On Mon, Apr 01, 2013 at 10:18:51AM -0500, Eric Sandeen wrote: > I'd add: > > 3) Why do we have a "nodelalloc" mount option at all? > > but then I thought: > > Is it also this bad when using the ext4 driver to run an ext3 fs? Yes, and I there would be a similar performance problem if you are using the ext3 file system driver, since ext3_*_writepage() also ends up calling block_write_full_page() which will also result in the writes happening with WRITE_SYNC. The main reason why we keep nodelalloc at this point is bug-for-bug compatibility with ext3 file systems --- basically, for users who are using this as a workaround for the O_PONIES issue instead of fixing their applications to use fsync() appropriately. So another question is how much do we care about exact emulation of ext3's behaviour for those distributions who wish to use ext4 file system driver for ext2 and ext3 file systems? One of the reasons for keeping nodealloc mode was the argument was that it removing it wouldn't really allow us to remove that much complexity from ext4. But adding a nodealloc specific ext4_writepages pages would result in adding a huge amount of complexity, and my first reaction is that it's really not worth the code maintenance headache. Dmitry, is there a reason why you are especially worried about the performace of nodelalloc mode? - Ted -- 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
