On 4/21/2010 11:36 AM, malahal@us.ibm.com wrote: > Interesting! You are doing direct I/O to avoid copying from cache to user > buffer for read and vice-versa for write, but you are losing the ability > to do them parallel! You are doing the next best, that is creating two > "dd" threads -- one for reading and another for writing. Since the pipe > is really implemented in memory, why should this be faster than normal > "dd" that uses page cache? Likely that kswapd is not kicking early > enough? Oops, my eyes missed the pipe and second dd when I made my previous comments. That is pretty good for different disks then yes... not so good for same physical disk. > Enhancing "dd" to create a reader and a writer thread would really > help, I believe. I actually have some old hacked up dd code I made once to use 16 concurrent aio requests with O_DIRECT. I need to clean it up a bit but it showed great promise. _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
