On 1/11/24 1:54 PM, Andrew Morton wrote: > On Thu, 11 Jan 2024 10:54:45 -0800 Jianfeng Wang <jianfeng.w.wang@xxxxxxxxxx> wrote: > >> >>> Unless you can show any actual runtime effect of this patch then I think >>> it shouldn't be merged. >>> >> >> Thanks for raising your concern. >> I'd call it a trade-off rather than "not really correct". Look at >> unmap_region() / free_pages_and_swap_cache() written by Linus. These are in >> favor of this pattern, which indicates that the trade-off (i.e. draining >> local CPU or draining all CPUs or no draining at all) had been made in the >> same way in the past. I don't have a specific runtime effect to provide, >> except that it will free 10s kB pages immediately during OOM. > > I don't think it's necessary to run lru_add_drain() for each vma. Once > we've done it it once, it can be skipped for additional vmas. > Agreed. > That's pretty minor because the second and successive calls will be > cheap. But it becomes much more significant if we switch to > lru_add_drain_all(), which sounds like what we should be doing here. > Is it possible? > What do you both think of adding lru_add_drain_all() prior to the for loop?
