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Adjust XML allocation pages to have the exact specified size

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Previously the page size was defining the data size, and due to additional
headers (+ recently removed allocation padding) the actual allocation was a bit
bigger.

The problem is that some allocators round 2^N+k allocations to 2^N+M, which can
result in noticeable waste of space. Specifically, on 64-bit OSX allocating the
previous page size (32k+40) resulted in 32k+512 allocation, thereby wasting 472
bytes, or 1.4%.

Now we have the allocation size specified exactly and just recompute the available
data size, which can in small space savings depending on the allocator.
This commit is contained in:
Arseny Kapoulkine 2016-04-14 08:43:06 -07:00
parent 2e0ed8284b
commit 2d5980b406
1 changed files with 8 additions and 8 deletions
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16
src/pugixml.cpp
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@ -403,14 +403,6 @@ PUGI__NS_END
#endif #endif
PUGI__NS_BEGIN PUGI__NS_BEGIN
static const size_t xml_memory_page_size =
#ifdef PUGIXML_MEMORY_PAGE_SIZE
PUGIXML_MEMORY_PAGE_SIZE
#else
32768
#endif
;
#ifdef PUGIXML_COMPACT #ifdef PUGIXML_COMPACT
static const uintptr_t xml_memory_block_alignment = 4; static const uintptr_t xml_memory_block_alignment = 4;
#else #else
@ -476,6 +468,14 @@ PUGI__NS_BEGIN
#endif #endif
}; };
static const size_t xml_memory_page_size =
#ifdef PUGIXML_MEMORY_PAGE_SIZE
(PUGIXML_MEMORY_PAGE_SIZE)
#else
32768
#endif
- sizeof(xml_memory_page);
struct xml_memory_string_header struct xml_memory_string_header
{ {
uint16_t page_offset; // offset from page->data uint16_t page_offset; // offset from page->data