On Mon, 2012-07-30 at 11:40 +0930, Rusty Russell wrote: > We still patch SMP instructions to UP variants if we boot with a > single CPU, but not at any other time. In particular, not if we > unplug CPUs to return to a single cpu. > > Paul McKenney points out: > > mean offline overhead is 6251/48=130.2 milliseconds. > > If I remove the alternatives_smp_switch() from the offline > path [...] the mean offline overhead is 550/42=13.1 milliseconds > > Basically, we're never going to get those 120ms back, and the code is > pretty messy. > > We get rid of: > 1) The "smp-alt-once" boot option. It's actually "smp-alt-boot", the > documentation is wrong. It's now the default. > 2) The skip_smp_alternatives flag used by suspend. > 3) arch_disable_nonboot_cpus_begin() and arch_disable_nonboot_cpus_end() > which were only used to set this one flag. > > Signed-off-by: Rusty Russell <[email protected]>
Acked-by: Suresh Siddha <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
