Re: Btrfs v0.16 released

On Thu, 2008-08-14 at 23:17 +0200, Andi Kleen wrote:

On Thu, Aug 14, 2008 at 05:00:56PM -0400, Chris Mason wrote:

quoted

Btrfs defaults                  57.41 MB/s

Looks like I can get the btrfs defaults up to 64MB/s with some writeback
tweaks.

quoted

Btrfs dup no csum               74.59 MB/s 

With duplications checksums seem to be quite costly (CPU bound?)

The async worker threads should be spreading the load across CPUs pretty
well, and even a single CPU could keep up with 100MB/s checksumming.
But, the async worker threads do randomize the IO somewhat because the
IO goes from pdflush -> one worker thread per CPU -> submit_bio.  So,
maybe that 3rd thread is more than the drive can handle?

btrfsck tells me the total size of the btree is only 20MB larger with
checksumming on.

quoted

Btrfs no duplication            76.83 MB/s
Btrfs no dup no csum no inline  76.85 MB/s

But without duplication they are basically free here at least
in IO rate. Seems odd?

Does it compute them twice in the duplication case perhaps?

The duplication happens lower down in the stack, they only get done
once.

-chris