Re: [PATCH v2 RESEND 2/2] mm: ignore memory.min of abandoned memory cgroups

From: kbuild test robot
Date: Wed May 02 2018 - 21:09:18 EST

Hi Roman,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on mmotm/master]
[also build test ERROR on next-20180502]
[cannot apply to v4.17-rc3]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url: https://github.com/0day-ci/linux/commits/Roman-Gushchin/mm-introduce-memory-min/20180503-064145
base: git://git.cmpxchg.org/linux-mmotm.git master
config: i386-tinyconfig (attached as .config)
compiler: gcc-7 (Debian 7.3.0-16) 7.3.0
reproduce:
# save the attached .config to linux build tree
make ARCH=i386

All errors (new ones prefixed by >>):

mm/vmscan.c: In function 'shrink_node':
>> mm/vmscan.c:2555:9: error: implicit declaration of function 'cgroup_is_populated'; did you mean 'cgroup_bpf_put'? [-Werror=implicit-function-declaration]
if (cgroup_is_populated(memcg->css.cgroup))
^~~~~~~~~~~~~~~~~~~
cgroup_bpf_put
mm/vmscan.c:2555:34: error: dereferencing pointer to incomplete type 'struct mem_cgroup'
if (cgroup_is_populated(memcg->css.cgroup))
^~
cc1: some warnings being treated as errors

