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Date: Fri, 15 Aug 2008 03:39:34 +0200 From: Andi Kleen <andi@...stfloor.org> To: Chris Mason <chris.mason@...cle.com> Cc: Andi Kleen <andi@...stfloor.org>, Peter Zijlstra <peterz@...radead.org>, linux-btrfs <linux-btrfs@...r.kernel.org>, linux-kernel <linux-kernel@...r.kernel.org>, linux-fsdevel <linux-fsdevel@...r.kernel.org> Subject: Re: Btrfs v0.16 released > 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? You have more threads with duplication? > > 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. Ok was just speculation. The big difference still seems odd. -Andi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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