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SubjectRe: [PATCH 1/1] mm/page_alloc: add scheduling point to free_unref_page_list
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On 3/3/22 00:34, Andrew Morton wrote:
> On Tue, 1 Mar 2022 20:38:25 -0500 wangjianxing <wangjianxing@loongson.cn> wrote:
>
>> free a large list of pages maybe cause rcu_sched starved on
>> non-preemptible kernels
>>
>> rcu: rcu_sched kthread starved for 5359 jiffies! g454793 f0x0
>> RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=19
>> [...]
>> Call Trace:
>> free_unref_page_list+0x19c/0x270
>> release_pages+0x3cc/0x498
>> tlb_flush_mmu_free+0x44/0x70
>> zap_pte_range+0x450/0x738
>> unmap_page_range+0x108/0x240
>> unmap_vmas+0x74/0xf0
>> unmap_region+0xb0/0x120
>> do_munmap+0x264/0x438
>> vm_munmap+0x58/0xa0
>> sys_munmap+0x10/0x20
>> syscall_common+0x24/0x38
>
> Thanks.
>
> How did this large list of pages come about?

Looks like it came from TLB batching. But I got lost in the maze of it
trying to figure out how large the batch can grow.

> Will people be seeing this message in upstream kernels, or is it
> specific to some caller code which you have added?
>
> Please always include details such as this so that others can determine
> whether the fix should be backported into -stable kernels.
>
>

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