linux-kernel - RE: [RFC][Patch v8 0/7] KVM: Guest Free Page Hinting

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Message-ID: <286AC319A985734F985F78AFA26841F73DF71F38@shsmsx102.ccr.corp.intel.com>
Date:   Fri, 15 Feb 2019 09:05:10 +0000
From:   "Wang, Wei W" <wei.w.wang@...el.com>
To:     'David Hildenbrand' <david@...hat.com>,
        'Nitesh Narayan Lal' <nitesh@...hat.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "lcapitulino@...hat.com" <lcapitulino@...hat.com>,
        "pagupta@...hat.com" <pagupta@...hat.com>,
        "yang.zhang.wz@...il.com" <yang.zhang.wz@...il.com>,
        "riel@...riel.com" <riel@...riel.com>,
        "mst@...hat.com" <mst@...hat.com>,
        "dodgen@...gle.com" <dodgen@...gle.com>,
        "konrad.wilk@...cle.com" <konrad.wilk@...cle.com>,
        "dhildenb@...hat.com" <dhildenb@...hat.com>,
        "aarcange@...hat.com" <aarcange@...hat.com>
Subject: RE: [RFC][Patch v8 0/7] KVM: Guest Free Page Hinting

On Thursday, February 14, 2019 5:43 PM, David Hildenbrand wrote:
> Yes indeed, that is the important bit. They must not be put pack to the
> buddy before they have been processed by the hypervisor. But as the pages
> are not in the buddy, no one allocating a page will stumble over such a page
> and try to allocate it. Threads trying to allocate memory will simply pick
> another buddy page instead of "busy waiting" for that page to be finished
> reporting.

What if a guest thread try to allocate some pages but the buddy cannot satisfy
because all the pages are isolated? Would it be the same case that the guest thread
gets blocked by waiting all the isolated pages to get madvised by the host and
returned to the guest buddy, or even worse, some guest threads get killed due to oom?

Best,
Wei