On Wednesday 23 March 2005 18:09, Bodo Stroesser wrote:
blaisorblade@xxxxxxxx wrote:
Use rep_nop instead of barrier for cpu_relax, following $(SUBARCH)'s
doing that (i.e. i386 and x86_64).
IIRC, Jeff had the idea, to use sched_yield() for this (from a discussion
on #uml).
Hmm, makes sense, but this is to benchmark well... I remember from early discussions on 2.6 scheduler that using sched_yield might decrease performance (IIRC starve the calling application).
Also, that call should be put inside the idle loop, not for cpu_relax, which is very different, since it is used (for instance) in kernel/spinlock.c for spinlocks, and in such things. The "Pause" opcode is explicitly recommended (by Intel manuals, I don't recall why) for things like spinlock loops, and using yield there would be bad.