On Fri, Dec 25, 2009 at 11:14:53AM -0500, tytso@xxxxxxx wrote: > On Thu, Dec 24, 2009 at 05:52:34PM -0800, Christian Kujau wrote: > > > > Well, I do "sync" after each operation, so the data should be on disk, but > > that doesn't mean it'll clear the filesystem buffers - but this doesn't > > happen that often in the real world too. Also, all filesystem were tested > > equally (I hope), yet some filesystem perform better than another - even > > if all the content copied/tar'ed/removed would perfectly well fit into the > > machines RAM. > > Did you include the "sync" in part of what you timed? Peter was quite > right --- the fact that the measured bandwidth in your "cp" test is > five times faster than the disk bandwidth as measured by hdparm, and > many file systems had exactly the same bandwidth, makes me very > suspicious that what was being measured was primarily memory bandwidth > --- and not very useful when trying to measure file system > performance. Dudes, sync() doesn't flush the fs cache, you have to unmount for that. Once upon a time Linux had an ioctl() to flush the fs buffers, I used it in lmbench. ioctl(fd, BLKFLSBUF, 0); No idea if that is still supported, but sync() is a joke for benchmarking. -- --- Larry McVoy lm at bitmover.com http://www.bitkeeper.com -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
