riscv: Adjust mmap base address at a third of task size

aghiti · palmer-dabbelt · commit ae662eec8a51 · 2019-01-25T10:50:53.000-08:00
This ratio is the most used among all other architectures and make
icache_hygiene libhugetlbfs test pass: this test mmap lots of
hugepages whose addresses, without this patch, reach the end of
the process user address space.

Signed-off-by: Alexandre Ghiti &lt;aghiti@upmem.com&gt;
Reviewed-by: Christoph Hellwig &lt;hch@lst.de&gt;
Signed-off-by: Palmer Dabbelt &lt;palmer@sifive.com&gt;
diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
@@ -22,7 +22,7 @@
  * This decides where the kernel will search for a free chunk of vm
  * space during mmap's.
  */
-#define TASK_UNMAPPED_BASE	PAGE_ALIGN(TASK_SIZE >> 1)
+#define TASK_UNMAPPED_BASE	PAGE_ALIGN(TASK_SIZE / 3)
 
 #define STACK_TOP		TASK_SIZE
 #define STACK_TOP_MAX		STACK_TOP
