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DIR:OUT; SFP:1102; SCL:1; SRVR:DM5PR18MB2231; H:DM5PR18MB1499.namprd18.prod.outlook.com; FPR:; SPF:None; LANG:en; PTR:InfoNoRecords; MX:1; A:1; received-spf: None (protection.outlook.com: suse.com does not designate permitted sender hosts) x-ms-exchange-senderadcheck: 1 x-microsoft-antispam-message-info: /0gin4YYTJ9epmi2bWguS72IhJYyJdW9dO/zvaNSUj1nXPc8VEgv/L9c6gvU8otr/4HvYC1Q2yKnSzcnmkTb8pB/TPKOGX0EpUIsUF3/6SEegOH+0PM9jI10s1NIVeu1Jxx89nhBDwceTpHYmqTyyo9kaAsD+o9QqFXURH/7TLL4o3Qo8e1iMzvPekeELFtzEGpYdCBtmoVS5/qusHDBTO0clpZUufy35zyyM2ZpHWN+VvC5NBz/pPR0WRL9koa4sKH1xZwkGvOxS6QUTAFXTu0sKf+4RjMMTi5SywkDysMPKmeVtAhw8yhd3q+d1XopOpAF2/DE1d+0k0vI/c+l49yeqEDXU9Hv74YyWHkm7d+J9kUKAeVbtG0GoB6rBHOSoSBOdVgFkon4sxig1wpZhFTmD1SPBThFK2UHuAFYW6A= MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 95ebf288-7592-4eb6-625d-08d709fe668e X-MS-Exchange-CrossTenant-originalarrivaltime: 16 Jul 2019 15:00:54.1283 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 856b813c-16e5-49a5-85ec-6f081e13b527 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: dfaggioli@suse.com X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR18MB2231 X-OriginatorOrg: suse.com Subject: Re: [Xen-devel] [PATCH v1 2/5] xen: sched: null: don't assign down vcpus to pcpus X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: "xen-devel@lists.xenproject.org" , "sstabellini@kernel.org" , "roger.pau@citrix.com" Content-Type: multipart/mixed; boundary="===============1841020700517980085==" Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" --===============1841020700517980085== Content-Language: en-US Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="=-vFs/0CZtsKT+s+k4QkBp" --=-vFs/0CZtsKT+s+k4QkBp Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, 2019-07-16 at 12:02 +0000, George Dunlap wrote: > > On Jul 16, 2019, at 11:50 AM, Dario Faggioli > > On Mon, 2019-07-15 at 17:06 +0100, George Dunlap wrote: > > > On 8/25/18 1:21 AM, Dario Faggioli wrote: > > > >=20 > > > The other thing is, from a "developmental purity" point of view, > > > I > > > think > > > this series technically has a regression in the middle: cpu > > > offline / > > > online stops working between patch 2 and patch 4. But I'm > > > inclined > > > in > > > this case not to worry too much. :-) > > >=20 > > Well, the point is that offlining/onlining does not work before > > this > > series. System does not crash, but behavior is wrong, as offline > > vCPUs > > stay assigned to pCPUs (keeping them idle) while online vCPUs are > > "trapped" in the wait list, which is wrong. > >=20 > > So that's why I don't think there's much value in being consistent > > with > > such behavior throughout the series... which I guess is why you > > said > > you "won't worry too much in this case=E2=80=9D ? >=20 > It=E2=80=99s definitely sub-optimal from a system point of view; but from= a > guest point of view, it does (or should) function. Before this > series, if a guest offline and then online vcpus, they should come > back. > Well, yes, I guess they should. IAC, one of the main backing usecases for these fixes is when null is used as the scheduler of the Xen PV- SHIM. In that case, if I remember correctly, the L1 and L2 vCPUs are created offline, and then onlined dynamically. And they don't come up. :-) Anyway... > In the middle of this series, once a vcpu is offlined, it can=E2=80=99t b= e > brought back up. (That is, if I=E2=80=99m reading it right.) > ...Yes, at that stage, things are working even less. But more important... > But I=E2=80=99m not expecting people to be doing bisections of that > particular functionality in this particular scheduler very much. I > think the =E2=80=9Cbenefit=E2=80=9D of avoiding a complicated re-write is= well worth > the =E2=80=9Ccost=E2=80=9D of having that particular bisection fail, on t= he off > chance that anyone tries it. >=20 ...As we fully agree on this, let's move on Regards --=20 Dario Faggioli, Ph.D http://about.me/dario.faggioli Virtualization Software Engineer SUSE Labs, SUSE https://www.suse.com/ ------------------------------------------------------------------- <> (Raistlin Majere) --=-vFs/0CZtsKT+s+k4QkBp Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEES5ssOj3Vhr0WPnOLFkJ4iaW4c+4FAl0t5qQACgkQFkJ4iaW4 c+7xYxAAr/qasXzQfBh+ojowLelHYRHZtC+imF/sLr67eFRPcojFyVOhJ57+dGFL V3VhFEUEn5qax8uszW6T22qWp0jpjac2YdskRwKQfb6n6ZaGMiK5ckyGx9BQqOSU soChYezBJMXHpUrlZNXFQyHjO+//FXRxCiwTg3XL7SWY/HOSE3+35OeqCsS1kq/k nCmzWBZxANbj1VrDfwngmLHoi/MBJxNwJ+eSpQMqZ212N2ADNY94psUHoXRuHu2X bUIuaqVZYHZglbYKNRuh0ab1G6Q87sQQXfW92LWhE5QiNVPz+bKliVRMizXevfFI oL4h97fa375qYRDip0wlFTruqogEYHL61jV4Zn4Jc9eAWKmOTaT5kQMCbvT09y5S LAbnVuH89DDhUQQjrryojuIxVlGMeDal70+fhJqxYcG0y+FfJXbEAaX6uPMtjc0o URhJLin1ZhAGpMldn7E+jxRO6ZZ2bZp1fU7c4rULSq0J1PXYy4xGHuev6vif9QQe MDF7qWRvAQIciOa1n1/H6CjZ108oKNsqOSL6Y8Lkj9EjnTW1kja4EYLjUW/QyvIq n2Ed2aIMPOkyqCDo25dDREimN9q/xT2BQfsdrK19YrLj5KlqSRjmbFxnwUAqMyNb GVUfFkI7P+p4lTXLaQwB4AME5q/luk/mskb1X3sItaBGRWQGrGs= =1j97 -----END PGP SIGNATURE----- --=-vFs/0CZtsKT+s+k4QkBp-- --===============1841020700517980085== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Content-Disposition: inline X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KWGVuLWRldmVs IG1haWxpbmcgbGlzdApYZW4tZGV2ZWxAbGlzdHMueGVucHJvamVjdC5vcmcKaHR0cHM6Ly9saXN0 cy54ZW5wcm9qZWN0Lm9yZy9tYWlsbWFuL2xpc3RpbmZvL3hlbi1kZXZlbA== --===============1841020700517980085==--