linux-kernel - Re: [PATCH] mm: don't zero ballooned pages

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Date:   Mon, 31 Jul 2017 09:43:50 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Wei Wang <wei.w.wang@...el.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        virtualization@...ts.linux-foundation.org, mst@...hat.com,
        mawilcox@...rosoft.com, dave.hansen@...el.com,
        akpm@...ux-foundation.org, zhenwei.pi@...runcloud.com
Subject: Re: [PATCH] mm: don't zero ballooned pages

On Mon 31-07-17 15:41:49, Wei Wang wrote:
> On 07/31/2017 02:55 PM, Michal Hocko wrote:
> >On Mon 31-07-17 12:13:33, Wei Wang wrote:
> >>Ballooned pages will be marked as MADV_DONTNEED by the hypervisor and
> >>shouldn't be given to the host ksmd to scan.
> >Could you point me where this MADV_DONTNEED is done, please?
> 
> Sure. It's done in the hypervisor when the balloon pages are received.
> 
> Please see line 40 at
> https://github.com/qemu/qemu/blob/master/hw/virtio/virtio-balloon.c

Thanks. Are all hypervisors which are using this API doing this?
bb01b64cfab7 doesn't mention the specify hypervisor nor does it mention
any real numbers so I suspect the revert is the right thing to do but
the changelog should mention all those details.
-- 
Michal Hocko
SUSE Labs