On Thu, Jul 04, 2002 at 10:47:41AM +0200, Kevin D. Kissell wrote: > The R5900 kernel for the Playstation 2 does not use system > calls. It uses a memory-mapped pseudo-device hack that > the guys at Sony came up with, which is much faster. We > at MIPS came up with an even faster hack which uses > the destruction of a "k" register value, but which requires > the branch-likely instruction and thus only workson > MIPS II CPUs and above (R39xxx, R4xxx, R5xxx, > but not the classic R3K). See my message > "Re: patches for test-and-set without ll/sc" of January 22. > > I consider it to be very important for MIPS/Linux > that the embedded/workstation kernel and libraries > merge with the Playstation 2 "consumer" Linux, and > I don't think that will happen if we try to push the > PS2 people to use something far less efficient than > what they already have. "Entia non sunt multiplicanda > praeter necessitatem", as a wise old guy once said, > but could we not consider a MIPS/Linux universe > where R3000 binaries use system calls, non-LL/SC > MIPSII+ binaries use k-register destruction, real, > manly, MIPS binaries use LL/SC instructions, and > where the MIPS/Linux kernel (a) supports an appropriate > system call, (b) makes a contract with userland to > destroy k-regs predictably, and (c) contains the > emulation logic for LL/SC? That should give us > full cross-platform binary compatibility, with optimal > performance on each platform when an appropriately > configured set of libraries and tools is installed. No, Sony's ABI isn't MP proof and will break silently on MP systems. As such I can't consider it anything else but a hack. sysmips(MIPS_ATOMIC_SET, ...) and ll/sc however are MP proof. Ralf
