DOCUMENT VMINFO.H FIELD PGEXCT

ITEM: RTA000053036

QUESTION:                                                                       
Our locally written performance monitor is displaying the pgexct                
field of struct vminfo from the /usr/include/sys/vminfo.h                       
header file.  The comment for this field is "count of page faults"              
and it's value is the same as the faults/s column of sar -r.                    
We have verified through several sources that our local tool is not             
displaying bogus information-that it is in fact the value in that field         
in the kernel.  Can you provide a detailed description of the meaning of        
pgexct field and the faults/s column of sar?                                    
                                                                                
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A: This variable is reported in "vmstat -s" as                                  
   "total address translation faults".                                          
   This counter would be increased every time the system goes                   
   to read a page from memory and the page is not in memory,                   
   for whatever reason.  Sometimes this page fault can be resolved              
   without an I/O:  If another process has used this page and then              
   released it, it can be "reclaimed" for use by the next process.              
   The address translation is counted in this variable, but                     
   the I/O to bring in the page from disk is not needed.                        
                                                                                
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This item was created from library item Q676740      CKRLG                      
                                                                                
Additional search words:                                                        
CKRLG DEC94 DOCUMENT DOCUMENTATIO FIELD IX MEASURE OP OZIBM OZNEW               
PERFORMANCE PGEXCT RISCPERF RISCSYSTEM SOFTWARE SYS TEXT TUNE                   
VMINFO.H                                                                       



WWQA: ITEM: RTA000053036 ITEM: RTA000053036

Dated: 03/1996 Category: RISCPERF

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