From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40834) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VfuoO-0003Cj-Pe for qemu-devel@nongnu.org; Mon, 11 Nov 2013 11:58:10 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VfuoI-0007NL-Nj for qemu-devel@nongnu.org; Mon, 11 Nov 2013 11:58:04 -0500 Received: from mx1.redhat.com ([209.132.183.28]:56286) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VfuoI-0007My-F3 for qemu-devel@nongnu.org; Mon, 11 Nov 2013 11:57:58 -0500 Received: from int-mx12.intmail.prod.int.phx2.redhat.com (int-mx12.intmail.prod.int.phx2.redhat.com [10.5.11.25]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id rABGvvdx011554 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 11 Nov 2013 11:57:57 -0500 Message-ID: <52810C92.7080500@redhat.com> Date: Mon, 11 Nov 2013 17:57:54 +0100 From: Paolo Bonzini MIME-Version: 1.0 References: <1383840877-2861-1-git-send-email-pbonzini@redhat.com> <20131107162131.GA4370@redhat.com> <527BBFDB.2010404@redhat.com> <20131107164705.GA4572@redhat.com> <527BCE04.9020107@redhat.com> <20131111164309.GA23604@redhat.com> In-Reply-To: <20131111164309.GA23604@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 0/2] exec: alternative fix for master abort woes List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: marcel.a@redhat.com, qemu-devel@nongnu.org, lcapitulino@redhat.com Il 11/11/2013 17:43, Michael S. Tsirkin ha scritto: > On Thu, Nov 07, 2013 at 06:29:40PM +0100, Paolo Bonzini wrote: >> Il 07/11/2013 17:47, Michael S. Tsirkin ha scritto: >>> That's on kvm with 52 bit address. >>> But where I would be concerned is systems with e.g. 36 bit address >>> space where we are doubling the cost of the lookup. >>> E.g. try i386 and not x86_64. >> >> Tried now... >> >> P_L2_LEVELS pre-patch post-patch >> i386 3 6 >> x86_64 4 6 >> >> I timed the inl_from_qemu test of vmexit.flat with both KVM and TCG. With >> TCG there's indeed a visible penalty of 20 cycles for i386 and 10 for x86_64 >> (you can extrapolate to 30 cycles for TARGET_PHYS_ADDR_SPACE_BITS=32 targets). > > So how did you measure this exactly? I mention extrapolation because x86 is TARGET_PHYS_ADDR_SPACE_BITS=36, not 32. Paolo