On Thu, Aug 22, 2024 at 5:39 AM David Hildenbrand <david@xxxxxxxxxx> wrote: > > On 12.08.24 00:49, Barry Song wrote: > > From: Barry Song <v-songbaohua@xxxxxxxx> > > > > When an mTHP is added to the deferred_list, its partial pages > > are unused, leading to wasted memory and potentially increasing > > memory reclamation pressure. > > > > Detailing the specifics of how unmapping occurs is quite difficult > > and not that useful, so we adopt a simple approach: each time an > > mTHP enters the deferred_list, we increment the count by 1; whenever > > it leaves for any reason, we decrement the count by 1. > > > > Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx> > > --- > > Documentation/admin-guide/mm/transhuge.rst | 5 +++++ > > include/linux/huge_mm.h | 1 + > > mm/huge_memory.c | 6 ++++++ > > 3 files changed, 12 insertions(+) > > > > diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst > > index 9fdfb46e4560..7072469de8a8 100644 > > --- a/Documentation/admin-guide/mm/transhuge.rst > > +++ b/Documentation/admin-guide/mm/transhuge.rst > > @@ -532,6 +532,11 @@ nr_anon > > These huge pages could be entirely mapped or have partially > > unmapped/unused subpages. > > > > +nr_split_deferred > > + the number of anon huge pages which have been partially unmapped > > + and put onto split queue. Those unmapped subpages are also unused > > + and temporarily wasting memory. > > The name suggests something else ... like a counter of how many have > been deferred split :) > > Would "nr_anon_partially_mapped" "nr_anon_split_pending" (or something > less mouthful) be clearer? > > (likely "anon" really should be part of the name in any case) > > The name we chose (and the implied semantics) will likely have > implications on the handling of Usamas series. > Hi David, Your point is quite similar to my V1, though not exactly the same. I aimed to make the name more meaningful for users. https://lore.kernel.org/all/20240808010457.228753-3-21cnbao@xxxxxxxxx/ Ryan felt that the name should be consistent with the existing split_deferred. https://lore.kernel.org/all/36e8f1be-868d-4bce-8f32-e2d96b8b7af3@xxxxxxx/#t It seems that the existing split_deferred may now be less optimal with Usama's series, as entirely_mapped folios might also be on the list. Ryan is out right now, but I suppose he will be convinced that "nr_anon_partially_mapped" is probably a better name once he returns and reviews Usama's series. :-) > -- > Cheers, > > David / dhildenb > Thanks Barry