vim +2555 mm/vmscan.c

2520
2521 static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
2522 {
2523 struct reclaim_state *reclaim_state = current->reclaim_state;
2524 unsigned long nr_reclaimed, nr_scanned;
2525 bool reclaimable = false;
2526
2527 do {
2528 struct mem_cgroup *root = sc->target_mem_cgroup;
2529 struct mem_cgroup_reclaim_cookie reclaim = {
2530 .pgdat = pgdat,
2531 .priority = sc->priority,
2532 };
2533 unsigned long node_lru_pages = 0;
2534 struct mem_cgroup *memcg;
2535
2536 memset(&sc->nr, 0, sizeof(sc->nr));
2537
2538 nr_reclaimed = sc->nr_reclaimed;
2539 nr_scanned = sc->nr_scanned;
2540
2541 memcg = mem_cgroup_iter(root, NULL, &reclaim);
2542 do {
2543 unsigned long lru_pages;
2544 unsigned long reclaimed;
2545 unsigned long scanned;
2546
2547 switch (mem_cgroup_protected(root, memcg)) {
2548 case MEMCG_PROT_MIN:
2549 /*
2550 * Hard protection.
2551 * If there is no reclaimable memory, OOM.
2552 * Abandoned cgroups are loosing protection,
2553 * because OOM killer won't release any memory.
2554 */
> 2555 if (cgroup_is_populated(memcg->css.cgroup))
2556 continue;
2557 case MEMCG_PROT_LOW:
2558 /*
2559 * Soft protection.
2560 * Respect the protection only as long as
2561 * there is an unprotected supply
2562 * of reclaimable memory from other cgroups.
2563 */
2564 if (!sc->memcg_low_reclaim) {
2565 sc->memcg_low_skipped = 1;
2566 continue;
2567 }
2568 memcg_memory_event(memcg, MEMCG_LOW);
2569 break;
2570 case MEMCG_PROT_NONE:
2571 break;
2572 }
2573
2574 reclaimed = sc->nr_reclaimed;
2575 scanned = sc->nr_scanned;
2576 shrink_node_memcg(pgdat, memcg, sc, &lru_pages);
2577 node_lru_pages += lru_pages;
2578
2579 if (memcg)
2580 shrink_slab(sc->gfp_mask, pgdat->node_id,
2581 memcg, sc->priority);
2582
2583 /* Record the group's reclaim efficiency */
2584 vmpressure(sc->gfp_mask, memcg, false,
2585 sc->nr_scanned - scanned,
2586 sc->nr_reclaimed - reclaimed);
2587
2588 /*
2589 * Direct reclaim and kswapd have to scan all memory
2590 * cgroups to fulfill the overall scan target for the
2591 * node.
2592 *
2593 * Limit reclaim, on the other hand, only cares about
2594 * nr_to_reclaim pages to be reclaimed and it will
2595 * retry with decreasing priority if one round over the
2596 * whole hierarchy is not sufficient.
2597 */
2598 if (!global_reclaim(sc) &&
2599 sc->nr_reclaimed >= sc->nr_to_reclaim) {
2600 mem_cgroup_iter_break(root, memcg);
2601 break;
2602 }
2603 } while ((memcg = mem_cgroup_iter(root, memcg, &reclaim)));
2604
2605 if (global_reclaim(sc))
2606 shrink_slab(sc->gfp_mask, pgdat->node_id, NULL,
2607 sc->priority);
2608
2609 if (reclaim_state) {
2610 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2611 reclaim_state->reclaimed_slab = 0;
2612 }
2613
2614 /* Record the subtree's reclaim efficiency */
2615 vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true,
2616 sc->nr_scanned - nr_scanned,
2617 sc->nr_reclaimed - nr_reclaimed);
2618
2619 if (sc->nr_reclaimed - nr_reclaimed)
2620 reclaimable = true;
2621
2622 if (current_is_kswapd()) {
2623 /*
2624 * If reclaim is isolating dirty pages under writeback,
2625 * it implies that the long-lived page allocation rate
2626 * is exceeding the page laundering rate. Either the
2627 * global limits are not being effective at throttling
2628 * processes due to the page distribution throughout
2629 * zones or there is heavy usage of a slow backing
2630 * device. The only option is to throttle from reclaim
2631 * context which is not ideal as there is no guarantee
2632 * the dirtying process is throttled in the same way
2633 * balance_dirty_pages() manages.
2634 *
2635 * Once a node is flagged PGDAT_WRITEBACK, kswapd will
2636 * count the number of pages under pages flagged for
2637 * immediate reclaim and stall if any are encountered
2638 * in the nr_immediate check below.
2639 */
2640 if (sc->nr.writeback && sc->nr.writeback == sc->nr.taken)
2641 set_bit(PGDAT_WRITEBACK, &pgdat->flags);
2642
2643 /*
2644 * Tag a node as congested if all the dirty pages
2645 * scanned were backed by a congested BDI and
2646 * wait_iff_congested will stall.
2647 */
2648 if (sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
2649 set_bit(PGDAT_CONGESTED, &pgdat->flags);
2650
2651 /* Allow kswapd to start writing pages during reclaim.*/
2652 if (sc->nr.unqueued_dirty == sc->nr.file_taken)
2653 set_bit(PGDAT_DIRTY, &pgdat->flags);
2654
2655 /*
2656 * If kswapd scans pages marked marked for immediate
2657 * reclaim and under writeback (nr_immediate), it
2658 * implies that pages are cycling through the LRU
2659 * faster than they are written so also forcibly stall.
2660 */
2661 if (sc->nr.immediate)
2662 congestion_wait(BLK_RW_ASYNC, HZ/10);
2663 }
2664
2665 /*
2666 * Legacy memcg will stall in page writeback so avoid forcibly
2667 * stalling in wait_iff_congested().
2668 */
2669 if (!global_reclaim(sc) && sane_reclaim(sc) &&
2670 sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
2671 set_memcg_congestion(pgdat, root, true);
2672
2673 /*
2674 * Stall direct reclaim for IO completions if underlying BDIs
2675 * and node is congested. Allow kswapd to continue until it
2676 * starts encountering unqueued dirty pages or cycling through
2677 * the LRU too quickly.
2678 */
2679 if (!sc->hibernation_mode && !current_is_kswapd() &&
2680 current_may_throttle() && pgdat_memcg_congested(pgdat, root))
2681 wait_iff_congested(BLK_RW_ASYNC, HZ/10);
2682
2683 } while (should_continue_reclaim(pgdat, sc->nr_reclaimed - nr_reclaimed,
2684 sc->nr_scanned - nr_scanned, sc));
2685
2686 /*
2687 * Kswapd gives up on balancing particular nodes after too
2688 * many failures to reclaim anything from them and goes to
2689 * sleep. On reclaim progress, reset the failure counter. A
2690 * successful direct reclaim run will revive a dormant kswapd.
2691 */
2692 if (reclaimable)
2693 pgdat->kswapd_failures = 0;
2694
2695 return reclaimable;
2696 }
2697

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