linux-kernel - Re: [RFD] clear virtual machine memory when virtual machine is turned off

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Message-ID: <1e0ce8f6-332b-399f-5ac7-5a56639172b3@redhat.com>
Date:   Fri, 3 Dec 2021 19:20:45 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>,
        fei luo <morphyluo@...il.com>, akpm@...ux-foundation.org,
        arnd@...db.de, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org
Cc:     Joao Martins <joao.m.martins@...cle.com>
Subject: Re: [RFD] clear virtual machine memory when virtual machine is turned
 off

On 02.12.21 18:27, Mike Kravetz wrote:
> On 12/2/21 04:47, David Hildenbrand wrote:
>> On 02.12.21 11:19, fei luo wrote:
>>>
>>> When reusing the page that has been cleared, there is no need to clear it
>>>
>>> again, which also speeds up the memory allocation of user-mode programs.
>>>
>>>
>>> Is this feature feasible?
>>
>> "init_on_free=1" for the system as a whole, which might sounds like what
>> might tackle part of your use case.
>>
> 
> Certainly init_on_free will not make much difference if VMs are backed by
> hugetlb pages.  We (Joao and myself) have thought about clearing hugetlb
> pages from user space in an attempt speed up launching of VMs backed by
> hugetlb pages.
> 

I remember that discussion. And I also recall a discussion regarding
extending init_on_free semantics to hugetlbfs.

-- 
Thanks,

David / dhildenb