Memory de-duplication in the Linux kernel -


Can anyone explain me the algorithm included in memory de-duplication in the Linux kernel

It is difficult to understand and implement it. Can anyone explain this in simple steps?

The article you linked appears to be quite straightforward.

  1. The application advises the kernel (by using madvise () syscall) some areas of that memory may have duplicate pages.
  2. KSMD adds pages in this area to "unstable list" (tree actually, for ease of viewing later). "Volatile" means that pages are still likely to change.
  3. Checksum is calculated in the "volatile" list for each page The code will scan all the pages in the KSMD list and see if the checksum had changed. If it is really different every time, then nothing should be done (the page is still "unstable".)
  4. After the notice of some scanned KSMD , that the checksum page for some particular was stopped changing between iterations (the page was "static"), this "stable" list Can be kept on.
  5. KSMD will scan all existing pages in the "Fixed" list to see if there is already a page that matches the contents of the candidate's page. If such a page is found, then the candidate's page is abandoned, and the current page is read only after the "steady" list (and the relevant reference number for the static page has increased).
  6. If you now find pages in the "Fixed" list, then the candidate page is marked as "Read only" and is moved from "Unstable" to a constant from the list.
  7. If the app will hit a "security error" inside the kernel on the "Fixed" page, invite ksmd to check if the error control page is on the "Stable" list. If so, it will make a written copy of that page and bring it back to the "volatile" list, removes the "static" page from the address of the application and the reference number of the "static" page (if it is counted at this level, "Freeze" page is free).

Comments

Post a Comment

Popular posts from this blog

Java - Error: no suitable method found for add(int, java.lang.String) -

I'm in the middle of homework work and I'm stuck. At this point in my code, I think that I should have a GUI window that opens and allows me to type "inserted text number". Notice is not going anywhere but at this point, If I pass through the problem then it will be in a linked list. I am getting two of the same error for the lines. Add (index, element); And I can not seem to get past it, there is no suitable method for the error "add (int, java. string string)". Code is below, please advise. To clarify - this will not be a method error because it is a linked list. There should not be any way involved. import java.awt. *; Import java.awt.event. *; Import javax.swing. *; Import java.util. *; Import java.util.Scanner; Import java.util.LinkedList; Public class TopTenList JFrame {Private TopTenList tt; See the Private JTextArea list; Private JTextField cmdTextField; Private JTextField resultsTestfield; // This GUI window is the code for the public toptist...
Read more

java - JPA TypedQuery: Parameter value element did not match expected type -

I am using JPA 2.0 and getting the following code in the DAO layer: Public Zero Test () {string key = "status"; String [] Conditions = {"A", "B"}; & Lt; TestTable & gt; Results = Search (Keys, Conditions); } Public listing & lt; TestTable & gt; Search (string key, object value error) {string sql = "test ndf to testlet and jade nand." + Key + "in:" + key; TypedQuery & LT; TestTable & gt; Query = entityManager.createQuery (SQL, TestTable.class); Query.setParameter (key, Arrays.asList (valueArr)) / *** Error Line *** Return query.getResultList (); } In the above error line, it throws the following exception: java.lang.IllegalArgumentException: parameter value element [[Ljava.lang.String; @ cbe5bc] did not match the expected type [java.lang.String] Why is this expected type string while actually this string []? Please help! Note: This is derived from the normal routine and is a simplified code. I can no...
Read more

c++ - static template member variable has internal linkage but is not defined -

Yes, I know, there is a question with almost the same title, but it refers to a different situation. Error message) In my case, I have a .cpp file with a big named designation name (implementation details). There is a property class template with a static data member in that name space, which I need to access from outside the unknown namespace. I give it a little bit of meat: file.hpp namespace Bar {template & lt; Typename A & gt; Struct foo {static_assert (is_same & lt; a, float & gt; :: value} is_same & lt; a, double>: value, ""); Fixed zero set_static_var (a const & x); // ...}; } and file.cpp namespace {template & lt; Typename A & gt; Struct foo_traits {// supports the implementation of several static code bars: foo & lt; & Gt; Fixed A data; }; The template's & lt; & Gt; Float foo_traits & lt; Float & gt; :: datum; // No change if this is in the global namespace template & lt; & Gt; Doub...
Read more