On 1 July 2013 22:46, Thomas Gleixner <t...@linutronix.de> wrote: > On Mon, 1 Jul 2013, James Hogan wrote: >> Use a completion to block until a secondary CPU has started up, like ARM >> do, instead of a loop of udelays. >> >> On Meta, SMP is really SMT, with each "CPU" being a different hardware >> thread on the same Meta processor core, so as well as being more >> efficient and latency friendly, using a completion prevents the bogomips >> of the secondary CPU from being drastically skewed every time by the >> execution of the tight in-cache udelay loop on the other CPU. > > The least of our worries is the correctness of bogomips. But if that > patch makes bogomips less bogus while fixing a real issue, please add > my > > Acked-by: Thomas Gleixner <t...@linutronix.de>
Yes, it's not so much the absolute value, but that secondary cpus will have a bogomips around 25% higher than the boot cpu, even though they should be about equal (ignoring the effects of other cpus). If I understand correctly, all else being equal this would make udelay block for a different amount of time on different cpus (although I haven't tried measuring it). James -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
