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: > > Btrfs defaults 57.41 MB/s Looks like I can get the btrfs defaults up to 64MB/s with some writeback tweaks. > > 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. > > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
