counting bounce buffer in vmstat

Hi,

This is a updated version of a patch for counting bouce buffer page. A major change is :
/proc/vmstat is used to show usage.

Thanks
-- Kame

This is a patch for counting the number of pages for bounce buffer. It's shown in /proc/vmstat.

Currently, the number of bounce pages are not counted anywhere. So, if there are many bounce pages, it seems that there are leaked pages. And it's difficult for a user to imagine the usage of bounce pages. So, it's meaningful to show # of bouce pages.

---

 linux-2.6.12-rc2-mm3-kamezawa/include/linux/page-flags.h |    1 +
 linux-2.6.12-rc2-mm3-kamezawa/mm/highmem.c               |    2 ++
 linux-2.6.12-rc2-mm3-kamezawa/mm/page_alloc.c            |    1 +
 3 files changed, 4 insertions(+)

diff -puN mm/highmem.c~count_bounce mm/highmem.c
@@ -325,6 +325,7 @@ static void bounce_end_io(struct bio *bi
 			continue;
 
 		mempool_free(bvec->bv_page, pool);	
+		dec_page_state(nr_bounce);
 	}
 
 	bio_endio(bio_orig, bio_orig->bi_size, err);

@@ -405,6 +406,7 @@ static void __blk_queue_bounce(request_q
 		to->bv_page = mempool_alloc(pool, q->bounce_gfp);
 		to->bv_len = from->bv_len;
 		to->bv_offset = from->bv_offset;
+		inc_page_state(nr_bounce);
 
 		if (rw == WRITE) {
 			char *vto, *vfrom;

diff -puN mm/page_alloc.c~count_bounce mm/page_alloc.c
@@ -1902,6 +1902,7 @@ static char *vmstat_text[] = {
 	"nr_page_table_pages",
 	"nr_mapped",
 	"nr_slab",
+	"nr_bounce",
 
 	"pgpgin",
 	"pgpgout",

diff -puN include/linux/page-flags.h~count_bounce include/linux/page-flags.h
@@ -89,6 +89,7 @@ struct page_state {
 	unsigned long nr_page_table_pages;/* Pages used for pagetables */
 	unsigned long nr_mapped;	/* mapped into pagetables */
 	unsigned long nr_slab;		/* In slab */
+	unsigned long nr_bounce;	/* pages for bounce buffers */
 #define GET_PAGE_STATE_LAST nr_slab
 
 	/*

_

That's not really right.

There are two functions: get_page_state() and get_full_page_state(). get_page_state() only gets those fields up to and including GET_PAGE_STATE_LAST. The way you have the code laid out there implies that get_page_state() also calculates the total nr_bounce, only it doesn't.

I'll fix it up.

In article <[email protected]> (at Wed, 27 Apr 2005 15:42:13 +0900), KAMEZAWA Hiroyuki <[email protected]> says:

Oh, I misunderstood that.

Thank you.

-- Kame