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FROMLIST: BACKPORT: maple_tree: Refine mas_preallocate() node calculations

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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.

Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>

Link: https://lore.kernel.org/lkml/20230601021605.2823123-14-Liam.Howlett@oracle.com/
[surenb: adjust node_size calculation, allow to store a slot when
possible]

Bug: 274059236
Change-Id: I1db402fb463ee1e391081d2d81c34619f15713ac
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
This commit is contained in:
Liam R. Howlett 2023-05-31 22:16:04 -04:00 committed by Suren Baghdasaryan
parent ce9ebd83aa
commit 133fbad5bd
1 changed files with 47 additions and 1 deletions
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48
lib/maple_tree.c
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@ -5810,9 +5810,55 @@ 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_node_size(&wr_mas);
if (node_size >= mt_slots[wr_mas.type]) {
/* Slot store is possible in some cases */
if ((node_size == mt_slots[wr_mas.type]) &&
(wr_mas.r_min == mas->index || wr_mas.r_max == mas->last))
goto ask_now;
/* 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;