On 08.09.2015 5:45, Zhang Zhen wrote:
The arch-specific IOREMAP_MAX_ORDER is introduced in
commit: ff0daca([ARM] Add section support to ioremap) and
commit: a069c89 ([ARM] 3705/1: add supersection support to ioremap()).
But supersections and sections mappings are only used in !SMP && !LPAE case.
Otherwise, mapping is created using the usual 4K pages.

In most cases without !SMP && !LPAE, the big alignment cause high fragmentation
issue in vmalloc area.
Here we use arch-specific IOREMAP_MAX_ORDER only in !SMP && !LPAE case,
otherwise use generic IOREMAP_MAX_ORDER in include/linux/vmalloc.h.

Signed-off-by: Zhang Zhen <zhenzhang.zh...@huawei.com>
---
  arch/arm/include/asm/memory.h | 2 ++
  1 file changed, 2 insertions(+)

diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
index b7f6fb4..3209012 100644
--- a/arch/arm/include/asm/memory.h
+++ b/arch/arm/include/asm/memory.h
@@ -76,10 +76,12 @@
   */
  #define XIP_VIRT_ADDR(physaddr)  (MODULES_VADDR + ((physaddr) & 0x000fffff))

+#if !defined(CONFIG_SMP) && !defined(CONFIG_ARM_LPAE)
  /*
   * Allow 16MB-aligned ioremap pages
   */
  #define IOREMAP_MAX_ORDER     24
+#endif

  #else /* CONFIG_MMU */


Hmm... This looks exactly like my old patch -
http://thread.gmane.org/gmane.linux.kernel.mm/127620
(Thanks to Vladimir for pointing that out!)

Hasn't there been any progress about this issue?
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