On Wed, Apr 19, 2017 at 05:52:39PM +1000, Balbir Singh wrote:
In this patch we create N_COHERENT_MEMORY, which is different
from N_MEMORY. A node hotplugged as coherent memory will have
this state set. The expectation then is that this memory gets
onlined like regular nodes. Memory allocation from such nodes
occurs only when the the node is contained explicitly in the
mask.
Finally got around to test drive this. From what I can see, as expected,
both kernel and userspace seem to ignore these nodes, unless you
allocate specifically from them. Very convenient.
Is "online_coherent"/MMOP_ONLINE_COHERENT the right way to trigger this?
That mechanism is used to specify zone, and only for a single block of
memory. This concept applies to the node as a whole. I think it should
be independent of memory onlining.
I mean, let's say online_kernel N blocks, some of them get allocated,
and then you online_coherent block N+1, flipping the entire node into
N_COHERENT_MEMORY. That doesn't seem right.
That said, this set as it stands needs an adjustment when based on top
of Michal's onlining revamp [1]. As-is, allow_online_pfn_range() is
returning false. The patch below fixed it for me.
[1] http://lkml.kernel.org/r/20170421120512.23960-1-mhocko@xxxxxxxxxx
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 4a535f1..ccb7a84 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -869,16 +869,20 @@ bool allow_online_pfn_range(int nid, unsigned long pfn, unsigned long nr_pages,
* though so let's stick with it for simplicity for now.
* TODO make sure we do not overlap with ZONE_DEVICE
*/
- if (online_type == MMOP_ONLINE_KERNEL) {
+ switch (online_type) {
+ case MMOP_ONLINE_KERNEL:
if (zone_is_empty(movable_zone))
return true;
return movable_zone->zone_start_pfn >= pfn + nr_pages;
- } else if (online_type == MMOP_ONLINE_MOVABLE) {
+ case MMOP_ONLINE_MOVABLE:
return zone_end_pfn(normal_zone) <= pfn;
+ case MMOP_ONLINE_KEEP:
+ case MMOP_ONLINE_COHERENT:
+ /* These will always succeed and inherit the current zone */
+ return true;
}
- /* MMOP_ONLINE_KEEP will always succeed and inherits the current zone */
- return online_type == MMOP_ONLINE_KEEP;
+ return false;
}
static void __meminit resize_zone_range(struct zone *zone, unsigned long start_pfn,
--
Reza Arbab
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