On 05/01/2012 06:14 PM, Peter Zijlstra wrote: > On Tue, 2012-05-01 at 15:12 +0300, Avi Kivity wrote: > > > > What's changed is not gup_fast() but the performance of munmap(), > > exit(), and exec(), no? > > If it is indeed cache related like you suggested earlier, it would be > the allocation side of things, like fork()/mmap() that suffer since > there's fewer hot pages about, but yes, anything creating/destroying > page-tables. Right. > > > What bounds the amount of memory waiting to be freed during an rcu grace > > period? > > Most RCU implementations don't have limits, so that could be quite a > lot. I think preemptible RCU has a batch limit at which point it tries > rather hard to force a grace period, but I'm not sure if even that > provides a hard limit. > > Practically though, I haven't had reports of PPC/Sparc going funny > because of this. It could be considered a DoS if a user is able to free page tables faster than rcu is able to recycle them, possibly triggering the oom killer (should that force a grace period before firing from the hip?) -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
