From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: On guest free page hinting and OOM Date: Mon, 1 Apr 2019 10:45:21 -0400 Message-ID: <20190401104328-mutt-send-email-mst@kernel.org> References: <20190329084058-mutt-send-email-mst@kernel.org> <20190329104311-mutt-send-email-mst@kernel.org> <7a3baa90-5963-e6e2-c862-9cd9cc1b5f60@redhat.com> <20190329125034-mutt-send-email-mst@kernel.org> <20190401073007-mutt-send-email-mst@kernel.org> <29e11829-c9ac-a21b-b2f1-ed833e4ca449@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Nitesh Narayan Lal , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, pbonzini@redhat.com, lcapitulino@redhat.com, pagupta@redhat.com, wei.w.wang@intel.com, yang.zhang.wz@gmail.com, riel@surriel.com, dodgen@google.com, konrad.wilk@oracle.com, dhildenb@redhat.com, aarcange@redhat.com, alexander.duyck@gmail.com To: David Hildenbrand Return-path: Content-Disposition: inline In-Reply-To: <29e11829-c9ac-a21b-b2f1-ed833e4ca449@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Mon, Apr 01, 2019 at 04:09:32PM +0200, David Hildenbrand wrote: > > > > When you say yield, I would guess that would involve config space access > > to the balloon to flush out outstanding hints? > > I rather meant yield your CPU to the hypervisor, so it can process > hinting requests faster (like waiting for a spinlock). This is the > simple case. More involved approaches might somehow indicate to the > hypervisor to not process queued requests but simply return them to the > guest so the guest can add the isolated pages to the buddy. If this is > "config space access to the balloon to flush out outstanding hints" then > yes, something like that might be a good idea if it doesn't harm > performance. The problem would be in testing this unfortunately. Same as any OOM hack, it is difficult to test well. > -- > > Thanks, > > David / dhildenb