cvs commit: src/sys/vm vm_page.c

Alan Cox alc at
Fri Jun 6 23:25:46 UTC 2008

Poul-Henning Kamp wrote:
> In message <200806061838.m56Icu2E074642 at>, Alan Cox writes:
>> alc         2008-06-06 18:38:43 UTC
>>  FreeBSD src repository
>>  Modified files:
>>    sys/vm               vm_page.c 
>>  Log:
>>  SVN rev 179623 on 2008-06-06 18:38:43Z by alc
>>  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.


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