Sorry, this email slipped through the cracks. On Wed, Dec 06, 2017 at 05:06:35PM -0800, Andrew Morton wrote: > On Fri, 1 Dec 2017 13:57:50 +0000 Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > > > The memcg cpu_dead callback can be called early during startup > > (CONFIG_DEBUG_HOTPLUG_CPU0) with preemption enabled, which triggers a > > warning in its __this_cpu_xchg() calls. But CPU locality is always > > guaranteed, which is the only thing we really care about here. > > > > Using the preemption-safe this_cpu_xchg() addresses this problem. > > > > Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> > > --- > > > > Andrew, can you please merge this fixlet into the original patch? > > Did. > > I see that lkp-robot identified a performance regression and pointed > the finger at this patch? Right, it reports a perf drop in page fault stress tests, but that is to be the expected trade-off. Before, we'd do everything per cpu, and have to collapse all counters everytime somebody would read the stats. Now we fold them in batches, which introduces a periodic atomic when the batches are flushed (same frequency as we per-cpu cache charges for the atomic page_counter). -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
