On Fri, Dec 19, 2008 at 07:52:42AM +0100, Nick Piggin wrote: > On Thu, Dec 18, 2008 at 10:34:52PM -0800, Dave Hansen wrote: > > Yes, I think it can tolerate it. There's a lot of work to do, and we > > already have to go touch all the other per-cpu objects. There also > > tends to be writeout when this happens, so I don't think a few seconds, > > even, will be noticed. > > That would be good. After the first patch, mnt_want_write still shows up > on profiles and almost oall the hits come right after the msync from > the smp_mb there. > > It would be really nice to use RCU here. I think it might allow us to > eliminate the memory barriers. Actually we might be able to use a seqcounter to eliminate the most expensive (smp_mb()) barrier. But that's more code and adds a couple of smp_rmb()s which would be slower on some architectures.... Not to mention more code and branches. But I'll investigate that option if RCU is ruled out. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
