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Date: Mon, 7 Jul 2008 14:49:11 +0200
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Akinobu Mita <akinobu.mita@...il.com>
Cc: linux-kernel@...r.kernel.org, Pavel Machek <pavel@...e.cz>,
linux-pm@...ts.linux-foundation.org
Subject: Re: [PATCH 2/2] swsusp: simplify memory bitmap
On Saturday, 5 of July 2008, Akinobu Mita wrote:
> This patch simplifies the memory bitmap manipulations.
>
> - remove the member size in struct bm_block
>
> It is not necessary for struct bm_block to have the number of bit chunks
> that can be calculated by using end_pfn and start_pfn.
>
> - use find_next_bit() for memory_bm_next_pfn
>
> No need to invent the bitmap library only for the memory bitmap.
Thanks for doing this change, it looks OK.
I haven't have the time to test it yet, but once it's been tested, I'll push
it to Andrew for merging. I'll fold patch 1/2 into this one.
Thanks,
Rafael
> Signed-off-by: Akinobu Mita <akinobu.mita@...il.com>
> Cc: Pavel Machek <pavel@...e.cz>
> Cc: Rafael J. Wysocki <rjw@...k.pl>
> Cc: linux-pm@...ts.linux-foundation.org
> ---
> kernel/power/snapshot.c | 84 ++++++++++--------------------------------------
> 1 file changed, 19 insertions(+), 65 deletions(-)
>
> Index: 2.6-git/kernel/power/snapshot.c
> ===================================================================
> --- 2.6-git.orig/kernel/power/snapshot.c
> +++ 2.6-git/kernel/power/snapshot.c
> @@ -205,8 +205,7 @@ static void chain_free(struct chain_allo
> * objects. The main list's elements are of type struct zone_bitmap
> * and each of them corresonds to one zone. For each zone bitmap
> * object there is a list of objects of type struct bm_block that
> - * represent each blocks of bit chunks in which information is
> - * stored.
> + * represent each blocks of bitmap in which information is stored.
> *
> * struct memory_bitmap contains a pointer to the main list of zone
> * bitmap objects, a struct bm_position used for browsing the bitmap,
> @@ -224,26 +223,27 @@ static void chain_free(struct chain_allo
> * pfns that correspond to the start and end of the represented zone.
> *
> * struct bm_block contains a pointer to the memory page in which
> - * information is stored (in the form of a block of bit chunks
> - * of type unsigned long each). It also contains the pfns that
> - * correspond to the start and end of the represented memory area and
> - * the number of bit chunks in the block.
> + * information is stored (in the form of a block of bitmap)
> + * It also contains the pfns that correspond to the start and end of
> + * the represented memory area.
> */
>
> #define BM_END_OF_MAP (~0UL)
>
> -#define BM_CHUNKS_PER_BLOCK (PAGE_SIZE / sizeof(long))
> -#define BM_BITS_PER_CHUNK (sizeof(long) << 3)
> #define BM_BITS_PER_BLOCK (PAGE_SIZE << 3)
>
> struct bm_block {
> struct bm_block *next; /* next element of the list */
> unsigned long start_pfn; /* pfn represented by the first bit */
> unsigned long end_pfn; /* pfn represented by the last bit plus 1 */
> - unsigned int size; /* number of bit chunks */
> - unsigned long *data; /* chunks of bits representing pages */
> + unsigned long *data; /* bitmap representing pages */
> };
>
> +static inline unsigned long bm_block_bits(struct bm_block *bb)
> +{
> + return bb->end_pfn - bb->start_pfn;
