On Fri, Jul 12, 2013 at 10:44:21AM +1000, Dave Chinner wrote: > On Thu, Jul 11, 2013 at 12:02:18AM +0200, Jan Kara wrote: > > From: Christoph Hellwig <hch@xxxxxxxxxxxxx> > > > > Add support to the core direct-io code to defer AIO completions to user > > context using a workqueue. This replaces opencoded and less efficient > > code in XFS and ext4 and will be needed to properly support O_(D)SYNC > > for AIO. > > I don't see how this is any more efficient than the deferral > that XFS already does for direct IO completion - it just changes > what queues IO for completions. And on that topic: It avoided a memory allocation for each dіrect I/O write. > FWIW, in XFS we queue unwritten extent conversion completions on a > different workqueue to EOF size update completions because the > latter are small, fast and rarely require IO or get blocked. The > data IO completion workqueue for EOF updates has the same > concurrency and depth as the unwritten extent work queue (i.e. 256 > workers per cpu per superblock). So pushing all of this DIO and EOF > completion work into a single threaded global workqueue that can > block in every IO completion doesn't seem like a very smart idea to > me... Currently the direct I/O code doesn't support async extending writes. -- 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
