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SubjectRe: 2.4.19 Vs 2.4.19-rmap14a with anonymous mmaped memory
On Thu, 29 Aug 2002, Daniel Phillips wrote:

> The perl script that writes tables isn't too informative without knowing
> how the tables are used. Pseudocode that says exactly what your final
> reference pattern is would be a lot more useful.

I guessed that after I thought about it for a while and reworked the
algorithm for 0.7. To make things easier again, I added a new graph to the
reports which is in 0.7 called "Page Index Reference over Time"

see

http://www.csn.ul.ie/~mel/projects/vmregress/output_sample/mmap/read/25000/mapanon.html

It is the second graph. At the beginning, it is at the 0th page and it
moves through the address space over time. A totally random one would make
this graph look like noise. The graph should give a good idea how memory
was referenced.

In 0.6 and with these tests, it would have been a similar curve except the
last page would have been hit around 40000 references before the end of
the test. After that, the pages were referenced in a linear pattern which
was a mistake after reviewing it a bit.

If people are still interested, I'll run a full set of tests again on
2.4.19 and 2.4.19-rmap14a with 0.7 and post up the results complete with
the page reference information so you don't have to guess this time. It
takes about a full day to run a complete series. Any taker?

> It would also be useful to state what you define as a reference. A user
> space program read-accesses a single byte from some address?
>

A reference in this test was reading a full page of information using
copy_from_user()

--
Mel Gorman
MSc Student, University of Limerick
http://www.csn.ul.ie/~mel

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