Re: [Gems-users] Page Fault in Ruby


Date: Thu, 08 Jun 2006 12:33:01 -0400
From: Mrinmoy Ghosh <mrinmoy@xxxxxxxxxxxxxx>
Subject: Re: [Gems-users] Page Fault in Ruby
Hi Dan,
Thanks for your answer. I was enquiring about page faults in the target or the simlated virtual machine. I have one small question. Since you say here that Ruby is not aware of Paging, I think you mean the following. Please correct me if I am wrong.

It is the responsibility of the TLB fault handler to check the page table in memory and check for page faults. If a page table entry is nulll the page fault handler is invoked and the page is brought in from the disk. As far as Ruby is concerned, it assumes that any request sent to it from the caches will always be present, as it would have been handled by the page fault handler before.

Please let me know if I am clear in my understanding of this.

Mrinmoy
Dan Gibson wrote:

Hi Mrinmoy,

Would you be referring to page faults on the host machine, or page faults on the target machine?

For the former:
Ruby queries its host machine when stats are dumped for the number of page faults encoutered during simulation, but it is not "aware" of a page fault on its host as it occurs.

For the latter:
Ruby is not directly aware of paging activity on its target. Since paging is a system-level phenomenon, you might be able to caputre paging with a Simics hap callback (see the Simics Reference Manual and the Simics Programming Guide for details), or possibly by observing the dynamic instruction stream and signaling when a parcicular physical PC is reached.

Regards,
Dan Gibson

Mrinmoy Ghosh wrote:

Hi,
I was interested to know, if ruby memory module signals Page Faults, and if yes, some pointers in the code as to how or where this is done.

Mrinmoy

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