On Fri, Feb 19, 2016 at 05:49:32PM +1100, Dave Chinner wrote: > That doesn't really seem right. The writeback should be done as a > single ioend, with a single completion, with a single setsize > transaction, adn then all the pages are marked clean sequentially. > The above behaviour implies we are ending up doing something like: > > fsync proc io completion > wait on page 0 > end page 0 writeback > wake up page 0 > wait on page 1 > end page 1 writeback > wake up page 1 > wait on page 2 > end page 2 writeback > wake up page 2 > > Though in slightly larger batches than a single page (10 wakeups a > file, so batches of around 100 pages per wakeup?). i.e. the fsync > IO wait appears to be racing with IO completion marking pages as > done. I simply cannot see how the above change would cause that, as > it was simply a change in the IO submission code that doesn't affect > overall size or shape of the IOs being submitted.
Could this be the lack of blk plugs, which will cause us to complete too early?
