linux-ext4 - Re: [PATCH] ext4: reuse order and buddy in mb_mark

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Date:   Tue, 21 Jun 2022 10:40:30 +0800
From:   hanjinke <hanjinke.666@...edance.com>
To:     tytso@....edu, adilger.kernel@...ger.ca
Cc:     linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        lei.rao@...el.com
Subject: Re: [PATCH] ext4: reuse order and buddy in mb_mark_used when buddy
 split

hi, friendly pinging...

在 2022/6/6 下午11:53, Jinke Han 写道:
> From: hanjinke <hanjinke.666@...edance.com>
> 
> After each buddy split, mb_mark_used will search the proper order
> for the block which may consume some loop in mb_find_order_for_block.
> In fact, we can reuse the oder and buddy generated by the buddy split.
> 
> Reviewed by: lei.rao@...el.com
> Signed-off-by: hanjinke <hanjinke.666@...edance.com>
> ---
>   fs/ext4/mballoc.c | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 9f12f29bc346..c7ac6b269dd8 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -1933,6 +1933,7 @@ static int mb_mark_used(struct ext4_buddy *e4b, struct ext4_free_extent *ex)
>   	unsigned ret = 0;
>   	int len0 = len;
>   	void *buddy;
> +	bool split = false;
>   
>   	BUG_ON(start + len > (e4b->bd_sb->s_blocksize << 3));
>   	BUG_ON(e4b->bd_group != ex->fe_group);
> @@ -1957,12 +1958,16 @@ static int mb_mark_used(struct ext4_buddy *e4b, struct ext4_free_extent *ex)
>   
>   	/* let's maintain buddy itself */
>   	while (len) {
> -		ord = mb_find_order_for_block(e4b, start);
> +		if (!split)
> +			ord = mb_find_order_for_block(e4b, start);
>   
>   		if (((start >> ord) << ord) == start && len >= (1 << ord)) {
>   			/* the whole chunk may be allocated at once! */
>   			mlen = 1 << ord;
> -			buddy = mb_find_buddy(e4b, ord, &max);
> +			if (!split)
> +				buddy = mb_find_buddy(e4b, ord, &max);
> +			else
> +				split = false;
>   			BUG_ON((start >> ord) >= max);
>   			mb_set_bit(start >> ord, buddy);
>   			e4b->bd_info->bb_counters[ord]--;
> @@ -1989,6 +1994,7 @@ static int mb_mark_used(struct ext4_buddy *e4b, struct ext4_free_extent *ex)
>   		mb_clear_bit(cur + 1, buddy);
>   		e4b->bd_info->bb_counters[ord]++;
>   		e4b->bd_info->bb_counters[ord]++;
> +		split = true;
>   	}
>   	mb_set_largest_free_order(e4b->bd_sb, e4b->bd_info);
>