linux-kernel - Re: [External] Re: [PATCH v2] mm: add new syscall pidfd_set

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Date:   Tue, 22 Nov 2022 16:33:09 +0800
From:   Zhongkun He <hezhongkun.hzk@...edance.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, corbet@....net,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [External] Re: [PATCH v2] mm: add new syscall
 pidfd_set_mempolicy().

Hi Michal, thanks for your replay and suggestions.

> 
> Yes the memory consumption is going to increase but the question is
> whether this is something that is a real problem. Is it really common to
> have many vmas with a dedicated policy?

Yes, it does not a realy problem.

> 
> What I am arguing here is that there are essentially 2 ways forward.
> Either we continue to build up on top of the existing and arguably very
> fragile code and make it even more subtle or follow a general pattern of
> a proper reference counting (with usual tricks to reduce cache line
> bouncing and similar issues). I do not really see why memory policies
> should be any different and require very special treatment.
> 

I got it. It is rather subtle and easy to get wrong if we push forward
with the existing way and it is a good opportunity to get from the
existing subtle model. I will try that on next version.

__
Best Regards,
Zhongkun