YggFileSeqmentImpl.mesa
Copyright Ó 1988 by Xerox Corporation. All rights reserved.
Bob Hagmann June 30, 1988 8:43:31 am PDT
Access to per-segment data structures
The first version of this code was created by editing LogicalVolumeImpl.
DIRECTORY
Basics USING [ BITAND, BITRSHIFT, BITXOR ],
Rope USING [ ROPE ],
YggDIDMap USING [ NullRun, Run ],
YggFile USING [ Error, PageCount, PageNumber ],
YggFileInternal USING [AllocWord, PTAllocBitmap, SegmentMetadata];
YggFileSeqmentImpl: CEDAR MONITOR LOCKS segment.first USING segment: LIST OF YggFileInternal.SegmentMetadata
IMPORTS Basics, YggFile
EXPORTS YggFileInternal
= {
Data types and variables
ROPE: TYPE ~ Rope.ROPE;
bitIn32BitWord: TYPE = INT [0..32);
debugging: BOOL ← TRUE;
Exported procedures for allocation
IsUsed: PUBLIC ENTRY PROC [segment: LIST OF YggFileInternal.SegmentMetadata, page: YggFile.PageNumber] RETURNS [inUse: BOOL ← FALSE] ~ {
Test to see if a page is in-use. This test is done under the monitor, but no guarantee is made about how long the result will be true. This flavor of test is for the shadow bitmap.
high: INT;
low5bits: bitIn32BitWord;
alloc: YggFileInternal.AllocWord;
[high, low5bits] ← decomposePageNo[page];
TRUSTED {alloc ← segment.first.vmAddressForShadowAllocMap[high];};
RETURN [alloc.bits[low5bits] ];
};
SetPageUsed: PUBLIC ENTRY PROC [segment: LIST OF YggFileInternal.SegmentMetadata, page: YggFile.PageNumber, inUse: BOOL] RETURNS [wasInUse: BOOL ← FALSE] ~ {
Test to see if a page is in-use, and set it to "inUse". This test is done under the monitor, but no guarantee is made about how long the result will be true. This flavor of operation is for the shadow bitmap.
high: INT;
low5bits: bitIn32BitWord;
alloc: YggFileInternal.AllocWord;
[high, low5bits] ← decomposePageNo[page];
TRUSTED {alloc ← segment.first.vmAddressForShadowAllocMap[high];};
IF alloc.bits[low5bits] THEN RETURN[TRUE]
ELSE {
alloc.bits[low5bits] ← TRUE;
RETURN[FALSE];
};
};
Alloc: PUBLIC ENTRY PROC [segment: LIST OF YggFileInternal.SegmentMetadata,
first: YggFile.PageNumber,
size, min: YggFile.PageCount,
minPage, maxPage: YggFile.PageNumber]
RETURNS [given: YggDIDMap.Run] ~ {
Find a logical run marked free in the in-memory bitmap. May be smaller than "size", but is never smaller than "min" if anything is allocated. If given.pages is 0 then no pages allocated. This flavor of allocation is for the shadow bitmap. To make the allocation stable, StableAlloc must be called with the run.
ENABLE UNWIND => NULL;
Restrict run length to LAST[CARDINAL], to maximize runs per run-table page
pos: YggFile.PageNumber;
realMaxPage: YggFile.PageNumber;
IF segment.first.freePages < size THEN RETURN WITH ERROR YggFile.Error[volumeFull];
IF size = 0 THEN RETURN[YggDIDMap.NullRun];
realMaxPage ← [MIN[segment.first.numberOfPages, maxPage]];
pos ← IF first = 0 THEN segment.first.rover ELSE first;
IF pos < minPage OR pos > maxPage THEN pos ← minPage;
min ← MAX[ MIN[min, size], 1 ]; -- otherwise the algorithm doesn't work!
