Thanks Suren for looping in On Fri, Aug 23, 2024 at 4:39 PM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote: > > On Wed, Aug 21, 2024 at 2:47 PM Barry Song <21cnbao@xxxxxxxxx> wrote: > > > > On Wed, Aug 21, 2024 at 8:46 PM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > > > On Fri 16-08-24 07:48:01, gaoxu wrote: > > > > Replace lruvec_add_folio with lruvec_add_folio_tail in the lru_lazyfree_fn: > > > > 1. The lazy-free folio is added to the LRU_INACTIVE_FILE list. If it's > > > > moved to the LRU tail, it allows for faster release lazy-free folio and > > > > reduces the impact on file refault. > > > > > > This has been discussed when MADV_FREE was introduced. The question was > > > whether this memory has a lower priority than other inactive memory that > > > has been marked that way longer ago. Also consider several MADV_FREE > > > users should they be LIFO from the reclaim POV? Thinking from the user's perspective, it seems to me that FIFO within MADV_FREE'ed pages makes more sense. As a user I expect the longer a MADV_FREE'ed page hasn't been touched, the chances are higher that it may not be around anymore. > > > > The priority of this memory compared to other inactive memory that has been > > marked for a longer time likely depends on the user's expectations - How soon > > do users expect MADV_FREE to be reclaimed compared with old file folios. > > > > art guys moved to MADV_FREE from MADV_DONTNEED without any > > useful performance data and reason in the changelog: > > https://android-review.googlesource.com/c/platform/art/+/2633132 > > > > Since art is the Android Java heap, it can be quite large. This increases the > > likelihood of packing the file LRU and reduces the chances of reclaiming > > anonymous memory, which could result in more file re-faults while helping > > anonymous folio persist longer in memory. Individual heaps of android apps are not big, and even in there we don't call MADV_FREE on the entire heap. > > > > I am really curious why art guys have moved to MADV_FREE if we have > > an approach to reach them. Honestly, it makes little sense as a user that calling MADV_FREE on an anonymous mapping will impact file LRU. That was never the intention with our ART change.
