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Programming Interface Information:
This information is NOT intended to be used as Programming Interfaces of z/VM. |
DSCBK
Control Block Contents
DSCBK DSECT
Cross Reference (Contains links to field and bit definitions)
DSCBK Prolog
NAME : HCPDSCBK
Description: Demand Scan Control Block
DSECT : DSCBK
Function :
The Demand Scan Control Block (DSCBK) contains
information about the Available List Demand Scan
operation. The DSCBK is persistent and some
information is saved between Demand Scans.
Created by : Assembly at Entry Point HCPRSMSC.
Deleted by : none
DSCBK Control Block Content
DSCBK DSECT
Hex Dec Type/Val Lng Label (dup) Comments ---- ---- --------- ---- -------------- -------- 0000 0 Structure DSCBK Demand Scan Control Block 0000 0 Signed 4 DSCWORD (0) Demand Scan Status Word 0000 0 Bitstring 1 DSCPROG Indicate Demand Scan Progress 1... .... DSCPASS1 X'80' Working on the first pass .1.. .... DSCPASS2 X'40' Working on the second pass ..1. .... DSCEMRGP X'20' Working on EMERGENCY pass ...1 .... DSCLTD X'10' Working on a user from the Long-Term Dormant List .... 1... DSCLTDHX X'08' This scan ended on a user from the Long-Term Dormant List .... .1.. DSCDLSCN X'04' Scanning the Dormant List .... ..1. DSCTKALL X'02' Took ALL possible frames from the Dormant List VMDBK base address space (except locked or reserved frames). .... ...1 DSCA2GPP X'01' Stealing >=2G frames to relieve <2G resident pageable PGMBK pressure. Causes steal of >= 2G frames to begin / continue even if there is no >=2G system need (DSCREQDG=0) 0001 1 Bitstring 1 DSCLKFLG Contains only lock status and is cleared in RELLOCKS subroutine in module HCPALS. 1... .... DSCPTILK X'80' Demand Scan owns the Page Table Lock (VMDPTIL) now. .1.. .... DSCPTIL2 X'40' Indicate we obtained VMDPTIL in the INVAL routine (in HCPALS). ..1. .... DSCSHDLK X'20' Demand Scan owns the Shadow Table Lock (VMDSHDLK) now. ...1 .... DSCDFRCT X'10' Demand Scan has incremented the Deferred Work count. .... 1... DSCSHFRM X'08' Stealing shared frames, which means we must ALWAYS use IPTE. .... .1.. DSCPTILS X'04' Note that VMDPTIL was obtained SHARED (verses EXCLUSIVE). 0002 2 Bitstring 1 DSCTERM Flags to tell the Steal Task how to handle RABIs, Unreferenced frames, and end-of-scan. 1... .... DSCRBINX X'80' Do NOT move RABIs to XSTORE .1.. .... DSCUNREF X'40' Take UNREFERENCED frames only ..1. .... DSCPURGE X'20' Perform a PTLB (Purge Translate Look-Aside Buffers). .... ...1 DSCAGAIN X'01' Steal should re-invoke itself at the end of the current cycle. .... .... DSCDONE X'00' Do NOT try to restart Demand Scan at the end of the current cycle. 0003 3 Bitstring 1 DSCXSTFL XSTORE management flags 1... .... DSCXSTOR X'80' Try paging out to XSTORE before sending them to DASD .... .... DSCNOXST X'00' Page out directly to DASD 0004 4 Signed 4 DSCINPUT (0) Demand Scan Input Word DSCINPUT is a word of "input status" hints for other parts of the system to communicate information "hints" to demand scan. NOTES : DSCINPUT fields are NOT serialized, by the demand scan lock or anything else. 0004 4 Bitstring 1 DSCINPB0 1... .... DSCSFCTG X'80' Single frame allocation has reached into the contiguous portion of the available list since the last time we checked. 0005 5 Bitstring 1 DSCINPB1 0006 6 Bitstring 1 DSCINPB2 0007 7 Bitstring 1 DSCINPB3 The primary Demand Scan may be able to satisfy the system requirement without performing every possible scan. In order to drain frames from every possible source, a "Round Robin" algorithm is used to select a different scan routine each time Demand Scan runs. The pointer DSCELEM holds the address of the next scan element (a structure defined in HCPALD). The next scan will be performed by the routine associated with this scan element. 