linux-kernel - Re: [RFC][Patch v9 2/6] KVM: Enables the kernel to isolate guest free pages

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Date:   Thu, 7 Mar 2019 21:32:07 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Alexander Duyck <alexander.duyck@...il.com>
Cc:     David Hildenbrand <david@...hat.com>,
        Nitesh Narayan Lal <nitesh@...hat.com>,
        kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>,
        Paolo Bonzini <pbonzini@...hat.com>, lcapitulino@...hat.com,
        pagupta@...hat.com, wei.w.wang@...el.com,
        Yang Zhang <yang.zhang.wz@...il.com>,
        Rik van Riel <riel@...riel.com>, dodgen@...gle.com,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        dhildenb@...hat.com, Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [RFC][Patch v9 2/6] KVM: Enables the kernel to isolate guest
 free pages

On Thu, Mar 07, 2019 at 02:35:53PM -0800, Alexander Duyck wrote:
> The only other thing I still want to try and see if I can do is to add
> a jiffies value to the page private data in the case of the buddy
> pages.

Actually there's one extra thing I think we should do, and that is make
sure we do not leave less than X% off the free memory at a time.
This way chances of triggering an OOM are lower.

> With that we could track the age of the page so it becomes
> easier to only target pages that are truly going cold rather than
> trying to grab pages that were added to the freelist recently.

I like that but I have a vague memory of discussing this with Rik van
Riel and him saying it's actually better to take away recently used
ones. Can't see why would that be but maybe I remember wrong. Rik - am I
just confused?


-- 
MST