Re: [PATCH RFC 0/3] optimize kswapd when it does reclaim for hugepage

[hejianet <hejianet@gmail.com>]

Hi Michal
Thanks for the comments, I will resend the patch as per your
comment after my 2 weeks vacation.

B.R.
Jia

On 25/01/2017 12:46 AM, Michal Hocko wrote:
> On Tue 24-01-17 15:49:01, Jia He wrote:
>> If there is a server with uneven numa memory layout:
>> available: 7 nodes (0-6)
>> node 0 cpus: 0 1 2 3 4 5 6 7
>> node 0 size: 6603 MB
>> node 0 free: 91 MB
>> node 1 cpus:
>> node 1 size: 12527 MB
>> node 1 free: 157 MB
>> node 2 cpus:
>> node 2 size: 15087 MB
>> node 2 free: 189 MB
>> node 3 cpus:
>> node 3 size: 16111 MB
>> node 3 free: 205 MB
>> node 4 cpus: 8 9 10 11 12 13 14 15
>> node 4 size: 24815 MB
>> node 4 free: 310 MB
>> node 5 cpus:
>> node 5 size: 4095 MB
>> node 5 free: 61 MB
>> node 6 cpus:
>> node 6 size: 22750 MB
>> node 6 free: 283 MB
>> node distances:
>> node   0   1   2   3   4   5   6
>>   0:  10  20  40  40  40  40  40
>>   1:  20  10  40  40  40  40  40
>>   2:  40  40  10  20  40  40  40
>>   3:  40  40  20  10  40  40  40
>>   4:  40  40  40  40  10  20  40
>>   5:  40  40  40  40  20  10  40
>>   6:  40  40  40  40  40  40  10
>>
>> In this case node 5 has less memory and we will alloc the hugepages
>> from these nodes one by one after we trigger
>> echo 4000 > /proc/sys/vm/nr_hugepages
>>
>> Then the kswapd5 will take 100% cpu for a long time. This is a livelock
>> issue in kswapd. This patch set fixes it.
>
> It would be really helpful to describe what is the issue and whether it
> is specific to the configuration above. Also a highlevel overview of the
> fix and why it is the right approach would be appreciated.
>
>> The 3rd patch improves the kswapd's bad performance significantly.
>
> Numbers?
>
>> Jia He (3):
>>   mm/hugetlb: split alloc_fresh_huge_page_node into fast and slow path
>>   mm, vmscan: limit kswapd loop if no progress is made
>>   mm, vmscan: correct prepare_kswapd_sleep return value
>>
>>  mm/hugetlb.c |  9 +++++++++
>>  mm/vmscan.c  | 28 ++++++++++++++++++++++++----
>>  2 files changed, 33 insertions(+), 4 deletions(-)
>>
>> --
>> 2.5.5
>>
>

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