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Reduce number of mmap calls from __libc_memalign in ld.so
__libc_memalign in ld.so allocates one page at a time and tries to optimize consecutive __libc_memalign calls by hoping that the next mmap is after the current memory allocation. However, the kernel hands out mmap addresses in top-down order, so this optimization in practice never happens, with the result that we have more mmap calls and waste a bunch of space for each __libc_memalign. This change makes __libc_memalign to mmap one page extra. Worst case, the kernel never puts a backing page behind it, but best case it allows __libc_memalign to operate much much better. For elf/tst-align --direct, it reduces number of mmap calls from 12 to 9. * elf/dl-minimal.c (__libc_memalign): Mmap one extra page.
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@ -1,3 +1,7 @@
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2016-04-23 H.J. Lu <hongjiu.lu@intel.com>
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* elf/dl-minimal.c (__libc_memalign): Mmap one extra page.
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2016-04-23 Mike Frysinger <vapier@gentoo.org>
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2016-04-23 Mike Frysinger <vapier@gentoo.org>
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* locale/programs/ld-time.c (time_finish): Set week_1stweek to 7
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* locale/programs/ld-time.c (time_finish): Set week_1stweek to 7
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@ -66,15 +66,13 @@ __libc_memalign (size_t align, size_t n)
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if (alloc_ptr + n >= alloc_end || n >= -(uintptr_t) alloc_ptr)
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if (alloc_ptr + n >= alloc_end || n >= -(uintptr_t) alloc_ptr)
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{
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{
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/* Insufficient space left; allocate another page. */
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/* Insufficient space left; allocate another page plus one extra
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page to reduce number of mmap calls. */
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caddr_t page;
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caddr_t page;
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size_t nup = (n + GLRO(dl_pagesize) - 1) & ~(GLRO(dl_pagesize) - 1);
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size_t nup = (n + GLRO(dl_pagesize) - 1) & ~(GLRO(dl_pagesize) - 1);
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if (__glibc_unlikely (nup == 0))
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if (__glibc_unlikely (nup == 0 && n != 0))
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{
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if (n)
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return NULL;
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return NULL;
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nup = GLRO(dl_pagesize);
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nup += GLRO(dl_pagesize);
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}
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page = __mmap (0, nup, PROT_READ|PROT_WRITE,
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page = __mmap (0, nup, PROT_READ|PROT_WRITE,
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MAP_ANON|MAP_PRIVATE, -1, 0);
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MAP_ANON|MAP_PRIVATE, -1, 0);
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if (page == MAP_FAILED)
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if (page == MAP_FAILED)
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