From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53932) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cxvob-0008Oh-1o for qemu-devel@nongnu.org; Tue, 11 Apr 2017 09:26:38 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cxvoX-0002Tk-U8 for qemu-devel@nongnu.org; Tue, 11 Apr 2017 09:26:37 -0400 Message-ID: <1491917167.7236.1.camel@kernel.crashing.org> From: Benjamin Herrenschmidt Date: Tue, 11 Apr 2017 23:26:07 +1000 In-Reply-To: <04c9f03f-7f04-ebce-15f1-988db1fb2c1d@kaod.org> References: <20170406102249.20383-1-nikunj@linux.vnet.ibm.com> <6029cef4-0a41-cde0-b3c9-6b6ad9bde572@kaod.org> <87vaqgrds2.fsf@abhimanyu.i-did-not-set--mail-host-address--so-tickle-me> <25dcb89b-35be-ea27-8719-7b446f464694@kaod.org> <87lgr8ji2f.fsf@linaro.org> <04c9f03f-7f04-ebce-15f1-988db1fb2c1d@kaod.org> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [Qemu-ppc] [PATCH RFC v1 0/3] Enable MTTCG on PPC64 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: =?ISO-8859-1?Q?C=E9dric?= Le Goater , Alex =?ISO-8859-1?Q?Benn=E9e?= Cc: Nikunj A Dadhania , qemu-ppc@nongnu.org, david@gibson.dropbear.id.au, rth@twiddle.net, programmingkidx@gmail.com, qemu-devel@nongnu.org, bharata@linux.vnet.ibm.com On Tue, 2017-04-11 at 14:28 +0200, C=C3=A9dric Le Goater wrote: > I really don't know.=C2=A0 >=20 > Ben, now that we have mttcg activated by default on ppc, it takes=C2=A0 > a while for the linux kernel to do the early setup. I think we are > in the code section where we spin loop the secondaries. Most of the > time is spent in skiboot under cpu_idle/relax. >=20 > Any idea where that could come from ?=C2=A0 >=20 > > See c22edfebff29f63d793032e4fbd42a035bb73e27 for an example. >=20 > Thanks for the hint. They are spinning, but they have smt_low instructions in the loop, maybe that causes us to do some kind of synchronization as we exit the emulation loop on these ? I added that to force relinguish time to other threads on the pre-MT TCG... There isn't really such a "pause" instruction. At least not yet.... P9 has a wait that is meant to wait for special AS_Notify cycles but will also wait for interrupts. We don't have an mwait at this point. Ben. =20