--kno3LaHbtea9cJj5CQNI45l6V8XacJLPD Content-Type: multipart/mixed; boundary="xpKKJkTBj1DGO23WMiqFancuNdxdtwPOt"; protected-headers="v1" From: Sven Kieske <s.kieske@mittwald.de> To: devel@ovirt.org Message-ID: <11712170-1758-96b5-adb8-eb29d59be1b8@mittwald.de> Subject: Re: [ovirt-devel] VDSM changes Linux memory dirty ratios - why? References: <CAJgorsbMk1UeLt82GOWsVKOmj=Kse+4CvhoT2E_kj=PUnhG28A@mail.gmail.com> <20161130074847.GA1215@dhcp130-218.brq.redhat.com> <CAJgorsYqRX84st-jByqVbaUHCX=TmtnQeXw1=6FPu_Mbz6kUzg@mail.gmail.com> In-Reply-To: <CAJgorsYqRX84st-jByqVbaUHCX=TmtnQeXw1=6FPu_Mbz6kUzg@mail.gmail.com> --xpKKJkTBj1DGO23WMiqFancuNdxdtwPOt Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable On 30/11/16 09:13, Yaniv Kaul wrote:
Thanks, but it really makes no sense to me. The direct IO by the VMs is=
going to a different storage than what the host is writing to, in most cases. The host would write to the local disk, the VMs - to a shared storage, across NFS or block layer or so. Moreover, their IO is not buffered. There is very little IO coming from the host itself, generally (I hope so!). =20 Partially unrelated - the trend today is actually to put NOOP on the VM= s - the deadline is quite meaningless, as the host scheduler will reschedul= e anyway as it see fits. Most likely it is also a deadline scheduler (but could be NOOP as well = if it's an all flash array, for example). Therefore there is no reason for=
anything but simple NOOP on the VMs themselves. =20 In short, I think it's an outdated decision that perhaps should be revisited. Not urgent, though. Y.
I know it's not the most cared about usecase but I'd like to add that this might affect local storage domains, which I happen to use a lot, and maybe others too. --=20 Mit freundlichen Gr=FC=DFen / Regards Sven Kieske Systemadministrator Mittwald CM Service GmbH & Co. KG K=F6nigsberger Stra=DFe 6 32339 Espelkamp T: +495772 293100 F: +495772 293333 https://www.mittwald.de Gesch=E4ftsf=FChrer: Robert Meyer St.Nr.: 331/5721/1033, USt-IdNr.: DE814773217, HRA 6640, AG Bad Oeynhause= n Komplement=E4rin: Robert Meyer Verwaltungs GmbH, HRB 13260, AG Bad Oeynha= usen --xpKKJkTBj1DGO23WMiqFancuNdxdtwPOt-- --kno3LaHbtea9cJj5CQNI45l6V8XacJLPD Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQIcBAEBAgAGBQJYPsIPAAoJEMby9TMDAbQRCwgQANGx3ttkYz9kbs6x4+vUKiwZ wD3OgXGeqQVoVIJ7H98JgoK3MRbR6EiPJYrx8A/2ROa1k3JCY96wcl1oJwCWQkl6 AXmU/fgqIXCx/8+0CiDU3VtZtlUVHN4Tr0sVpPJ/mH9YdcY6kGj6NA8b9FgeS7IZ DxYDXNyAFLCg6Ei3IFsg0UgIvEZz4ckdDLAVwnWBqIVybY62W96tAH8aghCLNZxz /QnVaW7wOXhZTcMUePGShP2Zy/vW9+P8hzar2ZX4G0Qz86B3lJ6kcFPNuR2D3AIR U2Mx0NRwnCfQXL2Iv1g4LSecwoUZ8qTqnmBE/qjVeGe7kIFD+RfQABPH9+Yj0Fo9 +28rgx049FLI8DPAHPVyxkd2ClLWZ4XpBC0uDvqvzZcFdJ6URAKu+r3y+IM0q6BG CI82Ofv50oXbh1zkWRtzHm/A4tHcIO47WcF55GSgyrdWg1Js7UcFzTuSj9weONVi Af1jsUvjMl1nK98xX8dSXA8qpkAC8V9n/jRd9dIn0bEUkAvQtkkdOzafWkhhvh6r Esj0iKnzGGilx3+wL6AEd/BexIPwp5QrtUHb7EBT7dwOsKfE2mQt2U2WmWE9WWQ4 +eOCYXXIV/za6cUHy/HxQWHv/ByIuGb7BeX1kEaaWjWmfF2JIfWaZnFgi2MD8u/I dgNzTJScMAj6cCK0a1vm =x/5A -----END PGP SIGNATURE----- --kno3LaHbtea9cJj5CQNI45l6V8XacJLPD--