* Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote: > On Wednesday 10 December 2008 16:19:21 Andrew Morton wrote: > > Rusty, Christoph: talk to me. If we add a new user of local_t in core > > kernel, will we regret it? > > Interesting. There's new local_t infrastructure, but it's not used. > > Here's a benchmark patch showing some results. x86 is pretty close to > optimal already, though my results on Power show atomic_long is a bad choice > there. > > I'll do an audit of the users, then send out some local_t cleanup patches etc. > > Benchmarks for local_t variants > > (This patch also fixes the x86 cpu_local_* macros, which are obviously > unused). > > I chose a large array (1M longs) for the inc/add/add_return tests so > the trivalue case would show some cache pressure. > > The cpu_local_inc case is always cache-hot, so it's not comparable to > the others. > > Time in ns per iteration (brackets is with CONFIG_PREEMPT=y): > > inc add add_return cpu_local_inc read > x86-32: 2.13 Ghz Core Duo 2 > atomic_long 118 118 115 17 17 > irqsave/rest 77 78 77 23 16 > trivalue 45 45 127 3(6) 21 > local_t 36 36 36 1(5) 17 > > x86-64: 2.6 GHz Dual-Core AMD Opteron 2218 > atomic_long 55 60 - 6 19 > irqsave/rest 54 54 - 11 19 > trivalue 47 47 - 5 28 > local_t 47 46 - 1 19 coolness! > > Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx> > --- > arch/x86/include/asm/local.h | 20 ++-- > init/main.c | 198 +++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 208 insertions(+), 10 deletions(-) it's a gem - but init/main.c is an arguably pretty sucky place for it. Stick it somewhere in lib/*, to be moved into testing/* later on? Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
