* Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > On Tue, 23 Mar 2010, Ingo Molnar wrote: > > > > It shows a very brutal amount of page fault invoked mmap_sem spinning > > overhead. > > Isn't this already fixed? It's the same old "x86-64 rwsemaphores are using > the shit-for-brains generic version" thing, and it's fixed by > > 1838ef1 x86-64, rwsem: 64-bit xadd rwsem implementation > 5d0b723 x86: clean up rwsem type system > 59c33fa x86-32: clean up rwsem inline asm statements Ah, indeed! > NOTE! None of those are in 2.6.33 - they were merged afterwards. But they > are in 2.6.34-rc1 (and obviously current -git). So Anton would have to > compile his own kernel to test his load. another option is to run the rawhide kernel via something like: yum update --enablerepo=development kernel this will give kernel-2.6.34-0.13.rc1.git1.fc14.x86_64, which has those changes included. OTOH that kernel has debugging [lockdep] enabled so it might not be comparable. > We could mark them as stable material if the load in question is a real load > rather than just a test-case. On one of the random page-fault benchmarks the > rwsem fix was something like a 400% performance improvement, and it was > apparently visible in real life on some crazy SGI "initialize huge heap > concurrently on lots of threads" load. > > Side note: the reason the spinlock sucks is because of the fair ticket > locks, it really does all the wrong things for the rwsem code. That's why > old kernels don't show it - the old unfair locks didn't show the same kind > of behavior. Yeah. Ingo -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>