Loop probing for a free page at "min" intervals
THROUGH [0 .. (realMaxPage-minPage+min-1)/min] DO
IF pos >= realMaxPage THEN pos ← [minPage];
IF NOT IsUsedInternal[segment, pos] THEN {
Expand around "pos" to see if there's a run of size at least "min"
start, end: YggFile.PageNumber ← pos;
given.pages ← 1;
WHILE start > 0 AND given.pages < size DO
IF IsUsedInternal[segment, [start-1]] THEN EXIT;
start ← [start-1];
given.pages ← given.pages + 1;
ENDLOOP;
WHILE end < segment.first.numberOfPages-1 AND given.pages < size DO
IF IsUsedInternal[segment, [end+1]] THEN EXIT;
end ← [end+1];
given.pages ← given.pages + 1;
ENDLOOP;
IF given.pages >= min THEN { given.firstPage ← start; EXIT };
};
pos ← [pos+min];
REPEAT FINISHED => RETURN[YggDIDMap.NullRun];
ENDLOOP;
doFreeOrAllocate[segment.first.vmAddressForShadowAllocMap, [segmentId: segment.first.segmentId, segmentPage: given.firstPage, firstPage: 0, pages: given.pages, leader: FALSE], TRUE];
IF first = 0 THEN segment.first.rover ← [given.firstPage];
};
StableAlloc: PUBLIC ENTRY PROC [segment: LIST OF YggFileInternal.SegmentMetadata, run: YggDIDMap.Run] ~ {
Set the disk resident bitmap for this run. The tid is a top level transaction that is trying to commit.
Add the dance for Camelot to pin and log the page(s) of the bitmap
doFreeOrAllocate[segment.first.vmAddressForSegmentAllocMap, run, TRUE];
};
Free: PUBLIC ENTRY PROC [segment: LIST OF YggFileInternal.SegmentMetadata, run: YggDIDMap.Run] ~ {
Mark the logical run free in the in-memory (shadow) bitmap.
doFreeOrAllocate[segment.first.vmAddressForShadowAllocMap, run, FALSE];
};
StableFree: PUBLIC ENTRY PROC [segment: LIST OF YggFileInternal.SegmentMetadata, run: YggDIDMap.Run] ~ {
Mark the logical run free in the stable bitmap.
Add the dance for Camelot to pin and log the page(s) of the bitmap
doFreeOrAllocate[segment.first.vmAddressForSegmentAllocMap, run, FALSE];
};
Internal procedures
IsUsedInternal: INTERNAL PROC [segment: LIST OF YggFileInternal.SegmentMetadata, page: YggFile.PageNumber] RETURNS [inUse: BOOL ← FALSE] ~ {
Test to see if a page is in-use. This test is done under the monitor, but no guarantee is made about how long the result will be true. This flavor of test is for the shadow bitmap.
high: INT;
low5bits: bitIn32BitWord;
alloc: YggFileInternal.AllocWord;
[high, low5bits] ← decomposePageNo[page];
TRUSTED {alloc ← segment.first.vmAddressForShadowAllocMap[high];};
RETURN [alloc.bits[low5bits] ];
};
decomposePageNo: PROC [page: YggFile.PageNumber] RETURNS [high: INT, low5bits: bitIn32BitWord] ~ {
low5bits ← Basics.BITAND[page, 01Fh];
high ← Basics.BITRSHIFT[page, 5];
};
doFreeOrAllocate: INTERNAL PROC [vmAddressForWhateverBitmap: YggFileInternal.PTAllocBitmap, run: YggDIDMap.Run, allocation: BOOL] ~ {
Mark the logical run free in the in-memory (shadow) bitmap.
currentPage: CARD ← run.segmentPage;
pagesLeft: CARD ← run.pages;
high: INT;
low5bits: bitIn32BitWord;
bitsToDo: bitIn32BitWord;
alloc: YggFileInternal.AllocWord;
Do individual bits on non-entire word
[high, low5bits] ← decomposePageNo[[currentPage]];
bitsToDo ← MIN[32-low5bits, pagesLeft];
IF bitsToDo > 0 THEN {
TRUSTED {alloc ← vmAddressForWhateverBitmap[high];};
FOR bitNo: bitIn32BitWord IN [low5bits..low5bits+bitsToDo) DO
IF debugging AND alloc.bits[bitNo] = allocation THEN ERROR;
alloc.bits[bitNo] ← allocation;
ENDLOOP;
TRUSTED {vmAddressForWhateverBitmap[high] ← alloc};
currentPage ← currentPage + bitsToDo;
