dd752c1ffd
Revert 245ae6036c (Support --with-lg-page
values larger than actual page size.), because it could cause VM map
fragmentation if the kernel grows mmap()ed memory downward.
This resolves #391.
77 lines
1.9 KiB
C
77 lines
1.9 KiB
C
#define JEMALLOC_EXTENT_MMAP_C_
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#include "jemalloc/internal/jemalloc_internal.h"
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/******************************************************************************/
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static void *
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extent_alloc_mmap_slow(size_t size, size_t alignment, bool *zero, bool *commit)
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{
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void *ret;
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size_t alloc_size;
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alloc_size = size + alignment - PAGE;
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/* Beware size_t wrap-around. */
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if (alloc_size < size)
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return (NULL);
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do {
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void *pages;
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size_t leadsize;
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pages = pages_map(NULL, alloc_size, commit);
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if (pages == NULL)
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return (NULL);
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leadsize = ALIGNMENT_CEILING((uintptr_t)pages, alignment) -
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(uintptr_t)pages;
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ret = pages_trim(pages, alloc_size, leadsize, size, commit);
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} while (ret == NULL);
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assert(ret != NULL);
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*zero = true;
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return (ret);
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}
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void *
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extent_alloc_mmap(void *new_addr, size_t size, size_t alignment, bool *zero,
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bool *commit)
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{
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void *ret;
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size_t offset;
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/*
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* Ideally, there would be a way to specify alignment to mmap() (like
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* NetBSD has), but in the absence of such a feature, we have to work
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* hard to efficiently create aligned mappings. The reliable, but
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* slow method is to create a mapping that is over-sized, then trim the
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* excess. However, that always results in one or two calls to
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* pages_unmap().
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*
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* Optimistically try mapping precisely the right amount before falling
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* back to the slow method, with the expectation that the optimistic
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* approach works most of the time.
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*/
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assert(alignment != 0);
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ret = pages_map(new_addr, size, commit);
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if (ret == NULL || ret == new_addr)
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return (ret);
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assert(new_addr == NULL);
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offset = ALIGNMENT_ADDR2OFFSET(ret, alignment);
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if (offset != 0) {
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pages_unmap(ret, size);
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return (extent_alloc_mmap_slow(size, alignment, zero, commit));
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}
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assert(ret != NULL);
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*zero = true;
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return (ret);
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}
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bool
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extent_dalloc_mmap(void *addr, size_t size)
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{
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if (config_munmap)
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pages_unmap(addr, size);
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return (!config_munmap);
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}
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