linux-ext4 - Re: [PATCH 07/10] libext2fs: use the rbtree bitmap by default when initializing a file system

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Message-ID: <alpine.LFD.2.00.1112191424580.30656@dhcp-27-109.brq.redhat.com>
Date:	Mon, 19 Dec 2011 15:15:31 +0100 (CET)
From:	Lukas Czerner <lczerner@...hat.com>
To:	"Theodore Ts'o" <tytso@....edu>
cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 07/10] libext2fs: use the rbtree bitmap by default when
 initializing a file system

On Sun, 18 Dec 2011, Theodore Ts'o wrote:

> This change causes the max resident memory of mke2fs, as reported by
> /usr/bin/time, to drop from 9296k to 5328k when formatting a 25
> gig volume.

Just for the record, creating bigger file system will show much bigger
difference. For example when creating 100T file system with the old
bitarray backend it will consume 14GB of memory, but with the new rbtree
backend it will only consume 220 MB (reported by /usr/bin/time).

Actually the real allocated memory according to valgrind is 54MB for
rbtree and 3.74GB for bitmap backend. I assume that /usr/bin/time shows
amount of dirtied memory pages ??

A while ago I have done some testing on older version of e2fsprogs with
rbtree patches. The numbers might differ now, but the overall difference
between rbtree and bitmaps should be roughly the same. Here are some
graphs:

http://people.redhat.com/lczerner/e2fsprogs_memory/graphs.pdf

Thanks!
-Lukas

> 
> Signed-off-by: "Theodore Ts'o" <tytso@....edu>
> ---
>  lib/ext2fs/initialize.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/lib/ext2fs/initialize.c b/lib/ext2fs/initialize.c
> index b050a0a..a63ea18 100644
> --- a/lib/ext2fs/initialize.c
> +++ b/lib/ext2fs/initialize.c
> @@ -112,6 +112,7 @@ errcode_t ext2fs_initialize(const char *name, int flags,
>  	fs->magic = EXT2_ET_MAGIC_EXT2FS_FILSYS;
>  	fs->flags = flags | EXT2_FLAG_RW;
>  	fs->umask = 022;
> +	fs->default_bitmap_type = EXT2FS_BMAP64_RBTREE;
>  #ifdef WORDS_BIGENDIAN
>  	fs->flags |= EXT2_FLAG_SWAP_BYTES;
>  #endif
> 
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