git: DragonFly_RELEASE_4_2 kernel - Fix several low memory+swap pageout/killproc issues

[Matthew Dillon]

commit ff93af84bd0bf74c651b67ed2eb537dff2ff412f
Author: Matthew Dillon <dillon at apollo.backplane.com>
Date:   Thu Aug 20 16:45:27 2015 -0700

    kernel - Fix several low memory+swap pageout/killproc issues
    
    * Add significant slop to the PQAVERAGE() calculation in the
      pageout daemon and increase the slop in the vm_paging_target()
      test the pageout daemon makes to determine if it can stop early.
    
      These adjustments fix a degenerate case when no swap is configured
      and a large number of clean pages are present in the inactive queue
      which could prevent the pageout daemon from cleaning a sufficient number
      of pages and cause it to start killing processes even when plenty of
      freeable memory exists.
    
    * Impose a one-second delay when killing processes due to insufficient
      memory + swap.  This reduces the chance that multiple processes will
      be killed even if the first one would have been sufficient by giving
      the kernel more time to dipose of the process.
    
    * Fix a bug in vm_page_alloc().  When v_free_count exactly matches
      v_free_reserved it successfully passes the vm_page_count_target()
      test but vm_page_alloc() will still fail.  This results in a livelock
      in vm_fault_object() and will livelock the pageout daemon vs a user
      process stuck in vm_fault(), causing the machine to lock.
    
      Fixed by adjusting the conditional test in vm_page_alloc().
    
    Reported-by: luxh

Summary of changes:
 sys/vm/vm_page.c    |  7 ++++-
 sys/vm/vm_pageout.c | 74 ++++++++++++++++++++++++++++++++++++++---------------
 2 files changed, 59 insertions(+), 22 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/ff93af84bd0bf74c651b67ed2eb537dff2ff412f


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