[GRASS-dev] [GRASS GIS] #1625: Disk performance degrades by several orders of magnitude on two processes

[GRASS GIS]

#1625: Disk performance degrades by several orders of magnitude on two processes
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 Reporter:  sprice   |       Owner:  grass-dev@…              
     Type:  defect   |      Status:  new                      
 Priority:  normal   |   Milestone:  7.0.0                    
Component:  Default  |     Version:  svn-trunk                
 Keywords:           |    Platform:  MacOSX                   
      Cpu:  x86-64   |  
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 When there are two GRASS process competing for a single disk on an I/O
 bound task, performance doesn't just half. It decreases by several orders
 of magnitude. However, 'iostat' lists just as much data flowing off the
 disk as would be expected.

 Also, when one task is canceled, the other process doesn't recover.
 'iostat' claims that just as much data is flowing, but the remaining
 process remains degraded until it is canceled and restarted.

 I'd try to give a bit more debug info, but I suspect that it's some sort
 of interaction with a caching layer in GRASS where extra data is read, and
 then discarded, many times.

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Ticket URL: <http://trac.osgeo.org/grass/ticket/1625>
GRASS GIS <http://grass.osgeo.org>