Messages in this thread | | | Subject | Re: Btrfs v0.16 released | From | Chris Mason <> | Date | Thu, 14 Aug 2008 21:25:54 -0400 |
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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
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