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Refactor the computation of the chunk size into its own function, thus avoiding an "unreachable code" error from clang.

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 Change: 184482
 ServerID: perforce.ravenbrook.com
This commit is contained in:
Gareth Rees 2014-02-24 21:32:22 +00:00
parent 09dd8e7027
commit c1ef37731a
1 changed files with 31 additions and 27 deletions
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58
mps/code/arenavm.c
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@ -1,7 +1,7 @@
/* arenavm.c: VIRTUAL MEMORY ARENA CLASS
*
* $Id$
* Copyright (c) 2001-2013 Ravenbrook Limited. See end of file for license.
* Copyright (c) 2001-2014 Ravenbrook Limited. See end of file for license.
*
*
* DESIGN
@ -909,6 +909,34 @@ static Bool pagesFindFreeWithSegPref(Index *baseReturn, VMChunk *chunkReturn,
}
/* vmArenaChunkSize -- choose chunk size for arena extension
*
* .vmchunk.overhead: This code still lacks a proper estimate of
* the overhead required by a vmChunk for chunkStruct, page tables
* etc. For now, estimate it as 10%. RHSK 2007-12-21
*/
static Size vmArenaChunkSize(VMArena vmArena, Size size)
{
Size fraction = 10; /* 10% -- see .vmchunk.overhead */
Size chunkSize;
Size chunkOverhead;
/* 1: use extendBy, if it is big enough for size + overhead */
chunkSize = vmArena->extendBy;
chunkOverhead = chunkSize / fraction;
if(chunkSize > size && (chunkSize - size) >= chunkOverhead)
return chunkSize;
/* 2: use size + overhead (unless it overflows SizeMAX) */
chunkOverhead = size / (fraction - 1);
if((SizeMAX - size) >= chunkOverhead)
return size + chunkOverhead;
/* 3: use SizeMAX */
return SizeMAX;
}
/* vmArenaExtend -- Extend the arena by making a new chunk
*
* The size arg specifies how much we wish to allocate after the extension.
@ -919,31 +947,7 @@ static Res vmArenaExtend(VMArena vmArena, Size size)
Size chunkSize;
Res res;
/* Choose chunk size. */
/* .vmchunk.overhead: This code still lacks a proper estimate of */
/* the overhead required by a vmChunk for chunkStruct, page tables */
/* etc. For now, estimate it as 10%. RHSK 2007-12-21 */
do {
Size fraction = 10; /* 10% -- see .vmchunk.overhead */
Size chunkOverhead;
/* 1: use extendBy, if it is big enough for size + overhead */
chunkSize = vmArena->extendBy;
chunkOverhead = chunkSize / fraction;
if(chunkSize > size && (chunkSize - size) >= chunkOverhead)
break;
/* 2: use size + overhead (unless it overflows SizeMAX) */
chunkOverhead = size / (fraction - 1);
if((SizeMAX - size) >= chunkOverhead) {
chunkSize = size + chunkOverhead;
break;
}
/* 3: use SizeMAX */
chunkSize = SizeMAX;
break;
} while(0);
chunkSize = vmArenaChunkSize(vmArena, size);
EVENT3(vmArenaExtendStart, size, chunkSize,
VMArenaReserved(VMArena2Arena(vmArena)));
@ -1571,7 +1575,7 @@ mps_arena_class_t mps_arena_class_vmnz(void)
/* C. COPYRIGHT AND LICENSE
*
* Copyright (C) 2001-2013 Ravenbrook Limited <http://www.ravenbrook.com/>.
* Copyright (C) 2001-2014 Ravenbrook Limited <http://www.ravenbrook.com/>.
* All rights reserved. This is an open source license. Contact
* Ravenbrook for commercial licensing options.
*