Am 09.02.21 um 18:33 schrieb Suren Baghdasaryan:
On Tue, Feb 9, 2021 at 4:57 AM Christian König <christian.koenig@xxxxxxx> wrote:
Am 09.02.21 um 13:11 schrieb Christian König:
[SNIP]
+void drm_page_pool_add(struct drm_page_pool *pool, struct page *page)
+{
+ spin_lock(&pool->lock);
+ list_add_tail(&page->lru, &pool->items);
+ pool->count++;
+ atomic_long_add(1 << pool->order, &total_pages);
+ spin_unlock(&pool->lock);
+
+ mod_node_page_state(page_pgdat(page),
NR_KERNEL_MISC_RECLAIMABLE,
+ 1 << pool->order);
Hui what? What should that be good for?
This is a carryover from the ION page pool implementation:
https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Ftree%2Fdrivers%2Fstaging%2Fandroid%2Fion%2Fion_page_pool.c%3Fh%3Dv5.10%23n28&data=04%7C01%7Cchristian.koenig%40amd.com%7Cdccccff8edcd4d147a5b08d8cd20cff2%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637484888114923580%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=9%2BIBC0tezSV6Ci4S3kWfW%2BQvJm4mdunn3dF6C0kyfCw%3D&reserved=0
My sense is it helps with the vmstat/meminfo accounting so folks can
see the cached pages are shrinkable/freeable. This maybe falls under
other dmabuf accounting/stats discussions, so I'm happy to remove it
for now, or let the drivers using the shared page pool logic handle
the accounting themselves?
Intentionally separated the discussion for that here.
As far as I can see this is just bluntly incorrect.
Either the page is reclaimable or it is part of our pool and freeable
through the shrinker, but never ever both.
IIRC the original motivation for counting ION pooled pages as
reclaimable was to include them into /proc/meminfo's MemAvailable
calculations. NR_KERNEL_MISC_RECLAIMABLE defined as "reclaimable
non-slab kernel pages" seems like a good place to account for them but
I might be wrong.
Yeah, that's what I see here as well. But exactly that is utterly nonsense.
Those pages are not "free" in the sense that get_free_page could return
them directly.
Regards,
Christian.
In the best case this just messes up the accounting, in the worst case
it can cause memory corruption.
Christian.
