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mps br/vmarenagrow: arenavm.c: vmarenaextend() will:

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a) choose a better chunkSize;
   b) fallback to smaller sizes if request fails.
 *** WARNING ***
 VMChunkCreate() has test-code that deliberately fails requests,
 for testing this functionality.

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 Change: 163665
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This commit is contained in:
Richard Kistruck 2007-12-20 18:00:50 +00:00
parent 129da55b05
commit 9ac760252a
1 changed files with 54 additions and 7 deletions
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61
mps/code/arenavm.c
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@ -303,10 +303,19 @@ static Res VMChunkCreate(Chunk *chunkReturn, VMArena vmArena, Size size)
BootBlock boot = &bootStruct;
VMChunk vmChunk;
void *p;
static int counter = 0;
AVER(chunkReturn != NULL);
AVERT(VMArena, vmArena);
AVER(size > 0);
counter += 1;
if((counter % 4 == 2) || (counter % 4 == 3)) {
DIAG_SINGLEF(( "VMChunkCreate",
"DELIBERATELY FAILING REQUEST OF SIZE $W.\n", size,
NULL ));
return ResRESOURCE;
}
res = VMCreate(&vm, size);
if (res != ResOK)
@ -1051,24 +1060,62 @@ static Res vmArenaExtend(VMArena vmArena, Size size)
{
Chunk newChunk;
Size chunkSize;
Size chunkOverhead; /* for housekeeping tables etc */
Res res;
#if 0
/* .improve.debug: @@@@ chunkSize (calculated below) won't */
/* be big enough if the tables of the new chunk are */
/* more than vmArena->extendBy (because there will be fewer than */
/* size bytes free in the new chunk). Fix this. */
chunkSize = vmArena->extendBy + size;
#if 0
/* diagnostic: report when VM arena is extended */
DIAG_WRITEF(( DIAG_STREAM, "\n** vmArenaExtend $U\n", chunkSize,
NULL ));
DIAG( ArenaDescribe(VMArena2Arena(vmArena), DIAG_STREAM); );
#endif
chunkSize = vmArena->extendBy;
/* crude conservative estimate of chunkOverhead: 25% */
chunkOverhead = chunkSize / 4;
/* will chunkSize accommodate size + overhead? */
if(chunkSize > size && (chunkSize - size) >= chunkOverhead) {
/* yes: chunkSize is enough */
} else {
/* no: chunkSize is too small for this size, so: */
/* 1. make it size + chunkOverhead if we can; */
/* 2. or SizeMAX (which will fail, but nicely). */
Size headroom;
/* headroom: if size is enormous, how much before overflow? */
headroom = SizeMAX - size;
if(chunkOverhead < headroom) {
chunkSize = size + chunkOverhead;
} else {
chunkSize = SizeMAX;
}
}
res = VMChunkCreate(&newChunk, vmArena, chunkSize);
/* .improve.chunk-create.fail: If we fail we could try again */
/* (with a smaller size, say). We don't do this. */
/* RHSK 2007-12-19: We do now, in a brain-dead fashion, without */
/* checking why VMChunkCreate failed, or a minimum request size. */
DIAG_SINGLEF(( "vmArenaExtend_Start",
"VMArenaReserved currently $W bytes\n",
VMArenaReserved(VMArena2Arena(vmArena)),
NULL ));
for(;; chunkSize /= 2) {
res = VMChunkCreate(&newChunk, vmArena, chunkSize);
if(res == ResOK) {
break;
}
DIAG_SINGLEF(( "vmArenaExtend_Attempt",
"Tried to reserve new chunk of VM $W bytes;", chunkSize,
" result $U\n", res,
NULL ));
}
DIAG_SINGLEF(( "vmArenaExtend_Done",
"Reserved new chunk of VM $W bytes.\n", chunkSize,
"VMArenaReserved now...... $W bytes\n",
VMArenaReserved(VMArena2Arena(vmArena)),
NULL ));
return res;
}