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Date:   Thu, 13 Oct 2022 20:50:48 +0800
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Subject: Re: [External] Re: [RFC] mm: add new syscall pidfd_set_mempolicy()
To:     Michal Hocko <mhocko@suse.com>
Cc:     corbet@lwn.net, akpm@linux-foundation.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
        linux-doc@vger.kernel.org, wuyun.abel@bytedance.com
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From:   Zhongkun He <hezhongkun.hzk@bytedance.com>
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>> Hi Michal
>>
>> Could we try to change the MPOL_F_SHARED flag to MPOL_F_STATIC to
>> mark static mempolicy which cannot be freed, and mpol_needs_cond_ref
>> can use MPOL_F_STATIC to avoid freeing  the static mempolicy.
> 
> Wouldn't it make more sense to get rid of a different treatment and
> treat all memory policies the same way?

I found a case, not sure if it makes sense. If there is no policy
in task->mempolicy, the use of atomic_{inc,dec} can be skiped
according  to MPOL_F_STATIC. Atomic_{inc,dec} in hot path may reduces 
performance.

Thanks.