kern/38270: spurious OOM due to trylock

[yamt%mwd.biglobe.ne.jp@localhost]

>Number:         38270
>Category:       kern
>Synopsis:       spurious OOM due to trylock
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Mar 21 06:00:01 +0000 2008
>Originator:     YAMAMOTO Takashi <yamt%mwd.biglobe.ne.jp@localhost>
>Release:        NetBSD 4.99.55
>Organization:
        
>Environment:
Architecture: i386
Machine: i386
>Description:
        consider that we have enough free pages but little swap.
        1. uvm_analloc fails due to vm_map trylock failure.
        2. uvm_reclaimable returns false.  while we have plenty of
           free pages, it doesn't mean we have reclaimable pages.
        3. now the faulting process dies saying out of swap.
>How-To-Repeat:
        
>Fix:
        kill trylock.
        or don't assume that uvm_analloc failure is always due to
        memory shortage.

>Unformatted: