From mboxrd@z Thu Jan 1 00:00:00 1970 From: Simon Valiquette Subject: Re: Query regarding Copy-on-write Date: Mon, 22 Nov 2004 01:31:02 -0500 Message-ID: <41A187A6.4000300@ieee.org> References: <1100947162.4038.43.camel@myLinux> <419F4DA7.1070606@ieee.org> <1101094465.3783.19.camel@myLinux> Mime-Version: 1.0 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-reply-to: <1101094465.3783.19.camel@myLinux> Sender: linux-newbie-owner@vger.kernel.org List-Id: Content-Type: text/plain; charset="iso-8859-1"; format="flowed" To: Linux Newbie Jagadeesh Bhaskar P a =E9crit : > Hi again, > I got the concept. I had no problem understanding the explanation..= =2EI > already knew the concepts of virtual memory and paging so that was no= t a > problem. >=20 > According to ur reply, after the sharing, will always the range of > addresses generated by the process, ie the virtual addresses be the s= ame > of the parent, even if the physical memory pointed to by that is > different. >=20 Yes, otherwise the pointers would point to the wrong adresses and th= e=20 program will probably quickly segfault. > So basically, is it that sharing VM imply that the range of address= es > is shared, and physical pages pointed to by them may or maynot be the > same? >=20 The range of virtual addresses is reused, not shared, but I guess it= =20 is just a question of using the good words (you are probably also a=20 non-native english speakers). But yes that's the basic idea. > Please do help, and thanks for the previous elaborate explanation! >=20 When I first looked inside the Linux kernel, I started by trying to=20 understand how it handled memory. I finally realized how crazy I was,=20 and switched to an easier part. But by the time, I had learned quite a= =20 lot about VM, and also made a minimalist OS for a MC68000 microcontrole= r=20 (only basic process support without even support for a filesystem).=20 That's also probably why I don't think the actual kernel support=20 copy-on-write on MMU-less processor, as I can't think of any good and=20 efficient implementation for that. Simon Valiquette --- The memory management on the PowerPC can be used to frighten small children. - Linus Torvalds - To unsubscribe from this list: send the line "unsubscribe linux-newbie"= in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.linux-learn.org/faqs