[PATCH RFC v3 9/9] maple_tree: replace preallocation with slub percpu array prefill

From: Vlastimil Babka
Date: Wed Nov 29 2023 - 05:34:46 EST


With the percpu array we can try not doing the preallocations in maple
tree, and instead make sure the percpu array is prefilled, and using
GFP_ATOMIC in places that relied on the preallocation (in case we miss
or fail trylock on the array), i.e. mas_store_prealloc(). For now simply
add __GFP_NOFAIL there as well.
---
lib/maple_tree.c | 17 ++++++-----------
1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index f5c0bca2c5d7..d84a0c0fe83b 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -5452,7 +5452,12 @@ void mas_store_prealloc(struct ma_state *mas, void *entry)

mas_wr_store_setup(&wr_mas);
trace_ma_write(__func__, mas, 0, entry);
+
+retry:
mas_wr_store_entry(&wr_mas);
+ if (unlikely(mas_nomem(mas, GFP_ATOMIC | __GFP_NOFAIL)))
+ goto retry;
+
MAS_WR_BUG_ON(&wr_mas, mas_is_err(mas));
mas_destroy(mas);
}
@@ -5471,8 +5476,6 @@ int mas_preallocate(struct ma_state *mas, void *entry, gfp_t gfp)
MA_WR_STATE(wr_mas, mas, entry);
unsigned char node_size;
int request = 1;
- int ret;
-

if (unlikely(!mas->index && mas->last == ULONG_MAX))
goto ask_now;
@@ -5512,16 +5515,8 @@ int mas_preallocate(struct ma_state *mas, void *entry, gfp_t gfp)

/* node store, slot store needs one node */
ask_now:
- mas_node_count_gfp(mas, request, gfp);
- if (likely(!mas_is_err(mas)))
- return 0;
+ return kmem_cache_prefill_percpu_array(maple_node_cache, request, gfp);

- mas_set_alloc_req(mas, 0);
- ret = xa_err(mas->node);
- mas_reset(mas);
- mas_destroy(mas);
- mas_reset(mas);
- return ret;
}
EXPORT_SYMBOL_GPL(mas_preallocate);


--
2.43.0