> +}
> +
> struct zone_bitmap {
> struct zone_bitmap *next; /* next element of the list */
> unsigned long start_pfn; /* minimal pfn in this zone */
> @@ -257,7 +257,6 @@ struct zone_bitmap {
> struct bm_position {
> struct zone_bitmap *zone_bm;
> struct bm_block *block;
> - int chunk;
> int bit;
> };
>
> @@ -272,12 +271,6 @@ struct memory_bitmap {
>
> /* Functions that operate on memory bitmaps */
>
> -static inline void memory_bm_reset_chunk(struct memory_bitmap *bm)
> -{
> - bm->cur.chunk = 0;
> - bm->cur.bit = -1;
> -}
> -
> static void memory_bm_position_reset(struct memory_bitmap *bm)
> {
> struct zone_bitmap *zone_bm;
> @@ -285,7 +278,7 @@ static void memory_bm_position_reset(str
> zone_bm = bm->zone_bm_list;
> bm->cur.zone_bm = zone_bm;
> bm->cur.block = zone_bm->bm_blocks;
> - memory_bm_reset_chunk(bm);
> + bm->cur.bit = 0;
> }
>
> static void memory_bm_free(struct memory_bitmap *bm, int clear_nosave_free);
> @@ -394,12 +387,10 @@ memory_bm_create(struct memory_bitmap *b
> bb->start_pfn = pfn;
> if (nr >= BM_BITS_PER_BLOCK) {
> pfn += BM_BITS_PER_BLOCK;
> - bb->size = BM_CHUNKS_PER_BLOCK;
> nr -= BM_BITS_PER_BLOCK;
> } else {
> /* This is executed only once in the loop */
> pfn += nr;
> - bb->size = DIV_ROUND_UP(nr, BM_BITS_PER_CHUNK);
> }
> bb->end_pfn = pfn;
> bb = bb->next;
> @@ -528,36 +519,6 @@ static int memory_bm_test_bit(struct mem
> return test_bit(bit, addr);
> }
>
> -/* Two auxiliary functions for memory_bm_next_pfn */
> -
> -/* Find the first set bit in the given chunk, if there is one */
> -
> -static inline int next_bit_in_chunk(int bit, unsigned long *chunk_p)
> -{
> - bit++;
> - while (bit < BM_BITS_PER_CHUNK) {
> - if (test_bit(bit, chunk_p))
> - return bit;
> -
> - bit++;
> - }
> - return -1;
> -}
> -
> -/* Find a chunk containing some bits set in given block of bits */
> -
> -static inline int next_chunk_in_block(int n, struct bm_block *bb)
> -{
> - n++;
> - while (n < bb->size) {
> - if (bb->data[n])
> - return n;
> -
> - n++;
> - }
> - return -1;
> -}
> -
> /**
> * memory_bm_next_pfn - find the pfn that corresponds to the next set bit
> * in the bitmap @bm. If the pfn cannot be found, BM_END_OF_MAP is
> @@ -571,40 +532,33 @@ static unsigned long memory_bm_next_pfn(
> {
> struct zone_bitmap *zone_bm;
> struct bm_block *bb;
> - int chunk;
> int bit;
>
> do {
> bb = bm->cur.block;
> do {
> - chunk = bm->cur.chunk;
> bit = bm->cur.bit;
> - do {
> - bit = next_bit_in_chunk(bit, bb->data + chunk);
> - if (bit >= 0)
> - goto Return_pfn;
> -
> - chunk = next_chunk_in_block(chunk, bb);
> - bit = -1;
> - } while (chunk >= 0);
> + bit = find_next_bit(bb->data, bm_block_bits(bb), bit);
> + if (bit < bm_block_bits(bb))
> + goto Return_pfn;
> +
> bb = bb->next;
> bm->cur.block = bb;
> - memory_bm_reset_chunk(bm);
> + bm->cur.bit = 0;
> } while (bb);
> zone_bm = bm->cur.zone_bm->next;
> if (zone_bm) {
> bm->cur.zone_bm = zone_bm;
> bm->cur.block = zone_bm->bm_blocks;
> - memory_bm_reset_chunk(bm);
> + bm->cur.bit = 0;
> }
> } while (zone_bm);
> memory_bm_position_reset(bm);
> return BM_END_OF_MAP;
>
> Return_pfn:
> - bm->cur.chunk = chunk;
> - bm->cur.bit = bit;
> - return bb->start_pfn + chunk * BM_BITS_PER_CHUNK + bit;
> + bm->cur.bit = bit + 1;
> + return bb->start_pfn + bit;
> }
>
> /**
>
>
--
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