0008 8 Signed 4 DSCCYCL Count the number of scan cycles 000C 12 Address 4 DSCELEM Address of next scan element (see HCPALD SCANELEM structure) These fields apply to the current Demand Scan. 0010 16 Signed 4 DSCTOTAL Total pages stolen by the current Demand Scan process 0014 20 Signed 4 * Reserved for IBM use 0018 24 Dbl-Word 8 DSCREQD (0) Frames needed by the system 0018 24 Signed 4 DSCREQD0 Frames needed from BELOW 2Gb 001C 28 Signed 4 DSCREQDG Frames needed from 2G and ABOVE 0020 32 Dbl-Word 8 DSCTRGT (0) Target frame limit (Low/High) 0020 32 Signed 4 DSCTRGT0 Target frames from BELOW 2Gb 0024 36 Signed 4 DSCTRGTG Target frames from 2Gb and ABOVE 0028 40 Dbl-Word 8 DSCFRMS (0) Frame counters (Low/High) 0028 40 Signed 4 DSCFRMS0 Frames stolen from BELOW 2Gb 002C 44 Signed 4 DSCFRMSG Frames stolen from 2Gb and ABOVE 0030 48 Dbl-Word 8 DSCSTLW (0) Steal Write counters (Low/High) 0030 48 Signed 4 DSCSTLW0 Steal Write frames BELOW 2Gb 0034 52 Signed 4 DSCSTLWG Steal Write frames 2Gb and ABOVE 0038 56 Address 4 DSCIOLFW I/O FRMTE list forward pointer 003C 60 Address 4 DSCIOLST I/O FRMTE list last FRMTE 0040 64 Address 4 DSCAVLLF Immediately available FRMTE list forward pointer 0044 68 Address 4 DSCPGMLF PGMBK FRMTE list forward pointer 0048 72 Signed 4 DSCPAGQC Count of FRMTEs on I/O and PGMBK FRMTE lists These fields are primarily for diagnostic purposes. They should not affect the operation of Demand Scan. 004C 76 Bitstring 1 DSCDEBUG Debug Flags 1... .... DSCACTIV X'80' Demand Scan is ACTIVE 004D 77 Bitstring 3 * reserved 0050 80 Signed 4 DSCCOUNT Count the number of times we entered Demand Scan (HCPALDSC) 0054 84 Bitstring 1 DSCALSCN Track our progress in HCPALSCN 0055 85 Bitstring 1 DSCALSCS Track our progress in HCPALSCS 0056 86 Bitstring 1 DSCALSCD Track our progress in HCPALSCD 0057 87 Bitstring 5 * Reserved 005C 92 Address 4 DSCWHOCM Last caller of CALCMORE routine 0060 96 Address 4 DSCWHOEX Previous HCPCALL before CALCMORE 0064 100 Bitstring 1 DSC$END (0) End of DSCBK 00000064 DSCBKLN *-DSCBK DSCBK length (in bytes) 0000000D DSCBKSZ (*-DSCBK+7)/8 DSCBK size (in doublewords)
DSCBK Storage Layout
*** DSCBK - Demand Scan Control Block
*
* +------+------+------+------+------+------+------+------+
* 0 |:PROG |:LKFLG|:TERM |:XSTFL|:INPB0|:INPB1|:INPB2|:INPB3|
* +------+------+------+------+------+------+------+------+
* 8 | DSCCYCL | DSCELEM |
* +---------------------------+---------------------------+
* 10 | DSCTOTAL |///////////////////////////|
* +---------------------------+---------------------------+
* 18 | DSCREQD0 | DSCREQDG |
* +---------------------------+---------------------------+
* 20 | DSCTRGT0 | DSCTRGTG |
* +---------------------------+---------------------------+
* 28 | DSCFRMS0 | DSCFRMSG |
* +---------------------------+---------------------------+
* 30 | DSCSTLW0 | DSCSTLWG |
* +---------------------------+---------------------------+
* 38 | DSCIOLFW | DSCIOLST |
* +---------------------------+---------------------------+
* 40 | DSCAVLLF | DSCPGMLF |
* +---------------------------+------+--------------------+
* 48 | DSCPAGQC |:DEBUG|////////////////////|
* +---------------------------+------+------+------+------+
* 50 | DSCCOUNT |:ALSCN|:ALSCS|:ALSCD|//////|
* +---------------------------+------+------+------+------+
* 58 |///////////////////////////| DSCWHOCM |
* +---------------------------+---------------------------+
* 60 | DSCWHOEX |
* +---------------------------+
*
*** DSCBK - Demand Scan Control Block
DSCBK Cross Reference
Symbol Dspl Value -------------- ---- ----- DSC$END 0064 DSCACTIV 004C 80 DSCAGAIN 0002 01 DSCALSCD 0056 DSCALSCN 0054 DSCALSCS 0055 DSCAVLLF 0040 DSCA2GPP 0000 01 DSCBKLN 0064 00000064 DSCBKSZ 0064 0000000D DSCCOUNT 0050 DSCCYCL 0008 DSCDEBUG 004C DSCDFRCT 0001 10 DSCDLSCN 0000 04 DSCDONE 0002 00 DSCELEM 000C DSCEMRGP 0000 20 DSCFRMS 0028 DSCFRMSG 002C DSCFRMS0 0028 DSCINPB0 0004 DSCINPB1 0005 DSCINPB2 0006 DSCINPB3 0007 DSCINPUT 0004 DSCIOLFW 0038 DSCIOLST 003C DSCLKFLG 0001 DSCLTD 0000 10 DSCLTDHX 0000 08 DSCNOXST 0003 00 DSCPAGQC 0048 DSCPASS1 0000 80 DSCPASS2 0000 40 DSCPGMLF 0044 DSCPROG 0000 DSCPTILK 0001 80 DSCPTILS 0001 04 DSCPTIL2 0001 40 DSCPURGE 0002 20 DSCRBINX 0002 80 DSCREQD 0018 DSCREQDG 001C DSCREQD0 0018 DSCSFCTG 0004 80 DSCSHDLK 0001 20 DSCSHFRM 0001 08 DSCSTLW 0030 DSCSTLWG 0034 DSCSTLW0 0030 DSCTERM 0002 DSCTKALL 0000 02 DSCTOTAL 0010 DSCTRGT 0020 DSCTRGTG 0024 DSCTRGT0 0020 DSCUNREF 0002 40 DSCWHOCM 005C DSCWHOEX 0060 DSCWORD 0000 DSCXSTFL 0003 DSCXSTOR 0003 80
Copyright IBM Corporation, 1990, 2004