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authorChen Wandun <chenwandun@huawei.com>2022-11-18 21:38:50 +0800
committerAndrew Morton <akpm@linux-foundation.org>2022-11-22 18:50:44 -0800
commitde1ccfb648243a031cfbdc2d5571dfdaf5023106 (patch)
tree09decb9d6540901964f392c87810819dd72e07d7 /mm
parent7fb0728a9b005b8fc55e835529047cca15191031 (diff)
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swapfile: fix soft lockup in scan_swap_map_slots
A softlockup occurs in scan free swap slot under huge memory pressure. The test scenario is: 64 CPU cores, 64GB memory, and 28 zram devices, the disksize of each zram device is 50MB. LATENCY_LIMIT is used to prevent softlockups in scan_swap_map_slots(), but the real loop number would more than LATENCY_LIMIT because of "goto checks and goto scan" repeatly without decreasing latency limit. In order to fix it, decrease latency_ration in advance. There is also a suspicious place that will cause softlockups in get_swap_pages(). In this function, the "goto start_over" may result in continuous scanning of the swap partition. If there is no cond_sched in scan_swap_map_slots(), it would cause a softlockup (I am not sure about this). WARN: soft lockup - CPU#11 stuck for 11s! [kswapd0:466] CPU: 11 PID: 466 Comm: kswapd@ Kdump: loaded Tainted: G dump backtrace+0x0/0x1le4 show stack+0x20/@x2c dump_stack+0xd8/0x140 watchdog print_info+0x48/0x54 watchdog_process_before_softlockup+0x98/0xa0 watchdog_timer_fn+0xlac/0x2d0 hrtimer_rum_queues+0xb0/0x130 hrtimer_interrupt+0x13c/0x3c0 arch_timer_handler_virt+0x3c/0x50 handLe_percpu_devid_irq+0x90/0x1f4 handle domain irq+0x84/0x100 gic_handle_irq+0x88/0x2b0 e11 ira+0xhB/Bx140 scan_swap_map_slots+0x678/0x890 get_swap_pages+0x29c/0x440 get_swap_page+0x120/0x2e0 add_to_swap+UX2U/0XyC shrink_page_list+0x5d0/0x152c shrink_inactive_list+0xl6c/Bx500 shrink_lruvec+0x270/0x304 WARN: soft lockup - CPU#32 stuck for 11s! [stress-ng:309915] watchdog_timer_fn+0x1ac/0x2d0 __run_hrtimer+0x98/0x2a0 __hrtimer_run_queues+0xb0/0x130 hrtimer_interrupt+0x13c/0x3c0 arch_timer_handler_virt+0x3c/0x50 handle_percpu_devid_irq+0x90/0x1f4 __handle_domain_irq+0x84/0x100 gic_handle_irq+0x88/0x2b0 el1_irq+0xb8/0x140 get_swap_pages+0x1e8/0x440 get_swap_page+0x1c8/0x2e0 add_to_swap+0x20/0x9c shrink_page_list+0x5d0/0x152c reclaim_pages+0x160/0x310 madvise_cold_or_pageout_pte_range+0x7bc/0xe3c walk_pmd_range.isra.0+0xac/0x22c walk_pud_range+0xfc/0x1c0 walk_pgd_range+0x158/0x1b0 __walk_page_range+0x64/0x100 walk_page_range+0x104/0x150 Link: https://lkml.kernel.org/r/20221118133850.3360369-1-chenwandun@huawei.com Fixes: 048c27fd7281 ("[PATCH] swap: scan_swap_map latency breaks") Signed-off-by: Chen Wandun <chenwandun@huawei.com> Reviewed-by: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hugh@veritas.com> Cc: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: Nanyong Sun <sunnanyong@huawei.com> Cc: <xialonglong1@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/swapfile.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 5fc1237a9f21..72e481aacd5d 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -973,23 +973,23 @@ done:
scan:
spin_unlock(&si->lock);
while (++offset <= READ_ONCE(si->highest_bit)) {
- if (swap_offset_available_and_locked(si, offset))
- goto checks;
if (unlikely(--latency_ration < 0)) {
cond_resched();
latency_ration = LATENCY_LIMIT;
scanned_many = true;
}
+ if (swap_offset_available_and_locked(si, offset))
+ goto checks;
}
offset = si->lowest_bit;
while (offset < scan_base) {
- if (swap_offset_available_and_locked(si, offset))
- goto checks;
if (unlikely(--latency_ration < 0)) {
cond_resched();
latency_ration = LATENCY_LIMIT;
scanned_many = true;
}
+ if (swap_offset_available_and_locked(si, offset))
+ goto checks;
offset++;
}
spin_lock(&si->lock);