On Mon, Sep 23, 2019 at 05:47:24PM +0200, David Hildenbrand wrote:

On 23.09.19 17:45, David Hildenbrand wrote:

quoted

On 23.09.19 17:37, Michael S. Tsirkin wrote:

quoted

On Mon, Sep 23, 2019 at 08:28:00AM -0700, Alexander Duyck wrote:

quoted

On Mon, Sep 23, 2019 at 8:00 AM Michael S. Tsirkin [off-list ref] wrote:

quoted

On Mon, Sep 23, 2019 at 07:50:15AM -0700, Alexander Duyck wrote:

quoted

quoted

quoted

+static inline void
+page_reporting_reset_boundary(struct zone *zone, unsigned int order, int mt)
+{
+     int index;
+
+     if (order < PAGE_REPORTING_MIN_ORDER)
+             return;
+     if (!test_bit(ZONE_PAGE_REPORTING_ACTIVE, &zone->flags))
+             return;
+
+     index = get_reporting_index(order, mt);
+     reported_boundary[index] = &zone->free_area[order].free_list[mt];
+}

So this seems to be costly.
I'm guessing it's the access to flags:


        /* zone flags, see below */
        unsigned long           flags;

        /* Primarily protects free_area */
        spinlock_t              lock;



which is in the same cache line as the lock.

I'm not sure what you mean by this being costly?

I've just been wondering why does will it scale report a 1.5% regression
with this patch.

Are you talking about data you have collected from a test you have
run, or the data I have run?

About the kernel test robot auto report that was sent recently.

https://lkml.org/lkml/2019/9/21/112

And if I'm correct, that regression is observable in case reporting is
not enabled. (so with this patch applied only, e.g., on a bare-metal system)

To be even more precise: # CONFIG_PAGE_REPORTING is not set

Even if it was, I'd hope for 0 overhead when not present runtime.

-- 
MST

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel