On Tuesday, September 30, 2014 01:31:29 PM Joerg Roedel wrote:
> From: Joerg Roedel <[email protected]>
>
> The existing implementation of swsusp_free iterates over all
> pfns in the system and checks every bit in the two memory
> bitmaps.
>
> This doesn't scale very well with large numbers of pfns,
> especially when the bitmaps are not populated very densly.
> Change the algorithm to iterate over the set bits in the
> bitmaps instead to make it scale better in large memory
> configurations.
>
> Also add a memory_bm_clear_current() helper function that
> clears the bit for the last position returned from the
> memory bitmap.
>
> This new version adds a !NULL check for the memory bitmaps
> before they are walked. Not doing so causes a kernel crash
> when the bitmaps are NULL.
>
> Signed-off-by: Joerg Roedel <[email protected]>
Queued up for 3.18, thanks!
> ---
> kernel/power/snapshot.c | 54
> +++++++++++++++++++++++++++++++++++--------------
> 1 file changed, 39 insertions(+), 15 deletions(-)
>
> diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
> index f1604d8..791a618 100644
> --- a/kernel/power/snapshot.c
> +++ b/kernel/power/snapshot.c
> @@ -725,6 +725,14 @@ static void memory_bm_clear_bit(struct memory_bitmap
> *bm, unsigned long pfn)
> clear_bit(bit, addr);
> }
>
> +static void memory_bm_clear_current(struct memory_bitmap *bm)
> +{
> + int bit;
> +
> + bit = max(bm->cur.node_bit - 1, 0);
> + clear_bit(bit, bm->cur.node->data);
> +}
> +
> static int memory_bm_test_bit(struct memory_bitmap *bm, unsigned long pfn)
> {
> void *addr;
> @@ -1333,23 +1341,39 @@ static struct memory_bitmap copy_bm;
>
> void swsusp_free(void)
> {
> - struct zone *zone;
> - unsigned long pfn, max_zone_pfn;
> + unsigned long fb_pfn, fr_pfn;
>
> - for_each_populated_zone(zone) {
> - max_zone_pfn = zone_end_pfn(zone);
> - for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
> - if (pfn_valid(pfn)) {
> - struct page *page = pfn_to_page(pfn);
> -
> - if (swsusp_page_is_forbidden(page) &&
> - swsusp_page_is_free(page)) {
> - swsusp_unset_page_forbidden(page);
> - swsusp_unset_page_free(page);
> - __free_page(page);
> - }
> - }
> + if (!forbidden_pages_map || !free_pages_map)
> + goto out;
> +
> + memory_bm_position_reset(forbidden_pages_map);
> + memory_bm_position_reset(free_pages_map);
> +
> +loop:
> + fr_pfn = memory_bm_next_pfn(free_pages_map);
> + fb_pfn = memory_bm_next_pfn(forbidden_pages_map);
> +
> + /*
> + * Find the next bit set in both bitmaps. This is guaranteed to
> + * terminate when fb_pfn == fr_pfn == BM_END_OF_MAP.
> + */
> + do {
> + if (fb_pfn < fr_pfn)
> + fb_pfn = memory_bm_next_pfn(forbidden_pages_map);
> + if (fr_pfn < fb_pfn)
> + fr_pfn = memory_bm_next_pfn(free_pages_map);
> + } while (fb_pfn != fr_pfn);
> +
> + if (fr_pfn != BM_END_OF_MAP && pfn_valid(fr_pfn)) {
> + struct page *page = pfn_to_page(fr_pfn);
> +
> + memory_bm_clear_current(forbidden_pages_map);
> + memory_bm_clear_current(free_pages_map);
> + __free_page(page);
> + goto loop;
> }
> +
> +out:
> nr_copy_pages = 0;
> nr_meta_pages = 0;
> restore_pblist = NULL;
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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