linux-kernel - Re: [External] Re: [PATCH] mm: hugetlb: support get/set_policy for hugetlb_vm

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Message-ID: <CABKxMyOnxiS6RsJtQEQPrnzNn-cO0Z+OGJRCUpw1M4=WANx0Dw@mail.gmail.com>
Date:   Mon, 17 Oct 2022 17:48:50 +0800
From:   黄杰 <huangjie.albert@...edance.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     songmuchun@...edance.com, Mike Kravetz <mike.kravetz@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [External] Re: [PATCH] mm: hugetlb: support get/set_policy for hugetlb_vm_ops

David Hildenbrand <david@...hat.com> 于2022年10月17日周一 16:44写道：
>
> On 12.10.22 10:15, Albert Huang wrote:
> > From: "huangjie.albert" <huangjie.albert@...edance.com>
> >
> > implement these two functions so that we can set the mempolicy to
> > the inode of the hugetlb file. This ensures that the mempolicy of
> > all processes sharing this huge page file is consistent.
> >
> > In some scenarios where huge pages are shared:
> > if we need to limit the memory usage of vm within node0, so I set qemu's
> > mempilciy bind to node0, but if there is a process (such as virtiofsd)
> > shared memory with the vm, in this case. If the page fault is triggered
> > by virtiofsd, the allocated memory may go to node1 which  depends on
> > virtiofsd.
> >
>
> Any VM that uses hugetlb should be preallocating memory. For example,
> this is the expected default under QEMU when using huge pages.
>
> Once preallocation does the right thing regarding NUMA policy, there is
> no need to worry about it in other sub-processes.
>

Hi, David
thanks for your reminder

Yes, you are absolutely right, However, the pre-allocation mechanism
does solve this problem.
However, some scenarios do not like to use the pre-allocation mechanism, such as
scenarios that are sensitive to virtual machine startup time, or
scenarios that require
high memory utilization. The on-demand allocation mechanism may be better,
so the key point is to find a way support for shared policy。

Thanks,

Albert

> --
> Thanks,
>
> David / dhildenb
>