zeroshade commented on code in PR #289:
URL: https://github.com/apache/arrow-go/pull/289#discussion_r1966328267
##########
arrow/memory/mallocator/mallocator.go:
##########
@@ -58,28 +70,44 @@ func (alloc *Mallocator) Allocate(size int) []byte {
if size < 0 {
panic("mallocator: negative size")
}
- ptr, err := C.calloc(C.size_t(size), 1)
+ paddedSize := C.size_t(size) + C.size_t(alloc.alignment)
+ ptr, err := C.calloc(paddedSize, 1)
if err != nil {
// under some circumstances and allocation patterns, we can end
up in a scenario
// where for some reason calloc return ENOMEM even though there
is definitely memory
// available for use. So we attempt to fallback to simply doing
malloc + memset in
// this case. If malloc returns a nil pointer, then we know
we're out of memory
// and will surface the error.
- if ptr = C.malloc(C.size_t(size)); ptr == nil {
+ if ptr = C.malloc(paddedSize); ptr == nil {
panic(err)
}
- C.memset(ptr, 0, C.size_t(size))
+ C.memset(ptr, 0, C.size_t(paddedSize))
} else if ptr == nil {
panic("mallocator: out of memory")
}
+ buf := unsafe.Slice((*byte)(ptr), paddedSize)
+ aligned := roundToPowerOf2(uintptr(ptr), uintptr(alloc.alignment))
+ alloc.realAllocations.Store(aligned, uintptr(ptr))
atomic.AddUint64(&alloc.allocatedBytes, uint64(size))
- return unsafe.Slice((*byte)(ptr), size)
+
+ if uintptr(ptr) != aligned {
+ shift := aligned - uintptr(ptr)
+ return buf[shift : uintptr(size)+shift : uintptr(size)+shift]
Review Comment:
Ah weird. I always thought it was an absolute capacity for some reason...
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