Re: bad O_DIRECT read and write performance with small block sizes with virtio

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 On 08/03/2010 05:40 PM, John Leach wrote:

dd if=/dev/mapper/zero of=/dev/null bs=8k count=1000000 iflag=direct
8192000000 bytes (8.2 GB) copied, 3.46529 s, 2.4 GB/s

dd if=/dev/mapper/zero of=/dev/null bs=8k count=1000000
8192000000 bytes (8.2 GB) copied, 5.5741 s, 1.5 GB/s

dd is just using read.


What's /dev/mapper/zero?  A real volume or a zero target?

--
error compiling committee.c: too many arguments to function

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