Messages in this thread | | | Date | Fri, 15 Apr 2022 10:23:18 +0800 | Subject | Re: [PATCH v10 06/14] mm: multi-gen LRU: minimal implementation | From | Chen Wandun <> |
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在 2022/4/15 4:53, Yu Zhao 写道: > On Thu, Apr 14, 2022 at 07:47:54PM +0800, Chen Wandun wrote: >> On 2022/4/7 11:15, Yu Zhao wrote: >>> +static void inc_min_seq(struct lruvec *lruvec) >>> +{ >>> + int type; >>> + struct lru_gen_struct *lrugen = &lruvec->lrugen; >>> + >>> + VM_BUG_ON(!seq_is_valid(lruvec)); >>> + >>> + for (type = 0; type < ANON_AND_FILE; type++) { >>> + if (get_nr_gens(lruvec, type) != MAX_NR_GENS) >>> + continue; >> I'm confused about relation between aging and LRU list operation. >> >> In function inc_max_seq, both min_seq and max_seq will increase, >> the lrugen->lists[] indexed by lru_gen_from_seq(max_seq + 1) may >> be non-empty? > Yes. > >> for example, >> before inc_max_seq: >> min_seq == 0, lrugen->lists[0][type][zone] >> max_seq ==3, lrugen->lists[3][type][zone] >> >> after inc_max_seq: >> min_seq ==1, lrugen->lists[1][type][zone] >> max_seq ==4, lrugen->lists[0][type][zone] >> >> If lrugen->lists[0][type][zone] is not empty before inc_max_seq and it is >> the most inactive list,however lurgen->lists[0][type][zone] will become >> the most active list after inc_max_seq. > Correct. > >> So, in this place, >> >> if (get_nr_gens(lruvec, type) != MAX_NR_GENS) >> continue; >> >> should change to >> >> if (get_nr_gens(lruvec, type) == MAX_NR_GENS) >> continue; > No, because max/min_seq will overlap if we do so. > > lrugen->lists[max_seq+1] can only be non-empty for anon LRU, for a > couple of reasons: > 1. We can't swap at all. > 2. Swapping is constrained, e.g., swapfile is full. > > Both cases are similar to a producer (the aging) overrunning a > consumer (the eviction). We used to handle them, but I simplified the > code because I don't feel they are worth handling [1].
Can lrugen->lists[max_seq+1] also be non-empty for file LRU? such as in dont reclaim mapped file page case(isolation will fail).
If so, after aging, eviction will reclaim memory start from lrugen->lists[min_seq+1], but some oldest file page still remain in lrugen->lists[max_seq+1].
sort_folio can help to put misplaced pages to the right LRU list, but in this case, it does't help, because sort_folio only sort lrugen->lists[min_seq+1].
Thanks Wandun > > [1] https://lore.kernel.org/r/CAOUHufbDfwgm8PgCGkhCjbhMbm=fekfjgRR56NL-j+5iUGfVuw@mail.gmail.com/ > .
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