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

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Message-ID: <e13bd5e9-981f-e2f1-fdd9-049a1926d70f@oracle.com>
Date:   Thu, 2 Dec 2021 09:27:17 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     David Hildenbrand <david@...hat.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 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.
-- 
Mike Kravetz