On Wed, Dec 07, 2005 at 11:30:44AM +0100, Emmanuel Colbus wrote: > Jonathan S. Shapiro a ?crit : > > If two applications are sharing a pool, they are already in direct > > communication, and considerations of covert channels become irrelevant. ... > > The thing we are sharing may be read-only. Adding the requirement for a > > shared mutable region causes it to become read-write, and therefore a > > communication channel.
Mind if I consider this a contradiction? I agree with the second statement though. > It uses the "accessed" bit in the page table entry : if it is 0, the page > hasn't been accessed since the last time the keeper set it to 0, so its new > age is "previous age + 1 keeper cycle time"; if it is 1, its new age is 0. > At page arrival, "previous age" is set to 0 (or was set to 0 for long, > because it is also the value for unused pages); but the keeper can't > differentiate such a page from a recently accessed one. This sounds like a very processor-intensive method for something which can be notification-based. When it's notification-based, the keeper can simply go to sleep until something interesting happens (e.g. a page fault). In this system it's active all the time (well, it sleeps in between, but it will definitely never be swapped out for long). That is a Bad Thing IMO. Thanks, Bas -- I encourage people to send encrypted e-mail (see http://www.gnupg.org). If you have problems reading my e-mail, use a better reader. Please send the central message of e-mails as plain text in the message body, not as HTML and definitely not as MS Word. Please do not use the MS Word format for attachments either. For more information, see http://129.125.47.90/e-mail.html
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