linear, > > if you remove x bytes, the expected number of bytes saved is x (even if > > there is more than one byte removed per file). > > You didn't calculate the probability of actually saving a full block > or not (that's the only thing that matters). I assumed it's relatively > small and can be ignored in practice since the amount of end white > space is negligible compared to total file size.
Sure I did. It's roughly 1/B per byte removed ( = 1/4096 ).
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