From: Jiri Kosina <jkosina@suse.cz>
To: Xin Tong <xerox.time.tech@gmail.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: linux page table
Date: Sun, 2 Sep 2012 20:26:56 +0200 (CEST) [thread overview]
Message-ID: <alpine.LNX.2.00.1209022026100.20709@pobox.suse.cz> (raw)
In-Reply-To: <CALKntY1XnHG7BAnu4yYU_8iwDttAhuxqu1bBu7YuxXMP4nF+JQ@mail.gmail.com>
On Sun, 2 Sep 2012, Xin Tong wrote:
> >> 3. can two different processes have their CR3 being the same value
> >> even though they have different first level page tables ?
> >
> > Yes, if they are created by clone(CLONE_VM). In such case they share the
> > same mm_struct, and therefore mm_struct->pgd (which is exactly what is
> > loaded into cr3 in switch_mm()) is the same.
> >
>
> Is this the COW mechanism in linux. what if the cloned process need to
> have set of its own pages later. do the CR3s for the 2 processes
> become different at that point ?
That is a different story. COW is applied on fork() (i.e. spawning new
process), not on clone(CLONE_VM) (i.e. spawning new thread).
--
Jiri Kosina
SUSE Labs
next prev parent reply other threads:[~2012-09-02 18:27 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-01 19:30 linux page table Xin Tong
2012-09-01 20:01 ` Shentino
2012-09-01 20:12 ` Xin Tong
2012-09-02 8:10 ` Jiri Kosina
2012-09-02 15:56 ` Xin Tong
2012-09-02 18:26 ` Jiri Kosina [this message]
2012-09-04 8:48 ` Cong Wang
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