Re: [PATCH] btrfs-progs: eliminate some unnecessary btrfs_lookup_extent_info() calls in walk_down_tree()

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On Tue, Aug 16, 2016 at 02:17:57PM +0800, Wang Xiaoguang wrote:
> In walk_down_tree(), we may call btrfs_lookup_extent_info() for same tree
> block many times, obviously unnecessary. Here we define a simple struct to
> record whether we already have gotten tree block's refs:
>         struct node_refs {
>                 u64 bytenr[BTRFS_MAX_LEVEL];
>                 u64 refs[BTRFS_MAX_LEVEL];
>         };
> 
> I fill a disk partition with linux kernel source codes and use below
> test script to have performance test.
> 	#!/bin/bash
> 
> 	echo 3 > /proc/sys/vm/drop_caches
> 	for ((i = 0; i < 20; i++)); do
> 		time ./btrfsck  /dev/sdc5
> 	done 2>&1 | grep real | awk -F "[ms]" '{run_time += $2} END{print run_time / 20}'
> 
> Before this patch, it averagely took 0.8447s for every btrfsck execution,
> and with this patch, it averagely took 0.7807s.
> 
> Signed-off-by: Wang Xiaoguang <wangxg.fnst@xxxxxxxxxxxxxx>

Applied, thanks.
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