On 13.07.23 17:40, Verma, Vishal L wrote:
On Thu, 2023-07-13 at 17:23 +0200, David Hildenbrand wrote:
On 13.07.23 17:15, Verma, Vishal L wrote:
On Thu, 2023-07-13 at 09:23 +0200, David Hildenbrand wrote:
On 13.07.23 08:45, Verma, Vishal L wrote:
I'm taking a shot at implementing the splitting internally in
memory_hotplug.c. The caller (kmem) side does become trivial with this
approach, but there's a slight complication if I don't have the module
param override (patch 1 of this series).
The kmem diff now looks like:
diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
index 898ca9505754..8be932f63f90 100644
--- a/drivers/dax/kmem.c
+++ b/drivers/dax/kmem.c
@@ -105,6 +105,8 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
data->mgid = rc;
for (i = 0; i < dev_dax->nr_range; i++) {
+ mhp_t mhp_flags = MHP_NID_IS_MGID | MHP_MEMMAP_ON_MEMORY |
+ MHP_SPLIT_MEMBLOCKS;
struct resource *res;
struct range range;
@@ -141,7 +143,7 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
* this as RAM automatically.
*/
rc = add_memory_driver_managed(data->mgid, range.start,
- range_len(&range), kmem_name, MHP_NID_IS_MGID);
+ range_len(&range), kmem_name, mhp_flags);
if (rc) {
dev_warn(dev, "mapping%d: %#llx-%#llx memory add failed\n",
Why do we need the MHP_SPLIT_MEMBLOCKS?
I thought we still wanted either an opt-in or opt-out for the kmem
driver to be able to do memmap_on_memory, in case there were
performance implications or the lack of 1GiB PUDs. I haven't
implemented that yet, but I was thinking along the lines of a sysfs
knob exposed by kmem, that controls setting of this new
MHP_SPLIT_MEMBLOCKS flag.
Why is MHP_MEMMAP_ON_MEMORY not sufficient for that?
Ah I see what you mean now - knob just controls MHP_MEMMAP_ON_MEMORY,
and memory_hotplug is free to split to memblocks if it needs to to
satisfy that.
And if you don't want memmap holes in a larger area you're adding (for
example to runtime-allocate 1 GiB pages), simply check the size your
adding, and if it's, say, less than 1 G, don't set the flag.
But that's probably a corner case use case not worth considering for now.
That sounds reasonable. Let me give this a try and see if I run into
anything else. Thanks David!
Sure!
--
Cheers,
David / dhildenb
