On Thu, Mar 08, 2012 at 12:20:26PM -0800, Boaz Harrosh wrote: > On 03/08/2012 10:09 AM, Chris Mason wrote: > > > > But, why are we writeback for a second or more? Aren't there other > > parts of this we would want to fix as well? > > > > I'm not against only turning on stable pages when they are needed, but > > the code that isn't the default tends to be somewhat less used. So it > > does increase testing burden when we do want stable pages, and it tends > > to make for awkward bugs that are hard to reproduce because someone > > neglects to mention it. > > > > IMHO it's much more important to nail down the 2 second writeback > > latency. That's not good. > > > > I think I understand this one. It's do to the sync nature introduced > by page_waiting in mkwrite. Pages go from dirty to writeback for a few reasons. Background writeout, or O_DIRECT or someone running sync background writeout shouldn't be queueing up so much work that synchronous writeout has a 2 second delay. If the latencies are coming from something that was run through fsync...well there's not too much we can do about that. The problem is that our page_mkwrite call isn't starting the IO it is just waiting on it, so we can't bump the priority on it. -chris -- 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
