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Add option to disable munmap() use in the allocator.

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When compiling with '-d:nimAllocNoUnmap', the allocator will not
attempt to return large chunks to the OS. For certain allocation
behaviors, this can be a significant speedup.
This commit is contained in:
Reimer Behrends 2015-09-18 14:05:04 +02:00
commit 9ea99dbf36
1 changed files with 7 additions and 4 deletions
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11
lib/system/alloc.nim
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@ -27,8 +27,11 @@ sysAssert(roundup(65, 8) == 72, "roundup broken 2")
# some platforms have really weird unmap behaviour: unmap(blockStart, PageSize) # some platforms have really weird unmap behaviour: unmap(blockStart, PageSize)
# really frees the whole block. Happens for Linux/PowerPC for example. Amd64 # really frees the whole block. Happens for Linux/PowerPC for example. Amd64
# and x86 are safe though; Windows is special because MEM_RELEASE can only be # and x86 are safe though; Windows is special because MEM_RELEASE can only be
# used with a size of 0: # used with a size of 0. We also allow unmapping to be turned off with
const weirdUnmap = not (defined(amd64) or defined(i386)) or defined(windows) # -d:nimAllocNoUnmap:
const doNotUnmap = not (defined(amd64) or defined(i386)) or
defined(windows) or defined(nimAllocNoUnmap)
when defined(posix): when defined(posix):
const const
@ -478,7 +481,7 @@ proc freeBigChunk(a: var MemRegion, c: PBigChunk) =
excl(a.chunkStarts, pageIndex(c)) excl(a.chunkStarts, pageIndex(c))
c = cast[PBigChunk](le) c = cast[PBigChunk](le)
if c.size < ChunkOsReturn or weirdUnmap: if c.size < ChunkOsReturn or doNotUnmap:
incl(a, a.chunkStarts, pageIndex(c)) incl(a, a.chunkStarts, pageIndex(c))
updatePrevSize(a, c, c.size) updatePrevSize(a, c, c.size)
listAdd(a.freeChunksList, c) listAdd(a.freeChunksList, c)
@ -762,7 +765,7 @@ proc deallocOsPages(a: var MemRegion) =
# we free every 'ordinarily' allocated page by iterating over the page bits: # we free every 'ordinarily' allocated page by iterating over the page bits:
for p in elements(a.chunkStarts): for p in elements(a.chunkStarts):
var page = cast[PChunk](p shl PageShift) var page = cast[PChunk](p shl PageShift)
when not weirdUnmap: when not doNotUnmap:
var size = if page.size < PageSize: PageSize else: page.size var size = if page.size < PageSize: PageSize else: page.size
osDeallocPages(page, size) osDeallocPages(page, size)
else: else: