linux-kernel - Re: [PATCH v34 0/4] Virtio-balloon: support free page reporting

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Date:   Fri, 29 Jun 2018 18:03:09 +0200
From:   David Hildenbrand <david@...hat.com>
To:     "Wang, Wei W" <wei.w.wang@...el.com>,
        "virtio-dev@...ts.oasis-open.org" <virtio-dev@...ts.oasis-open.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "mst@...hat.com" <mst@...hat.com>,
        "mhocko@...nel.org" <mhocko@...nel.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Cc:     "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "liliang.opensource@...il.com" <liliang.opensource@...il.com>,
        "yang.zhang.wz@...il.com" <yang.zhang.wz@...il.com>,
        "quan.xu0@...il.com" <quan.xu0@...il.com>,
        "nilal@...hat.com" <nilal@...hat.com>,
        "riel@...hat.com" <riel@...hat.com>,
        "peterx@...hat.com" <peterx@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Luiz Capitulino <lcapitulino@...hat.com>
Subject: Re: [PATCH v34 0/4] Virtio-balloon: support free page reporting


>> Why would your suggestion still be applicable?
>>
>> Your point for now is "I might not want to have page hinting enabled due to
>> the overhead, but still a live migration speedup". If that overhead actually
>> exists (we'll have to see) or there might be another reason to disable page
>> hinting, then we have to decide if that specific setup is worth it merging your
>> changes.
> 
> All the above "if we have", "assume we have" don't sound like a valid argument to me.

Argument? *confused* And that hinders you from answering the question
"Why would your suggestion still be applicable?" ? Well, okay.

So I will answer it by myself: Because somebody would want to disable
page hinting. Maybe there are some people out there.

>  
>> I am not (and don't want to be) in the position to make any decisions here :) I
>> just want to understand if two interfaces for free pages actually make sense.
> 
> I responded to Nitesh about the differences, you may want to check with him about this.
> I would suggest you to send out your patches to LKML to get a discussion with the mm folks.

Indeed, Nitesh is trying to solve the problems we found in the RFC, so
this can take some time.

> 
> Best,
> Wei
> 


-- 

Thanks,

David / dhildenb