On Wed, 2013-08-07 at 11:03 +1000, David Gibson wrote: > On Tue, Aug 06, 2013 at 05:18:44PM -0700, Davidlohr Bueso wrote: > > On Mon, 2013-08-05 at 16:36 +0900, Joonsoo Kim wrote: > > > > Any mapping that doesn't use the reserved pool, not just > > > > MAP_NORESERVE. For example, if a process makes a MAP_PRIVATE mapping, > > > > then fork()s then the mapping is instantiated in the child, that will > > > > not draw from the reserved pool. > > > > > > > > > Should we ensure them to allocate the last hugepage? > > > > > They map a region with MAP_NORESERVE, so don't assume that their > > > > > requests > > > > > always succeed. > > > > > > > > If the pages are available, people get cranky if it fails for no > > > > apparent reason, MAP_NORESERVE or not. They get especially cranky if > > > > it sometimes fails and sometimes doesn't due to a race condition. > > > > > > Hello, > > > > > > Hmm... Okay. I will try to implement another way to protect race > > > condition. > > > Maybe it is the best to use a table mutex :) > > > Anyway, please give me a time, guys. > > > > So another option is to take the mutex table patchset for now as it > > *does* improve things a great deal, then, when ready, get rid of the > > instantiation lock all together. > > We still don't have a solid proposal for doing that. Joonsoo Kim's > patchset misses cases (non reserved mappings). I'm also not certain > there aren't a few edge cases which can lead to even reserved mappings > failing, and if that happens the patches will lead to livelock. >
Exactly, which is why I suggest minimizing the lock contention until we do have such a proposal. > Getting rid of the instantiation mutex is a lot harder than it appears. > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
