On Wed, Nov 13, 2024 at 7:02 AM Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx> wrote: > > On Wed, Nov 13, 2024 at 02:28:16PM +0000, Lorenzo Stoakes wrote: > > On Tue, Nov 12, 2024 at 11:46:32AM -0800, Suren Baghdasaryan wrote: > > > Back when per-vma locks were introduces, vm_lock was moved out of > > > vm_area_struct in [1] because of the performance regression caused by > > > false cacheline sharing. Recent investigation [2] revealed that the > > > regressions is limited to a rather old Broadwell microarchitecture and > > > even there it can be mitigated by disabling adjacent cacheline > > > prefetching, see [3]. > > > > I don't see a motivating reason as to why we want to do this? We increase > > memory usage here which is not good, but later lock optimisation mitigates > > it, but why wouldn't we just do the lock optimisations and use less memory > > overall? > > I worded this badly. To clarify: > > I don't see a motivating reason _in the commit message_ as to why we want > to do this. > > I am certain there are, in fact Mateusz and Vlastimil have provided them. > > So my review is - let's just put these there :) Yeah, I had trouble wording all the reasons because in my head it was simply "the right thing to do". Now with all your input my job has become much easier :) Thanks folks!
