Re: [Qemu-devel] [PATCH 51/54] ram: Use ramblock and page offset instead of absolute offset

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Juan Quintela (quintela@redhat.com) wrote:
> This removes the needto pass also the absolute offset.
> 
> Signed-off-by: Juan Quintela <quintela@redhat.com>

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  migration/ram.c | 65 ++++++++++++++++++++++++---------------------------------
>  1 file changed, 27 insertions(+), 38 deletions(-)
> 
> diff --git a/migration/ram.c b/migration/ram.c
> index 4132503..fc1f08f 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -609,12 +609,10 @@ static int save_xbzrle_page(RAMState *rs, uint8_t **current_data,
>   * @rs: current RAM state
>   * @rb: RAMBlock where to search for dirty pages
>   * @start: page where we start the search
> - * @page_abs: pointer into where to store the dirty page
>   */
>  static inline
>  unsigned long migration_bitmap_find_dirty(RAMState *rs, RAMBlock *rb,
> -                                          unsigned long start,
> -                                          unsigned long *page_abs)
> +                                          unsigned long start)
>  {
>      unsigned long base = rb->offset >> TARGET_PAGE_BITS;
>      unsigned long nr = base + start;
> @@ -631,17 +629,18 @@ unsigned long migration_bitmap_find_dirty(RAMState *rs, RAMBlock *rb,
>          next = find_next_bit(bitmap, size, nr);
>      }
>  
> -    *page_abs = next;
>      return next - base;
>  }
>  
>  static inline bool migration_bitmap_clear_dirty(RAMState *rs,
> -                                                unsigned long page_abs)
> +                                                RAMBlock *rb,
> +                                                unsigned long page)
>  {
>      bool ret;
>      unsigned long *bitmap = atomic_rcu_read(&rs->ram_bitmap)->bmap;
> +    unsigned long nr = (rb->offset >> TARGET_PAGE_BITS) + page;
>  
> -    ret = test_and_clear_bit(page_abs, bitmap);
> +    ret = test_and_clear_bit(nr, bitmap);
>  
>      if (ret) {
>          rs->migration_dirty_pages--;
> @@ -1053,13 +1052,10 @@ static int ram_save_compressed_page(RAMState *rs, PageSearchStatus *pss,
>   * @rs: current RAM state
>   * @pss: data about the state of the current dirty page scan
>   * @again: set to false if the search has scanned the whole of RAM
> - * @page_abs: pointer into where to store the dirty page
>   */
> -static bool find_dirty_block(RAMState *rs, PageSearchStatus *pss,
> -                             bool *again, unsigned long *page_abs)
> +static bool find_dirty_block(RAMState *rs, PageSearchStatus *pss, bool *again)
>  {
> -    pss->page = migration_bitmap_find_dirty(rs, pss->block, pss->page,
> -                                            page_abs);
> +    pss->page = migration_bitmap_find_dirty(rs, pss->block, pss->page);
>      if (pss->complete_round && pss->block == rs->last_seen_block &&
>          pss->page >= rs->last_page) {
>          /*
> @@ -1106,10 +1102,8 @@ static bool find_dirty_block(RAMState *rs, PageSearchStatus *pss,
>   *
>   * @rs: current RAM state
>   * @offset: used to return the offset within the RAMBlock
> - * @page_abs: pointer into where to store the dirty page
>   */
> -static RAMBlock *unqueue_page(RAMState *rs, ram_addr_t *offset,
> -                              unsigned long *page_abs)
> +static RAMBlock *unqueue_page(RAMState *rs, ram_addr_t *offset)
>  {
>      RAMBlock *block = NULL;
>  
> @@ -1119,7 +1113,6 @@ static RAMBlock *unqueue_page(RAMState *rs, ram_addr_t *offset,
>                                  QSIMPLEQ_FIRST(&rs->src_page_requests);
>          block = entry->rb;
>          *offset = entry->offset;
> -        *page_abs = (entry->offset + entry->rb->offset) >> TARGET_PAGE_BITS;
>  
>          if (entry->len > TARGET_PAGE_SIZE) {
>              entry->len -= TARGET_PAGE_SIZE;
> @@ -1144,17 +1137,15 @@ static RAMBlock *unqueue_page(RAMState *rs, ram_addr_t *offset,
>   *
>   * @rs: current RAM state
>   * @pss: data about the state of the current dirty page scan
> - * @page_abs: pointer into where to store the dirty page
>   */
> -static bool get_queued_page(RAMState *rs, PageSearchStatus *pss,
