On Tue, 12 Jun 2018, Ævar Arnfjörð Bjarmason wrote:

>> From a performance standpoint, I have to say (once more) that crypto
>> performance actually mattered a lot less than I originally thought it
>> would. Yes, there are phases that do care, but they are rare.
>
> One real-world case is rebasing[1]. As noted in that E-Mail of mine a
> year ago we can use SHA1DC v.s. OpenSSL as a stand-in for the sort of
> performance difference we might expect between hash functions, although
> as you note this doesn't account for the difference in length.

when you are rebasing, how many hashes do you need to calculate? a few dozen, a 
few hundred, a few thousand, a few hundered thousand?

If the common uses of rebasing are on the low end, then the fact that the hash 
takes a bit longer won't matter much because the entire job is so fast.

And at the high end, I/O will probably dominate.

so where does it really make a human visible difference?

David Lang