On Wed, 2009-03-18 at 18:03 -0700, David Miller wrote: > From: Gregory Haskins <ghaskins@xxxxxxxxxx> > Date: Wed, 18 Mar 2009 17:54:04 -0400 > > > Note that -rt doesnt typically context-switch under contention anymore > > since we introduced adaptive-locks. Also note that the contention > > against the lock is still contention, regardless of whether you have -rt > > or not. Its just that the slow-path to handle the contended case for > > -rt is more expensive than mainline. However, once you have the > > contention as stated, you have already lost. > > First, contention is not implicitly a bad thing. > Its a bad thing when it does not scale. > Second, if the -rt kernel is doing adaptive spinning I see no > reason why that adaptive spinning is not kicking in here to > make this problem just go away. > If only the first of N contending threads gets to spin, 2..N would context-switch. > This lock is held for mere cycles, just to unlink an SKB from > the networking qdisc, and then it is immediately released. For very short hold times, and heavy contention, as well as for scalability, the solution may lie in tunable spinner-count and adaptive spinner time-out. Sven > -- > To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
