On Tue, 15 Oct 2002, Johannes Stezenbach wrote: > The ability to choose the implementation at run time sacrifices > inlining, but has obvious performance benefits for the VR41XX-like > platforms. It's also not a special MIPS thing, > e.g. linuxthreads/sysdeps/<platform>/pt-machine.h has the > HAS_COMPARE_AND_SWAP / TEST_FOR_COMPARE_AND_SWAP hooks, > used by e.g. i386. It also introduces an indirect call (jump?) overhead. Anyway, you don't need to sacrifice anything. We may simply assume the universally compatible way is the R3k one (be it sysmips() or whatever, if it gets replaced). Then there is the branch-likely way, which requires branch-likely support (thus excludes R3k-class processors). Then there is the ll/sc way, which requires ll/sc (thus excludes R3k-class processors and ones that lack the ll/sc instructions). And you select the minimum set of features required at the build time. > But all that is of interest only, if VR41XX-like platforms > would use a glibc from a binary distribution like RedHat or > Debian (I use Debian for development, but have a custom > compiled glibc for production use). I wouldn't care of distributions -- if one really needs optimized binaries it may make them be build somehow (either by doing the task oneself or by convincing someone else). > Yes, the kernel changes are not difficult. The difficulty was > to find out the minimal necessary changes. You need to spot all kernel exit points. Until we have R6k support it means "eret" instructions. -- + Maciej W. Rozycki, Technical University of Gdansk, Poland + +--------------------------------------------------------------+ + e-mail: macro@ds2.pg.gda.pl, PGP key available +