pagesLeft ← pagesLeft - bitsToDo;
};
IF pagesLeft # 0 THEN {
pagesToDo: CARD;
pagesToDo ← decomposePageNo[[pagesLeft]].high;
[high, low5bits] ← decomposePageNo[[currentPage]];
IF pagesToDo > 0 THEN {
allOnesOrAllZeros: YggFileInternal.AllocWord ← IF allocation THEN LOOPHOLE[0] ELSE LOOPHOLE[0FFFFFFFFh];
FOR c: CARD IN [high..high+pagesToDo) DO
TRUSTED {IF debugging AND Basics.BITXOR[LOOPHOLE[allOnesOrAllZeros], LOOPHOLE[vmAddressForWhateverBitmap[c]]] # 0 THEN ERROR; };
TRUSTED {vmAddressForWhateverBitmap[c] ← allOnesOrAllZeros;};
currentPage ← currentPage + 32;
pagesLeft ← pagesLeft - 32;
ENDLOOP;
};
[high, low5bits] ← decomposePageNo[[currentPage]];
bitsToDo ← MIN[32-low5bits, pagesLeft];
IF bitsToDo > 0 THEN {
TRUSTED {alloc ← vmAddressForWhateverBitmap[high];};
FOR bitNo: bitIn32BitWord IN [low5bits..low5bits+bitsToDo) DO
IF debugging AND alloc.bits[bitNo] = allocation THEN ERROR;
alloc.bits[bitNo] ← allocation;
ENDLOOP;
TRUSTED {vmAddressForWhateverBitmap[high] ← alloc};
currentPage ← currentPage + bitsToDo;
pagesLeft ← pagesLeft - bitsToDo;
};
};
};
******** Volume Allocation Map ********
 --FileInternal.--
Alloc: PUBLIC ENTRY PROC [volume: Volume, first: VolumeFormat.LogicalPage, size, min: VolumeFormat.LogicalPageCount, minPage, maxPage: VolumeFormat.LogicalPage, largeFile: BOOL] RETURNS [given: VolumeFormat.LogicalRun] = TRUSTED {
ENABLE UNWIND => NULL;
Restrict run length to LAST[CARDINAL], to maximize runs per run-table page
reqSize: VolumeFormat.RunPageCount = MIN[size,LAST[VolumeFormat.RunPageCount]];
pos: VolumeFormat.LogicalPage;
vam: VAM;
realMaxPage: VolumeFormat.LogicalPage;
WHILE volume.checkpointing DO WAIT notCheckpointing ENDLOOP;
IF volume.vamStatus # ok THEN RETURN WITH ERROR File.Error[volume.vamStatus];
IF volume.free < size THEN RETURN WITH ERROR File.Error[volumeFull];
IF size = 0 THEN RETURN[[first: first, size: 0]]; -- main algorithm gives at least one page
vam ← volume.vam;
realMaxPage ← [MIN[vam.size, maxPage]];
pos ← IF first = 0 THEN vam.rover ELSE first;
IF pos < minPage OR pos > maxPage THEN pos ← minPage;
min ← MAX[ MIN[min, reqSize], 1 ]; -- otherwise the algorithm doesn't work!
Loop probing for a free page at "min" intervals
THROUGH [0 .. (realMaxPage-minPage+min-1)/min] DO
IF pos >= realMaxPage THEN pos ← [minPage];
IF NOT Used[vam, pos] THEN {
Expand around "pos" to see if there's a run of size at least "min"
start, end: VolumeFormat.LogicalPage ← pos;
given.size ← 1;
WHILE start > 0 AND given.size < reqSize
DO IF Used[vam, [start-1]] THEN EXIT;
start ← [start-1]; given.size ← given.size + 1;
ENDLOOP;
WHILE end < vam.size-1 AND given.size < reqSize
DO IF Used[vam, [end+1]] THEN EXIT;
end ← [end+1]; given.size ← given.size + 1;
ENDLOOP;
IF given.size >= min THEN { given.first ← start; EXIT };
};
pos ← [pos+min];
REPEAT FINISHED => RETURN WITH ERROR File.Error[volumeFull]
ENDLOOP;
volume.vamChanged ← TRUE;
FOR i: INT IN [0..given.size) DO
[] ← SetUsed[volume, [given.first+i], TRUE];
ENDLOOP;
IF volume.labeled THEN {
IF first = 0 THEN vam.rover ← given.first;
}
ELSE {
IF largeFile THEN volume.largeVAMrover ← given.first ELSE volume.smallVAMrover ← given.first;
IF volume.volatileVAM AND volume.vamStable THEN { -- vam is no longer stable
why: File.RC;
volume.vamStable ← FALSE;
volume.root.vamStable ← FALSE;
why ← RootTransfer[volume: volume, direction: write];
IF why # ok THEN RETURN WITH ERROR File.Error[why];
};
};
ConsiderFlushing[volume];
};
}.