On Wed, Jun 25, 2003 at 01:26:38PM +0900, GOTO Masanori wrote: > Performance improvement is _not_ my primary intention.At least it needs to > support libc6-686: > > - LinuxThreads floating stack support. It's ready for i686 and later. > > - NPTL/TLS support. NPTL currently supports i486 and later because > pthread_spin_trylock uses cmpxchgl instruction (well, it's not > difficult to support i386, but imagine pthread on i386 with the > max clock (I recall it was 20MHz?) speed and memory...) > > and so on.
Ah, I was not aware of this. I am very interested in both of these features. > BTW, I also think that 5% performance improvement with optimization is > valuable. It's not easy to accelerate 5% performance without any source > code modification and hardware improvement. In addition, it reduces the > user responce time, I think it's more important than increasing throughput > (= computational speed). 5% may or may not be valuable depending on the cost. Where did this particular figure come from (5%)? > IMHO, the problem is the lack of real data which compares non- optimized > vs optimized binary performance on the actual environment. I often heard > the perfomance improvement issue using gcc optimization like Gentoo, but I > merely saw the real perfomance comparison graph. So, supporting optimized > library is not primary issue for at least libc. I see a lot of handwaving from gentoo users and the like, but no convincing concrete measurements. Most of what I see is: - "I switched from <distribution X> to <optimized toy> and now <foo> is much faster!" - "I run <distribution X> on one PC, and <optimized toy> on the other, and the optimized one is way faster! They're exactly the same hardware except [they're not]" - "I compared an un-optimized build of <foo> (no -O at all) to one compiled with -O27 -pipe -fomit-frame-pointer -funroll-all-loops -march=pentium3 -mcpu=pentium3 -mfpmath=sse -mmmx -msse -mother-options-i-dont-even-understand -mi-didnt-read-the-manual" These claims are usually subjective, but sometimes they come with numbers, which are meaningless because there are so many variables involved. -- - mdz