Commit 17983dc6 authored by Liam R. Howlett's avatar Liam R. Howlett Committed by Andrew Morton
Browse files

maple_tree: refine mas_preallocate() node calculations 

Calculate the number of nodes based on the pending write action instead
of assuming the worst case.

This addresses a performance regression introduced in platforms that
have longer allocation timing.

Link: https://lkml.kernel.org/r/20230724183157.3939892-14-Liam.Howlett@oracle.com


Signed-off-by: default avatarLiam R. Howlett <Liam.Howlett@oracle.com>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 0b8bb544

lib/maple_tree.c

+43 −1
Original line number Diff line number Diff line
@@ -5535,9 +5535,51 @@ EXPORT_SYMBOL_GPL(mas_store_prealloc); 
 */

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;



	mas_node_count_gfp(mas, 1 + mas_mt_height(mas) * 3, gfp);



	if (unlikely(!mas->index && mas->last == ULONG_MAX))

		goto ask_now;



	mas_wr_store_setup(&wr_mas);

	wr_mas.content = mas_start(mas);

	/* Root expand */

	if (unlikely(mas_is_none(mas) || mas_is_ptr(mas)))

		goto ask_now;



	if (unlikely(!mas_wr_walk(&wr_mas))) {

		/* Spanning store, use worst case for now */

		request = 1 + mas_mt_height(mas) * 3;

		goto ask_now;

	}



	/* At this point, we are at the leaf node that needs to be altered. */

	/* Exact fit, no nodes needed. */

	if (wr_mas.r_min == mas->index && wr_mas.r_max == mas->last)

		return 0;



	mas_wr_end_piv(&wr_mas);

	node_size = mas_wr_new_end(&wr_mas);

	if (node_size >= mt_slots[wr_mas.type]) {

		/* Split, worst case for now. */

		request = 1 + mas_mt_height(mas) * 2;

		goto ask_now;

	}



	/* New root needs a singe node */

	if (unlikely(mte_is_root(mas->node)))

		goto ask_now;



	/* Potential spanning rebalance collapsing a node, use worst-case */

	if (node_size  - 1 <= mt_min_slots[wr_mas.type])

		request = mas_mt_height(mas) * 2 - 1;



	/* node store, slot store needs one node */

ask_now:

	mas_node_count_gfp(mas, request, gfp);

	mas->mas_flags |= MA_STATE_PREALLOC;

	if (likely(!mas_is_err(mas)))

		return 0;