Re: [PATCH v2] mm/hugetlb: defer free_huge_page() to a workqueue

[Waiman Long]

On 12/16/19 10:38 AM, Waiman Long wrote:
> On 12/16/19 8:26 AM, Michal Hocko wrote:
>> On Thu 12-12-19 15:52:20, Waiman Long wrote:
>>> On 12/12/19 2:22 PM, Mike Kravetz wrote:
>>>> On 12/12/19 11:04 AM, Davidlohr Bueso wrote:
>>>>> There have been deadlock reports[1, 2] where put_page is called
>>>>> from softirq context and this causes trouble with the hugetlb_lock,
>>>>> as well as potentially the subpool lock.
>>>>>
>>>>> For such an unlikely scenario, lets not add irq dancing overhead
>>>>> to the lock+unlock operations, which could incur in expensive
>>>>> instruction dependencies, particularly when considering hard-irq
>>>>> safety. For example PUSHF+POPF on x86.
>>>>>
>>>>> Instead, just use a workqueue and do the free_huge_page() in regular
>>>>> task context.
>>>>>
>>>>> [1] https://lore.kernel.org/lkml/20191211194615.18502-1-longman@xxxxxxxxxx/
>>>>> [2] https://lore.kernel.org/lkml/20180905112341.21355-1-aneesh.kumar@xxxxxxxxxxxxx/
>>>>>
>>>>> Reported-by: Waiman Long <longman@xxxxxxxxxx>
>>>>> Reported-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
>>>>> Signed-off-by: Davidlohr Bueso <dbueso@xxxxxxx>
>>>> Thank you Davidlohr.
>>>>
>>>> The patch does seem fairly simple and straight forward.  I need to brush up
>>>> on my workqueue knowledge to provide a full review.
>>>>
>>>> Longman,
>>>> Do you have a test to reproduce the issue?  If so, can you try running with
>>>> this patch.
>>> Yes, I do have a test that can reproduce the issue. I will run it with
>>> the patch and report the status tomorrow.
>> Can you extract guts of the testcase and integrate them into hugetlb
>> test suite?

BTW, what hugetlb test suite are you talking about?

Cheers,
Longman