linux-kernel - RE: [PATCH] maple_tree: Do not inline write slow path

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Message-ID: <040322fa455941ff9b82ebb0f53a576a@AcuMS.aculab.com>
Date:   Thu, 21 Jul 2022 08:26:34 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Liam Howlett' <liam.howlett@...cle.com>,
        "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>
CC:     Yu Zhao <yuzhao@...gle.com>
Subject: RE: [PATCH] maple_tree: Do not inline write slow path

From: Liam Howlett
> Sent: 21 July 2022 01:53
> 
> Having the slow path inlined causes too much stack usage.  Create new
> function mas_wr_bnode() to write a big node into the tree

Unless you mark the function 'noinline' the compiler is
likely to inline it anyway.

	David

> 
> Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> ---
>  lib/maple_tree.c | 22 +++++++++++++++++-----
>  1 file changed, 17 insertions(+), 5 deletions(-)
> 
> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> index 95d8659c5a99..4c383c780162 100644
> --- a/lib/maple_tree.c
> +++ b/lib/maple_tree.c
> @@ -4297,12 +4297,27 @@ static inline bool mas_wr_append(struct ma_wr_state *wr_mas)
>  	return false;
>  }
> 
> +/*
> + * mas_wr_bnode() - Slow path for a modification.
> + * @wr_mas: The write maple state
> + *
> + * This is where split, rebalance end up.
> + */
> +static void mas_wr_bnode(struct ma_wr_state *wr_mas)
> +{
> +	struct maple_big_node b_node;
> +
> +	trace_ma_write(__func__, wr_mas->mas, 0, wr_mas->entry);
> +	memset(&b_node, 0, sizeof(struct maple_big_node));
> +	mas_store_b_node(wr_mas, &b_node, wr_mas->offset_end);
> +	mas_commit_b_node(wr_mas, &b_node, wr_mas->node_end);
> +}
> +
>  static inline void mas_wr_modify(struct ma_wr_state *wr_mas)
>  {
>  	unsigned char node_slots;
>  	unsigned char node_size;
>  	struct ma_state *mas = wr_mas->mas;
> -	struct maple_big_node b_node;
> 
>  	/* Direct replacement */
>  	if (wr_mas->r_min == mas->index && wr_mas->r_max == mas->last) {
> @@ -4338,10 +4353,7 @@ static inline void mas_wr_modify(struct ma_wr_state *wr_mas)
>  		return;
> 
>  slow_path:
> -	memset(&b_node, 0, sizeof(struct maple_big_node));
> -	mas_store_b_node(wr_mas, &b_node, wr_mas->offset_end);
> -	trace_ma_write(__func__, mas, 0, wr_mas->entry);
> -	mas_commit_b_node(wr_mas, &b_node, wr_mas->node_end);
> +	mas_wr_bnode(wr_mas);
>  }
> 
>  /*
> --
> 2.35.1

-
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