ADSM-L

Re: [ADSM-L] AIX large pages with TSM

2015-03-12 07:20:31
Subject: Re: [ADSM-L] AIX large pages with TSM
From: "Rhodes, Richard L." <rrhodes AT FIRSTENERGYCORP DOT COM>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Thu, 12 Mar 2015 11:18:39 +0000
>Later versions of AIX have two larger page sizes available and so the
>number of locks to be taken and released drops dramatically for the
>typical 256KB tape transfer.

This is what I'm really confused about, and our AIX admins don't have an answer.
Our Power systems with AIX supports 4k, 64k and 16mb pages.  The IBM 
presentation makes the case about minimizing lock contation b using 16mb 
non-pagable pages.  But it also notes that using 64k pages can greatly minimize 
the contention.  When I check svmon, most of our BSS heap segments are already  
using both small(4k) and medium(64k) pages  (the "sm" in the listing below).

  svmon -P 10944554 | grep -i "bss heap"
    d811d8        12 work text data BSS heap          sm  57518     0    0   
57518
    ab892b        13 work text data BSS heap          sm  48006     0    0   
48006
    f8317a        14 work text data BSS heap          sm  37204     0    0   
37204
    bc0f3c        11 work text data BSS heap          sm  34200     0    0   
34200
    f50e75        10 clnt text data BSS heap,          s  28667     0    -      
 -
    991d9b        15 work text data BSS heap          sm  26213     0    0   
26213
    9e279c        16 work text data BSS heap          sm   9023     0    0    
9023
    92d013        17 work text data BSS heap          sm   3652     0    0    
3652

I don't see any way to tell if the I/O is locking 4k pages, 64k pages, or a 
mix.  The presentation gave 2 different LDR_CNTRL variables depending upon if 
you want 16mb pages or 64k pages.  

  16mb pages:   
LDR_CNTRL=TEXTPSIZE=64K@STACKPSIZE=64K@SHMPSIZE=64K@LARGE_PAGE_DATA=Y     
dsmserv
  64k pages:    
LDR_CNTRL=TEXTPSIZE=64K@STACKPSIZE=64K@SHMPSIZE=64K@DATAPSIZE=64K         
dsmserv

My assumption is that the 64k LDR_CNTRL will make all the BSS heaps use only 
64k pages.  
I'm tempted to try this first since it doesn't require an AIX reboot, just a 
TSM shutdown/startup.


Rick


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