Andrew Morton wrote: >Nick Piggin wrote: > >>Hi, >> >>The two namesys patches help kbuild quite a lot here. >>http://www.kerneltrap.org/~npiggin/vm/1/ >> >>The patches can be found at >>http://thebsh.namesys.com/snapshots/LATEST/extra/ >> > >I played with these back in July. Had a few stability problems then but >yes, they did speed up some workloads a lot. > > > >>I don't have much to comment on the patches. They do include >>some cleanup stuff which should be broken out. >> > >Yup. See below - it's six months old though. > > >>I don't really understand the dont-rotate-active-list patch: >>I don't see why we're losing LRU information because the pages >>that go to the head of the active list get their referenced >>bits cleared. >> > >Yes, I do think that the "LRU" is a bit of a misnomer - it's very >approximate and only really suits simple workloads. I suspect that once >things get hot and heavy the "lru" is only four-deep: >unreferenced/inactive, referenced/inactive, unreferenced/active and >referenced/active. > Yep that was my thinking. > >Can you test the patches separately, see what bits are actually helping? > OK, I'll see how the second chance one alone does. By the way, what do you think of this? Did I miss something non obvious? Seems to make little difference on the benchmarks. Without the patch, the active list would generally be attacked more aggressively.