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Date:   Sun, 26 Jan 2020 21:56:01 -0500
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Li Dongyang <dongyangli@....com>
Cc:     "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
        "adilger@...ger.ca" <adilger@...ger.ca>
Subject: Re: [PATCH v3 1/5] libext2fs: optimize
 ext2fs_convert_subcluster_bitmap()

On Wed, Nov 20, 2019 at 04:35:21AM +0000, Li Dongyang wrote:
> For a bigalloc filesystem, converting the block bitmap from blocks
> to chunks in ext2fs_convert_subcluster_bitmap() can take a long time
> when the device is huge, because we test the bitmap
> bit-by-bit using ext2fs_test_block_bitmap2().
> Use ext2fs_find_first_set_block_bitmap2() which is more efficient
> for mke2fs when the fs is mostly empty.
> 
> e2fsck can also benefit from this during pass1 block scanning.
> 
> Time taken for "mke2fs -O bigalloc,extent -C 131072 -b 4096" on a 1PB
> device:
> 
> without patch:
> real    27m49.457s
> user    21m36.474s
> sys     6m9.514s
> 
> with patch:
> real    6m31.908s
> user    0m1.806s
> sys    6m29.697s
> 
> Signed-off-by: Li Dongyang <dongyangli@....com>
> Reviewed-by: Andreas Dilger <adilger@...ger.ca>

Applied, thanks.

					- Ted

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