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From: Alan Cox <alc@FreeBSD.org>
Date: Sat, 17 Apr 2010 18:35:07 +0000 (UTC)
To: cvs-src-old@freebsd.org
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Subject: cvs commit: src/sys/vm vm_object.c
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alc         2010-04-17 18:35:07 UTC

  FreeBSD src repository

  Modified files:
    sys/vm               vm_object.c 
  Log:
  SVN rev 206768 on 2010-04-17 18:35:07Z by alc
  
  In vm_object_backing_scan(), setting PG_REFERENCED on a page before
  sleeping on that page is nonsensical.  Doing so reduces the likelihood
  that the page daemon will reclaim the page before the thread waiting in
  vm_object_backing_scan() is reawakened.  However, it does not guarantee
  that the page is not reclaimed, so vm_object_backing_scan() restarts
  after reawakening.  More importantly, this muddles the meaning of
  PG_REFERENCED.  There is no reason to believe that the caller of
  vm_object_backing_scan() is going to use (i.e., access) the contents of
  the page.  There is especially no reason to believe that an access is
  more likely because vm_object_backing_scan() had to sleep on the page.
  
  Discussed with: kib
  MFC after:      3 weeks
  
  Revision  Changes    Path
  1.410     +0 -3      src/sys/vm/vm_object.c