On Thu, Nov 16, 2017 at 02:07:46PM +0100, Michal Hocko wrote: > On Thu 16-11-17 21:48:05, Byungchul Park wrote: > > On 11/16/2017 9:02 PM, Michal Hocko wrote: > > > for each struct page. So you are doubling the size. Who is going to > > > enable this config option? You are moving this to page_ext in a later > > > patch which is a good step but it doesn't go far enough because this > > > still consumes those resources. Is there any problem to make this > > > kernel command line controllable? Something we do for page_owner for > > > example? > > > > Sure. I will add it. > > > > > Also it would be really great if you could give us some measures about > > > the runtime overhead. I do not expect it to be very large but this is > > > > The major overhead would come from the amount of additional memory > > consumption for 'lockdep_map's. > > yes > > > Do you want me to measure the overhead by the additional memory > > consumption? > > > > Or do you expect another overhead? > > I would be also interested how much impact this has on performance. I do > not expect it would be too large but having some numbers for cache cold > parallel kbuild or other heavy page lock workloads. Hello Michal, I measured 'cache cold parallel kbuild' on my qemu machine. The result varies much so I cannot confirm, but I think there's no meaningful difference between before and after applying crossrelease to page locks. Actually, I expect little overhead in lock_page() and unlock_page() even after applying crossreleas to page locks, but only expect a bit overhead by additional memory consumption for 'lockdep_map's per page. I run the following instructions within "QEMU x86_64 4GB memory 4 cpus": make clean echo 3 > drop_caches time make -j4 The results are: # w/o page lock tracking At the 1st try, real 5m28.105s user 17m52.716s sys 3m8.871s At the 2nd try, real 5m27.023s user 17m50.134s sys 3m9.289s At the 3rd try, real 5m22.837s user 17m34.514s sys 3m8.097s # w/ page lock tracking At the 1st try, real 5m18.158s user 17m18.200s sys 3m8.639s At the 2nd try, real 5m19.329s user 17m19.982s sys 3m8.345s At the 3rd try, real 5m19.626s user 17m21.363s sys 3m9.869s I think thers's no meaningful difference on my small machine. -- Thanks, Byungchul
