Theodore Tso wrote:
On Thu, Jul 10, 2008 at 11:14:28AM -0500, Eric Sandeen wrote:
Val & I talked about this a little, and came to the conclusion that
directory fragmentation might be a pretty big part of it.
Hmm, could be. Let's see. Ric said 46.5 million files, I don't know
how big the filenames were, but let's assume a directory entry size of
32, so that means if we assume perfect packing, 128 directory entries
per 4k block. Let's use 100 directory entries/blok just to make the
math easyer, so that's 465,000 blocks. If we assume a 10ms seek time,
and that the blocks are totally scattered, that's 4650 seconds, or
1.29 hours. So that's roughly within the ballpark that Ric measured.
- Ted
(changing cc to the real list instead of ext4 owner - sorry!)
The file names are 40 bytes long, (6 initial bytes of time stamp with 24
random bytes at end of name. For example:
451aeb61ead89~~~DYASX8LYL4NAUWK3WI187VRP
The 4 threads chose the target subdirectory based on the time stamp,
rotating into a new subdirectory every 3 minutes or so.
ric
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
