On 04/09/15 17:04, Yury Norov wrote:
This patch is on top of https://lkml.org/lkml/2015/9/2/413In master, there's only a single function - update_mixed_endian_el0_support And similar function is on review mentioned above. The algorithm for them is like this: - there's system-wide boolean marker for the feature that is initially enabled; - there's also updater for the feature that may disable it system-widely if feature is not supported on current CPU. - updater is called for each CPU on bootup. The problem is the way updater does its work. On each CPU, it unconditionally updates system-wide marker. For multi-core system it makes CPU issue invalidate message for a cache line containing marker. This invalidate increases cache contention for nothing, because there's a single marker reset that is really needed, and the others are useless. If the number of system-wide markers of this sort will grow, it may become a trouble on large-scale SOCs. The fix is trivial, though: do system-wide marker update conditionally, and preserve corresponding cache line in shared state for all update() calls, except, probably, one.
As I have mentioned already, this patch (and the per feature functions) won't be needed once we merge my series (which is waiting for the merge window to see the public lights) Cheers Suzuki -- 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/
