From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dario Faggioli Subject: Re: [PATCH v6 for Xen 4.7 1/4] xen: enable per-VCPU parameter settings for RTDS scheduler Date: Mon, 14 Mar 2016 10:07:33 +0100 Message-ID: <1457946453.3102.633.camel@citrix.com> References: <1457286958-5427-1-git-send-email-lichong659@gmail.com> <1457286958-5427-2-git-send-email-lichong659@gmail.com> <20160308190950.GT31271@citrix.com> <20160310225044.GA25678@citrix.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============7857017002251911761==" Return-path: In-Reply-To: <20160310225044.GA25678@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xen.org Sender: "Xen-devel" To: Wei Liu , Chong Li Cc: Chong Li , Sisu Xi , George Dunlap , xen-devel , Meng Xu , Jan Beulich , Dagaen Golomb List-Id: xen-devel@lists.xenproject.org --===============7857017002251911761== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-uxUSs4sUxgIMPpjo209C" --=-uxUSs4sUxgIMPpjo209C Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2016-03-10 at 22:50 +0000, Wei Liu wrote: > On Thu, Mar 10, 2016 at 04:35:30PM -0600, Chong Li wrote: > > On Tue, Mar 8, 2016 at 1:09 PM, Wei Liu > > wrote: > > > > @@ -1163,6 +1173,96 @@ rt_dom_cntl( > > > >=C2=A0 > > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0/* > > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0* We accept period/budget less than 100 us, but > > > > will warn users about > > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0* the large scheduling overhead due to it > > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0*/ > > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0if ( period < MICROSECS(100) || budget < > > > > MICROSECS(100) ) > > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0printk("Warning: period or budget set to less > > > > than 100us.\n" > > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0"Th= is may result in high scheduling > > > > overhead.\n"); > > > > + > > > I'm not the maintainer, but I think having printk here is bad > > > idea > > > because the toolstack can then DoS the hypervisor. > > >=20 > > >=20 > > > Wei. > > So what function should I use here? I see many LOG() calls in > > libxl, > > but I'm not sure whether that can be used here. > >=20 > IMHO you just don't log anything here. System administrator probably > won't see it anyway. >=20 > If you think this warning is really necessary, move it to xl. >=20 I do think it adds some value to have this. Moving the printing outside of Xen would need exporting a symbol for the minimum budget/period that we think are best chosen, but: =C2=A0- this is really an implementation details, that can (potentially) =C2=A0 =C2=A0vary between different architectures, and change with future X= en=C2=A0 =C2=A0 =C2=A0version; =C2=A0- it would mean to keep the hypervisor and tools symbols in sync.=C2= =A0 So, as I'm saying in another reply in this thread, I'd use a guest, rate-limited, logging variant, and print it only once, as countermeasure to log spamming problem. Regards, Dario --=20 <> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://about.me/dario.faggioli Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK) --=-uxUSs4sUxgIMPpjo209C Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iEYEABECAAYFAlbmf10ACgkQk4XaBE3IOsSJ6gCeLy41S2yAXEVVj8c9wKwj02PF n5sAnjm0QP4u1LjTVtPlyPFF4Jgx/rtw =hl85 -----END PGP SIGNATURE----- --=-uxUSs4sUxgIMPpjo209C-- --===============7857017002251911761== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Content-Disposition: inline X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KWGVuLWRldmVs IG1haWxpbmcgbGlzdApYZW4tZGV2ZWxAbGlzdHMueGVuLm9yZwpodHRwOi8vbGlzdHMueGVuLm9y Zy94ZW4tZGV2ZWwK --===============7857017002251911761==--