From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:51701)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1Viiq2-0007cg-5v
	for qemu-devel@nongnu.org; Tue, 19 Nov 2013 05:47:28 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1Viipw-0002RE-4A
	for qemu-devel@nongnu.org; Tue, 19 Nov 2013 05:47:22 -0500
Received: from mx1.redhat.com ([209.132.183.28]:21358)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1Viipv-0002Qy-RK
	for qemu-devel@nongnu.org; Tue, 19 Nov 2013 05:47:16 -0500
Message-ID: <528B41A5.1080504@redhat.com>
Date: Tue, 19 Nov 2013 11:47:01 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
MIME-Version: 1.0
References: <1379694292-1601-1-git-send-email-pbonzini@redhat.com>	<1379694292-1601-12-git-send-email-pbonzini@redhat.com>
	<528A310A.60607@dlhnet.de> <528A3422.1030701@kamp.de>
	<528A3C4A.4090001@redhat.com> <528B3C86.3030309@kamp.de>
In-Reply-To: <528B3C86.3030309@kamp.de>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [PULL 11/13] target-i386: forward CPUID cache
 leaves when -cpu host is used
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Peter Lieven <pl@kamp.de>
Cc: qemu-devel@nongnu.org, Anthony Liguori <anthony@codemonkey.ws>, =?UTF-8?B?QmVub8OudCBDYW5ldA==?= <benoit@irqsave.net>

Il 19/11/2013 11:25, Peter Lieven ha scritto:
>>
> 
> ~/git/qemu$ x86_64-softmmu/qemu-system-x86_64 -m 2048 -drive
> if=virtio,file=iscsi://172.21.200.45/iqn.2001-05.com.equallogic:0-8a0906-9d95c510a-344001d54795289f-2012-r2-1-7-0/0,format=raw,cache=writeback,aio=native
> -smp 2,cores=2,threads=1,sockets=1 -cpu host -monitor stdio -vnc :1
> -enable-kvm -usb -usbdevice tablet -vga cirrus -global
> virtio-blk-pci.scsi=off  -serial null  -parallel null -boot c

What is your host CPU's topology

> With just -smp 2 it works. However, have a look at my other email I
> think there is a bug in smp_parse, because -smp 2 yields
> cpus=2,cores=1,threads=1,sockets=1 whereas I think cores should
> be 2.

The code matching the comment in vl.c ("compute missing values, prefer
sockets over cores over threads") would be like "-smp
cpu=2,cores=1,threads=1,sockets=2", giving this code:

        if (cpus == 0) {
            sockets = sockets > 0 ? sockets : 1;
            cores = cores > 0 ? cores : 1;
            threads = threads > 0 ? threads : 1;
            cpus = cores * threads * sockets;
        } else if (sockets == 0) {
            cores = cores > 0 ? cores : 1;
            threads = threads > 0 ? threads : 1;
            sockets = cpus / (cores * threads);
        } else if (cores == 0) {
            threads = threads > 0 ? threads : 1;
            cores = cpus / (sockets * threads);
        } else {
            threads = cpus / (sockets * cores);
        }

What you suggest is cores over threads over sockets:

        if (cpus == 0) {
            cores = cores > 0 ? cores : 1;
            threads = threads > 0 ? threads : 1;
            sockets = sockets > 0 ? sockets : 1;
            cpus = cores * threads * sockets;
        } else if (cores == 0) {
            threads = threads > 0 ? threads : 1;
            sockets = sockets > 0 ? sockets : 1;
            cores = cpus / (threads * sockets);
        } else if (threads == 0) {
            sockets = sockets > 0 ? sockets : 1;
            threads = cpus / (cores * sockets);
        } else {
            sockets = cpus / (cores * threads);
        }

Can you test which of these two work?  But I agree it's best to disable
cache-leaf forwarding.

Paolo