Messages in this thread | | | Date | Sun, 15 Jun 1997 13:29:49 +0200 | From | geerten kuiper <> | Subject | Re: Saving syscall cycles on a Cyrix |
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At 12:23 12/06/97 +0100, Mike Jagdis wrote: >On Thu, 12 Jun 1997, Thomas Koenig wrote: > >> prompted by a discussion on comp.sys.development.system, I had a look >> at entry.S, and found that this can be speeded up significantly for >> a Cyrix. >> >> The problem is that two pushl/popl instructions can't be paired in the >> Cyrix' X and Y pipelines because the esp register gets modified >> in both. >> >> [...] >> >> only takes four, because any two instructions can pair. The same >> goes for the reverse, i.e. the popl instructions. Cyrix patch >> maintainers, are you listening? :-) > >Most modern x86 processors have dual pipelines and can benefit >from similar optimizations. The current gcc isn't particularly >smart about interleaving code paths to avoid "bubbling" in the >pipelines. I've been reading up on such tuning recently and, if >anyone is interested, have hand tuned the rc5 cracking code to >go from ~145K keys/s (on my machine) to ~205K keys/s (yes, you >can get a big difference!). Of course, this is at the assembler >level and the result is, ah, "not easily readable" but even >paying attention to the order you do things in C can show >reasonable gains. Whether such things are good for MIPS, Sparc, >Alpha, PPC etc. as well is another question :-). > > Mike >
You may be interested in David Mosberger's paper on optimizations for Alpha. Some of them work quite well for the higher end x86's as well.
>For those of you who couldn't make it to LinuxExpo '97 but are >interested in making code run fast, my paper is now available at: > > http://www.linuxexpo.org/1997/after/papers/davidm/paper-html/ > >(in addtion to all the other papers available at >http://www.linuxexpo.org/1997/after/papers/). I appended the title & >abstract below. > >Enjoy, > --david
Groeten, Geerten.
Geerten Kuiper | "It is customary to append a signature or Corn. Houtmanstraat 113 | .sig to a mail message, usually containing 2593 RG Den Haag | information on the author, along with a Nederland | joke or a motto." | Olaf Kirch | LINUX Network Administrators Guide
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