On Wed, Dec 22, 2010 at 12:39:15PM -0800, Andy Isaacson wrote: > On Tue, Dec 21, 2010 at 03:07:33AM +0200, Felipe Contreras wrote: > > On Tue, Dec 21, 2010 at 12:24 AM, Andy Isaacson <adi@xxxxxxxxxxxxx> wrote: > > > I have a directory with 1.2M files in it, which makes readdir very slow > > > on btrfs with cold caches (although it's reasonably fast with hot caches > > > as in the first example below): > > > > Sounds like: > > > > Bug 21562 - btrfs is dead slow due to fragmentation > > https://bugzilla.kernel.org/show_bug.cgi?id=21562 > > Hmmm, how do I look at the btree layout for a given inode? There's documentation on the tree structures at [1] and [2]. If you know the inode number of the object you're interested in, you need to look in the FS tree for the subvolume it's in and find the (inode_number, EXTENT_DATA, ...) keys for the file. Each of those records will reference an individual disk extent -- and you can get the disk start position and length of the extent from the data stored under the key. Hugo. [1] https://btrfs.wiki.kernel.org/index.php/Btree_Items [2] https://btrfs.wiki.kernel.org/index.php/Data_Structures -- === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk === PGP key: 515C238D from wwwkeys.eu.pgp.net or http://www.carfax.org.uk --- Hail and greetings. We are a flat-pack invasion force from --- Planet Ikea. We come in pieces.
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