On Wed, 29 Aug 2018 16:15:37 -0700 Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > On Wed, Aug 29, 2018 at 4:12 PM Nicholas Piggin <npiggin@xxxxxxxxx> wrote: > > > > Dirty micro fault seems to be the big one for my Skylake, takes 300 > > nanoseconds per access. Accessed takes about 100. (I think, have to > > go over my benchmark a bit more carefully and re-test). > > Yeah, but they only happen for shared areas after fork, which sounds > like it shouldn't be a big deal in most cases. You might be right there. > > And I'm not entirely objecting to your patch per se, I just would want > to keep the accessed bit changes separate from the dirty bit ones. > > *If* somebody has bisectable issues with it (performance or not), it > will then be clearer what the exact issue is. Yeah that makes a lot of sense. I'll do a bit more testing and send Andrew a respin at least with those split (and a good comment for the dirty bit vs unmap handling that you pointed out). Thanks, Nick
