On Wednesday 12 December 2007 16:11, Dave Kleikamp wrote: > On Wed, 2007-12-12 at 15:57 +1100, Nick Piggin wrote: > > On Tuesday 11 December 2007 08:30, Dave Kleikamp wrote: > > > Nick, > > > I've played with the fast_gup patch a bit. I was able to find a > > > problem in follow_hugetlb_page() that Adam Litke fixed. I'm haven't > > > been brave enough to implement it on any other architectures, but I did > > > add a default that takes mmap_sem and calls the normal > > > get_user_pages() if the architecture doesn't define fast_gup(). I put > > > it in linux/mm.h, for lack of a better place, but it's a little kludgy > > > since I didn't want mm.h to have to include sched.h. This patch is > > > against 2.6.24-rc4. It's not ready for inclusion yet, of course. > > > > Hi Dave, > > > > Thanks so much. This makes it much more a complete patch (although > > still missing the "normal page" detection). > > > > I think I missed -- or forgot -- what was the follow_hugetlb_page > > problem? > > Badari found a problem running some tests and handed it off to me to > look at. I didn't share it publicly. Anyway, we were finding that > fastgup was taking the slow path almost all the time with huge pages. > The problem was that follow_hugetlb_page was failing to fault on a > non-writable page when it needed a writable one. So we'd keep seeing a > non-writable page over and over. This is fixed in 2.6.24-rc5.
Ah yes, I just saw that fix in the changelog. So not a problem with my patch as such, but good to get that fixed. > > Anyway, I am hoping that someone will one day and test if this and > > find it helps their workload, but on the other hand, if it doesn't > > help anyone then we don't have to worry about adding it to the > > kernel ;) I don't have any real setups that hammers DIO with threads. > > I'm guessing DB2 and/or Oracle does? > > I'll try to get someone to run a DB2 benchmark and see what it looks > like. That would be great if you could. Thanks, Nick -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
