From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:55736) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1R8qXS-0006u2-IT for qemu-devel@nongnu.org; Wed, 28 Sep 2011 05:34:54 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1R8qXJ-0003er-Db for qemu-devel@nongnu.org; Wed, 28 Sep 2011 05:34:50 -0400 Received: from mail-bw0-f45.google.com ([209.85.214.45]:34509) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1R8qXJ-0003eX-3n for qemu-devel@nongnu.org; Wed, 28 Sep 2011 05:34:41 -0400 Received: by bkbzv15 with SMTP id zv15so8118953bkb.4 for ; Wed, 28 Sep 2011 02:34:39 -0700 (PDT) Date: Wed, 28 Sep 2011 11:34:33 +0200 From: "Edgar E. Iglesias" Message-ID: <20110928093433.GA13116@edde.se.axis.com> References: <86ty7xfr7c.fsf@shell.gmplib.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <86ty7xfr7c.fsf@shell.gmplib.org> Subject: Re: [Qemu-devel] Qemu varying performance List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Torbjorn Granlund Cc: qemu-devel@nongnu.org On Wed, Sep 28, 2011 at 02:25:43AM +0200, Torbjorn Granlund wrote: > Running Debian's vmlinux-2.6.32-5-4kc-malta under qemu-system-mips works > very well--the system is fast, and when it is idle the qemu-system-mips > process on the host system consumes insignificant CPU. (The same is > true for qemu-system-mipsel, using the correesponding 'el' Debian > kernel.) > > But running Debian's 64-bit kernel vmlinux-2.6.32-5-5kc-malta under > qemu-system-mips64 consumes 100% on the host system, whether the guest > is idle or busy. (And for qemu-system-mips64el, the same is true for the > corresponding 64-bit el kernel.) > > This cpu usage makes it somewhat inconvenient to let the qemu processes > stay running. Is there anything that can be done about the cpu usage? > Is it a Linux problem (say, that the 64-bit kernel fails to invoke some > clever system sleep instruction when in the idle loop), or is it a qemu > problem? Hi, It could be any of them or both. You'll have to dig a bit deeper and see if WAIT insns are beeing issued and if QEMU is successfully decoding them etc. > Another issue I ran into what the sh4 qemu performance. It is much > worse than other qemu ports (except perhaps ppc64). What is the reason > behind that? (The idle thing works well for sh4, though.) IIRC, the SH has an MMU that is a bit problematic wrt performance in QEMU. Cheers