From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1754000AbcLQHeP (ORCPT <rfc822;w@1wt.eu>);
        Sat, 17 Dec 2016 02:34:15 -0500
Received: from asavdk4.altibox.net ([109.247.116.15]:37107 "EHLO
        asavdk4.altibox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751252AbcLQHeO (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Sat, 17 Dec 2016 02:34:14 -0500
Date: Sat, 17 Dec 2016 08:34:06 +0100
From: Sam Ravnborg <sam@ravnborg.org>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: sparclinux@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, "David S . Miller" <davem@davemloft.net>,
        Bob Picco <bob.picco@oracle.com>,
        Nitin Gupta <nitin.m.gupta@oracle.com>,
        Vijay Kumar <vijay.ac.kumar@oracle.com>,
        Julian Calaby <julian.calaby@gmail.com>,
        Adam Buchbinder <adam.buchbinder@gmail.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Michal Hocko <mhocko@suse.com>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC PATCH 02/14] sparc64: add new fields to mmu context for
 shared context support
Message-ID: <20161217073406.GA23567@ravnborg.org>
References: <1481913337-9331-1-git-send-email-mike.kravetz@oracle.com>
 <1481913337-9331-3-git-send-email-mike.kravetz@oracle.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1481913337-9331-3-git-send-email-mike.kravetz@oracle.com>
User-Agent: Mutt/1.5.21 (2010-09-15)
X-CMAE-Score: 0
X-CMAE-Analysis: v=2.2 cv=eqGd9chX c=1 sm=1 tr=0
        a=Ij76tQDYWdb01v2+RnYW5w==:117 a=Ij76tQDYWdb01v2+RnYW5w==:17
        a=kj9zAlcOel0A:10 a=F9h01uA4jUlDOgSwivgA:9 a=CjuIK1q_8ugA:10
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hi Mike.

On Fri, Dec 16, 2016 at 10:35:25AM -0800, Mike Kravetz wrote:
> Add new fields to the mm_context structure to support shared context.
> Instead of a simple context ID, add a pointer to a structure with a
> reference count.  This is needed as multiple tasks will share the
> context ID.

What are the benefits with the shared_mmu_ctx struct?
It does not save any space in mm_context_t, and the CPU only
supports one extra context.
So it looks like over-engineering with all the extra administration
required to handle it with refcount, poitners etc.

what do I miss?

	Sam