cvs commit: src/sys/vm vm_page.c

Poul-Henning Kamp phk at
Fri Jun 6 23:27:50 UTC 2008

In message <4849C2D0.9060704 at>, Alan Cox writes:
>Poul-Henning Kamp wrote:

>>>  Essentially, neither madvise(..., MADV_DONTNEED) nor madvise(..., MADV_FREE)
>>>  work.  (Moreover, I don't believe that they have ever worked as intended.)
>> I remember they did have a measurable but minor impact on performance
>> in systems which paged a lot, back when they were introduced, sort
>> of 1995-ish.  But with the subsequent plunge in RAM prices they
>> never saw much use.
>After more thorough digging through CVS history, I now believe that 
>MADV_DONTNEED worked properly between revision 1.70 (May 1996) and 1.76 
>(June 1996) of vm/vm_object.c.  :-)  It's more difficult to say for 
>MADV_FREE.  It may have been effective until 1999.

Sounds quite probable.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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