On Thu, Apr 28, 2011 at 10:05:09AM -0500, Christoph Lameter wrote: > On Thu, 28 Apr 2011, Tejun Heo wrote: > > Gees, Christoph. That is a test case to show the issue prominently, > > which is what a test case is supposed to do. What it means is that > > _any_ update can trigger @batch deviation on _sum() regardless of its > > frequency or concurrency level and that's the nastiness I've been > > talking about over and over again. > > As far as I understand it: This is a test case where you want to show us > the atomic_t type behavior of _sum. This only works in such an artificial > test case. In reality batches of updates will modify any 'accurate' result > that you may have obtained from the _sum function. It seems like we can split hairs all day long about the similarities and differences with atomics, so let's forget about atomics for now. I don't like any update having possibility of causing @batch jumps in _sum() result. That severely limits the usefulness of hugely expensive _sum() and the ability to scale @batch. Not everything in the world is vmstat. Think about other _CURRENT_ use cases in filesystems. -- tejun -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>