On 9/27/25 03:17, Suren Baghdasaryan wrote:
> On Wed, Sep 10, 2025 at 1:01 AM Vlastimil Babka <[email protected]> wrote:
>>
>> From: "Liam R. Howlett" <[email protected]>
>>
>> The fast path through a write will require replacing a single node in
>> the tree. Using a sheaf (32 nodes) is too heavy for the fast path, so
>> special case the node store operation by just allocating one node in the
>> maple state.
>>
>> Signed-off-by: Liam R. Howlett <[email protected]>
>> Signed-off-by: Vlastimil Babka <[email protected]>
>> ---
>> include/linux/maple_tree.h | 4 +++-
>> lib/maple_tree.c | 47
>> +++++++++++++++++++++++++++++++++++-----
>> tools/testing/radix-tree/maple.c | 9 ++++++--
>> 3 files changed, 51 insertions(+), 9 deletions(-)
>>
>> diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h
>> index
>> 166fd67e00d882b1e6de1f80c1b590bba7497cd3..562a1e9e5132b5b1fa8f8402a7cadd8abb65e323
>> 100644
>> --- a/include/linux/maple_tree.h
>> +++ b/include/linux/maple_tree.h
>> @@ -443,6 +443,7 @@ struct ma_state {
>> unsigned long min; /* The minimum index of this node -
>> implied pivot min */
>> unsigned long max; /* The maximum index of this node -
>> implied pivot max */
>> struct slab_sheaf *sheaf; /* Allocated nodes for this
>> operation */
>> + struct maple_node *alloc; /* allocated nodes */
Replacing with: /* A single allocated node for fast path writes */
since I'm touching it anyway due to previous patch fixup.
>>
>> @@ -1093,9 +1100,34 @@ static inline struct maple_node *mas_pop_node(struct
>> ma_state *mas)
>> */
>> static inline void mas_alloc_nodes(struct ma_state *mas, gfp_t gfp)
>> {
>> - if (unlikely(mas->sheaf)) {
>> - unsigned long refill = mas->node_request;
>> + if (!mas->node_request)
>> + return;
>> +
>> + if (mas->node_request == 1) {
>> + if (mas->sheaf)
>> + goto use_sheaf;
>
> Hmm, I don't get the above logic. One node is requested and instead of
> using possibly available mas->alloc, we jump to using mas->sheaf and
> freeing mas->alloc... That does not sound efficient. What am I
> missing?
I'm not changing it now due to merge window, only cosmetic changes and r-b
tags. Can leave it to a follow-up optimization.
