__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.
+2016-04-23 H.J. Lu <hongjiu.lu@intel.com>
+
+ * elf/dl-minimal.c (__libc_memalign): Mmap one extra page.
+
2016-04-23 Mike Frysinger <vapier@gentoo.org>
* locale/programs/ld-time.c (time_finish): Set week_1stweek to 7
if (alloc_ptr + n >= alloc_end || n >= -(uintptr_t) alloc_ptr)
{
- /* Insufficient space left; allocate another page. */
+ /* Insufficient space left; allocate another page plus one extra
+ page to reduce number of mmap calls. */
caddr_t page;
size_t nup = (n + GLRO(dl_pagesize) - 1) & ~(GLRO(dl_pagesize) - 1);
- if (__glibc_unlikely (nup == 0))
- {
- if (n)
- return NULL;
- nup = GLRO(dl_pagesize);
- }
+ if (__glibc_unlikely (nup == 0 && n != 0))
+ return NULL;
+ nup += GLRO(dl_pagesize);
page = __mmap (0, nup, PROT_READ|PROT_WRITE,
MAP_ANON|MAP_PRIVATE, -1, 0);
if (page == MAP_FAILED)