On Wed, Nov 24, 2021 at 1:17 PM Yang Shi <shy828301@xxxxxxxxx> wrote: > > On Wed, Nov 24, 2021 at 12:44 PM Shakeel Butt <shakeelb@xxxxxxxxxx> wrote: > > > > On Wed, Nov 24, 2021 at 12:12 PM Kirill A. Shutemov > > <kirill@xxxxxxxxxxxxx> wrote: > > > > > > On Tue, Nov 23, 2021 at 11:09:16AM -0800, Shakeel Butt wrote: > > > > The deferred THPs are split on memory pressure through shrinker > > > > callback and splitting of THP during reclaim can fail for several > > > > reasons like unable to lock the THP, under writeback or unexpected > > > > number of pins on the THP. Such pages are put back on the deferred split > > > > list for consideration later. However kernel does not update the > > > > deferred queue size on putting back the pages whose split was failed. > > > > This patch fixes that. > > > > > > Hm. No. split_huge_page_to_list() updates the queue size on split success. > > > > > > > Right. This is really convoluted. split_huge_page_to_list() is just > > assuming that if the given page is on a deferred list then it must be > > on the list returned by get_deferred_split_queue(page). The > > interaction of move_charge and deferred split seems broken. > > Because memcg code doesn't move charge for PTE mapped THP at all. See > the below comment from mem_cgroup_move_charge_pte_range(): > > "We can have a part of the split pmd here. Moving it can be done but > it would be too convoluted so simply ignore such a partial THP and > keep it in original memcg. There should be somebody mapping the head." > > BTW, did you run into any problem related to this? > No, just reading code to see if I can share code for the sync splitting of THPs.
