On Sat, 14 Jul 2001, Ralf Baechle wrote: > I'm just making an attempt to re-implement the ll/sc emulation as light > as possible. I hope to get the overhead down to the point were we don't > need _test_and_set anymore - in any case below the overhead of a syscall. > > Have you ever profiled the number of calls to MIPS_ATOMIC_SET or > _test_and_set? They'll be the other factor in a decission. I didn't profile it very extensively, yet when stracing `ls /usr/lib' (fileutils 4.1 linked against glibc 2.2.3) on my system once I yielded ~4500 syscalls of which ~4000 were _test_and_set() (or MIPS_ATOMIC_SET, depending on my kernel/glibc configuration) invocations. Yes, libpthread appears to assume atomic operations are cheap, which is justifiable as they are indeed, for almost every other CPU type. Also I feel having ll and sc opcodes in a pure MIPS I binary is somewhat ugly (e.g. `objdump' won't disassemble them unless a MIPS II+ CPU is specified), but I could probably live with it if performance was not worse. -- + Maciej W. Rozycki, Technical University of Gdansk, Poland + +--------------------------------------------------------------+ + e-mail: macro@ds2.pg.gda.pl, PGP key available +
