2012/10/29 Minchan Kim [off-list ref]:

On Mon, Oct 29, 2012 at 04:12:55AM +0900, Joonsoo Kim wrote:

quoted

In current code, after flush_all_zero_pkmaps() is invoked,
then re-iterate all pkmaps. It can be optimized if flush_all_zero_pkmaps()
return index of flushed entry. With this index,
we can immediately map highmem page to virtual address represented by index.
So change return type of flush_all_zero_pkmaps()
and return index of last flushed entry.

Signed-off-by: Joonsoo Kim <redacted>

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index ef788b5..0683869 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h

@@ -32,6 +32,7 @@ static inline void invalidate_kernel_vmap_range(void *vaddr, int size)

 #ifdef CONFIG_HIGHMEM
 #include <asm/highmem.h>
+#define PKMAP_INDEX_INVAL (-1)

How about this?

#define PKMAP_INVALID_INDEX (-1)

Okay.

quoted

 /* declarations for linux/mm/highmem.c */
 unsigned int nr_free_highpages(void);

diff --git a/mm/highmem.c b/mm/highmem.c
index 731cf9a..65beb9a 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c

@@ -106,10 +106,10 @@ struct page *kmap_to_page(void *vaddr)
      return virt_to_page(addr);
 }

-static void flush_all_zero_pkmaps(void)
+static int flush_all_zero_pkmaps(void)
 {
      int i;
-     int need_flush = 0;
+     int index = PKMAP_INDEX_INVAL;

      flush_cache_kmaps();

@@ -141,10 +141,12 @@ static void flush_all_zero_pkmaps(void)
                        &pkmap_page_table[i]);

              set_page_address(page, NULL);
-             need_flush = 1;
+             index = i;

How about returning first free index instead of last one?
and update last_pkmap_nr to it.

Okay. It will be more good.

Thanks.

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