On 03/08/2012 12:37 PM, Chris Mason wrote: > 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. > I agree. I think the logger model is: write, than sync Before they used to be waiting on the sync phase now their waiting on write, when concurrent with sync. I would like to inspect this situation. I agree with you that it's just shifting heaviness that is now hiding somewhere else. > -chris Thanks Boaz -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
