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Date: Wed, 14 Jul 2010 04:39:35 +0200 From: Giangiacomo Mariotti <gg.mariotti@...il.com> To: Avi Kivity <avi@...hat.com> Cc: linux-kernel@...r.kernel.org Subject: Re: BTRFS: Unbelievably slow with kvm/qemu On Tue, Jul 13, 2010 at 6:29 AM, Avi Kivity <avi@...hat.com> wrote: > Btrfs is very slow on sync writes: > > 45KB/s, while 4-5MB/s traffic was actually going to the disk. For every 4KB > that the the application writes, 400KB+ of metadata is written. > > (It's actually worse, since it starts faster than the average and ends up > slower than the average). > > For kvm, you can try cache=writeback or cache=unsafe and get better > performance (though still slower than ext*). > Yeah, well I've already moved the virtual hd file to an ext3 partition, so the problem for me was actually already "solved" before posting the first post. I posted the first message just to report the particularly bad performances of Btrfs for this test-case, so that, if not already known, they could be investigated and hopefully solved. By the way, thanks to everyone who answered! -- Giangiacomo -- 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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