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Added more control over write barrier. in particular separated scans after a hit.

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 Change: 186988
 ServerID: perforce.ravenbrook.com
This commit is contained in:
David Lovemore 2014-08-27 11:21:18 +01:00
parent 46d723c9dc
commit b4460043e6
4 changed files with 21 additions and 13 deletions
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14
mps/code/config.h
View file

@ -637,10 +637,18 @@
/* Experimental Scan Barrier threshold
*
* The number of unecessary scans performed, before raising the write
* barrier to remember the refset summary.
*/
#define TRACE_SCAN_BARRIER_THRESHOLD 3
/* Number of bits needed to keep the seg scan count */
#define SEG_SCANS_BITS 10
/* The number of unecessary scans performed, before raising the write
* barrier to remember the refset summary. */
#define SEG_SCANS_INIT 3
/* The number of unecessary scans performed, before raising the write
* barrier to remember the refset summary, after a necessary scan */
#define SEG_SCANS_AFTER_NEEDED_SCAN 3
/* The number of unecessary scans performed, before raising the write
* barrier to remember the refset summary, after a barrier hit */
#define SEG_SCANS_AFTER_HIT 1
#endif /* config_h */

2
mps/code/mpmst.h
View file

@ -285,6 +285,7 @@ typedef struct SegStruct { /* segment structure */
TraceSet white : TraceLIMIT; /* traces for which seg is white */
TraceSet nailed : TraceLIMIT; /* traces for which seg has nailed objects */
RankSet rankSet : RankLIMIT; /* ranks of references in this seg */
unsigned scans : SEG_SCANS_BITS; /* use write barrier after this many scans */
} SegStruct;
@ -300,7 +301,6 @@ typedef struct GCSegStruct { /* GC segment structure */
RingStruct greyRing; /* link in list of grey segs */
RefSet summary; /* summary of references out of seg */
Buffer buffer; /* non-NULL if seg is buffered */
unsigned unnecessaryScans; /* consecutive unnecessary scans performed */
Sig sig; /* <design/sig/> */
} GCSegStruct;

2
mps/code/seg.c
View file

@ -160,6 +160,7 @@ static Res SegInit(Seg seg, Pool pool, Addr base, Size size,
seg->grey = TraceSetEMPTY;
seg->pm = AccessSetEMPTY;
seg->sm = AccessSetEMPTY;
seg->scans = SEG_SCANS_INIT;
seg->depth = 0;
seg->firstTract = NULL;
@ -1082,7 +1083,6 @@ static Res gcSegInit(Seg seg, Pool pool, Addr base, Size size,
gcseg->summary = RefSetEMPTY;
gcseg->buffer = NULL;
gcseg->unnecessaryScans = 0;
RingInit(&gcseg->greyRing);
gcseg->sig = GCSegSig;

16
mps/code/trace.c
View file

@ -1105,7 +1105,6 @@ static Res traceScanSegRes(TraceSet ts, Rank rank, Arena arena, Seg seg)
} else { /* scan it */
ScanStateStruct ssStruct;
ScanState ss = &ssStruct;
Bool considerBarrier = FALSE;
ScanStateInit(ss, ts, arena, rank, white);
/* Expose the segment to make sure we can scan it. */
@ -1138,16 +1137,14 @@ static Res traceScanSegRes(TraceSet ts, Rank rank, Arena arena, Seg seg)
AVER(RefSetSub(ScanStateUnfixedSummary(ss), SegSummary(seg)));
if (ZoneSetInter(ScanStateUnfixedSummary(ss), white) == ZoneSetEMPTY) {
/* a scan was not necessary */
if (((GCSeg)seg)->unnecessaryScans < TRACE_SCAN_BARRIER_THRESHOLD) {
((GCSeg)seg)->unnecessaryScans++;
} else {
considerBarrier = TRUE;
}
if (seg->scans > 0)
seg->scans--;
} else {
((GCSeg)seg)->unnecessaryScans = 0;
if (seg->scans < SEG_SCANS_AFTER_NEEDED_SCAN)
seg->scans = SEG_SCANS_AFTER_NEEDED_SCAN;
}
if (considerBarrier) {
if (seg->scans == 0) {
if(res != ResOK || !wasTotal) {
/* scan was partial, so... */
/* scanned summary should be ORed into segment summary. */
@ -1217,6 +1214,9 @@ void TraceSegAccess(Arena arena, Seg seg, AccessSet mode)
EVENT3(TraceAccess, arena, seg, mode);
if ((mode & SegSM(seg) & AccessWRITE) != 0) /* write barrier? */
seg->scans = SEG_SCANS_AFTER_HIT;
if((mode & SegSM(seg) & AccessREAD) != 0) { /* read barrier? */
Trace trace;
TraceId ti;