On Thu, Jul 14, 2016 at 07:35:05AM -0400, Tejun Heo wrote: > Hello, > > On Wed, Jul 13, 2016 at 04:04:04PM -0700, Paul E. McKenney wrote: > > commit b4edebb8f5664a3a51be1e3ff3d7f1cb2d3d5c88 > > Author: Paul E. McKenney <[email protected]> > > Date: Wed Jul 13 15:13:31 2016 -0700 > > > > rcu: Provide RCUSYNC_EXPEDITE option for rcusync.expedited default > > > > This commit provides an RCUSYNC_EXPEDITE Kconfig option that specifies > > the default value for the rcusync.expedited kernel parameter. This > > makes it easier to use rcusync.expedited functionality in cases where > > specifying kernel boot parameters should be avoided. > > > > Reported-by: John Stultz <[email protected]> > > Signed-off-by: Paul E. McKenney <[email protected]> > > Tested-by: John Stultz <[email protected]> > > Acked-by: John Stultz <[email protected]> > > Cc: <[email protected]> # 4.4.x- > > I think it probably makes sense to make this the default on !RT at > least with a separate patch w/o stable cc'd. While most use cases > will be fine with the latency on write path, it also means that the > reader side is blocked for the duration which can hurt. rwsem implies > a lot more readers and thus more read lock operations than writes. > It's weird to trade off higher latency for lower cpu usage when it > would also slow down all readers.
NAK, no expedited muck by default. There's more than just RT that doesn't like IPI sprays.
