W dniu sob, 21.10.2017 o godzinie 10∶01 +0200, użytkownik Paweł Hajdan, Jr. napisał: > On 20/10/2017 18:15, Michał Górny wrote: > > W dniu pią, 20.10.2017 o godzinie 17∶42 +0200, użytkownik Paweł Hajdan, > > Jr. napisał: > > > Curious, do we have any measurements/estimates of the performance cost? > > > > With a single thread serial processing of all hashes, it's just sum of > > times involved in every hash, i.e. Th = T1 + T2 + T3 + ... You'd have to > > get some numbers to get something smarter out of it. > > > > If we assume we can do N threads, then cost of N algorithms is equal to > > the slowest of them all. Which implies that having N algorithms is > > fastest on systems capable of at least N threads. > > > > Taking a random comparison [1], it seems that SHA3/512 is 3-5 times > > slower than SHA2/512. > > How large part of dependency calculation / other portage's operation is > this though? > > My point is, did profiling turn out hash computation as bottleneck, or > is this more speculative?
Purely speculative. > I'm still in favor of modernizing the hashes, just somewhat skeptical > when performance is being mentioned. > FWICS BLAKE2 can be even 2.5 times faster than SHA2, so we'll probably go with that. In this case, the performance impact will be negligible -- in fact, it should be faster than the current set of three hashes. -- Best regards, Michał Górny