> -                            unsigned long *page_abs)
> +static bool get_queued_page(RAMState *rs, PageSearchStatus *pss)
>  {
>      RAMBlock  *block;
>      ram_addr_t offset;
>      bool dirty;
>  
>      do {
> -        block = unqueue_page(rs, &offset, page_abs);
> +        block = unqueue_page(rs, &offset);
>          /*
>           * We're sending this page, and since it's postcopy nothing else
>           * will dirty it, and we must make sure it doesn't get sent again
> @@ -1163,16 +1154,18 @@ static bool get_queued_page(RAMState *rs, PageSearchStatus *pss,
>           */
>          if (block) {
>              unsigned long *bitmap;
> +            unsigned long page;
> +
>              bitmap = atomic_rcu_read(&rs->ram_bitmap)->bmap;
> -            dirty = test_bit(*page_abs, bitmap);
> +            page = (block->offset + offset) >> TARGET_PAGE_BITS;
> +            dirty = test_bit(page, bitmap);
>              if (!dirty) {
>                  trace_get_queued_page_not_dirty(block->idstr, (uint64_t)offset,
> -                    *page_abs,
> -                    test_bit(*page_abs,
> +                    page,
> +                    test_bit(page,
>                               atomic_rcu_read(&rs->ram_bitmap)->unsentmap));
>              } else {
> -                trace_get_queued_page(block->idstr, (uint64_t)offset,
> -                                     *page_abs);
> +                trace_get_queued_page(block->idstr, (uint64_t)offset, page);
>              }
>          }
>  
> @@ -1300,22 +1293,22 @@ err:
>   * @ms: current migration state
>   * @pss: data about the page we want to send
>   * @last_stage: if we are at the completion stage
> - * @page_abs: page number of the dirty page
>   */
>  static int ram_save_target_page(RAMState *rs, PageSearchStatus *pss,
> -                                bool last_stage, unsigned long page_abs)
> +                                bool last_stage)
>  {
>      int res = 0;
>  
>      /* Check the pages is dirty and if it is send it */
> -    if (migration_bitmap_clear_dirty(rs, page_abs)) {
> +    if (migration_bitmap_clear_dirty(rs, pss->block, pss->page)) {
>          unsigned long *unsentmap;
>          /*
>           * If xbzrle is on, stop using the data compression after first
>           * round of migration even if compression is enabled. In theory,
>           * xbzrle can do better than compression.
>           */
> -
> +        unsigned long page =
> +            (pss->block->offset >> TARGET_PAGE_BITS) + pss->page;
>          if (migrate_use_compression()
>              && (rs->ram_bulk_stage || !migrate_use_xbzrle())) {
>              res = ram_save_compressed_page(rs, pss, last_stage);
> @@ -1328,7 +1321,7 @@ static int ram_save_target_page(RAMState *rs, PageSearchStatus *pss,
>          }
>          unsentmap = atomic_rcu_read(&rs->ram_bitmap)->unsentmap;
>          if (unsentmap) {
> -            clear_bit(page_abs, unsentmap);
> +            clear_bit(page, unsentmap);
>          }
>      }
>  
> @@ -1350,25 +1343,22 @@ static int ram_save_target_page(RAMState *rs, PageSearchStatus *pss,
>   * @ms: current migration state
>   * @pss: data about the page we want to send
>   * @last_stage: if we are at the completion stage
> - * @page_abs: Page number of the dirty page
>   */
>  static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss,
> -                              bool last_stage,
> -                              unsigned long page_abs)
> +                              bool last_stage)
>  {
>      int tmppages, pages = 0;
>      size_t pagesize_bits =
>          qemu_ram_pagesize(pss->block) >> TARGET_PAGE_BITS;
>  
>      do {
> -        tmppages = ram_save_target_page(rs, pss, last_stage, page_abs);
> +        tmppages = ram_save_target_page(rs, pss, last_stage);
>          if (tmppages < 0) {
>              return tmppages;
>          }
>  
>          pages += tmppages;
>          pss->page++;
> -        page_abs++;
>      } while (pss->page & (pagesize_bits - 1));
>  
>      /* The offset we leave with is the last one we looked at */
> @@ -1395,7 +1385,6 @@ static int ram_find_and_save_block(RAMState *rs, bool last_stage)
>      PageSearchStatus pss;
>      int pages = 0;
>      bool again, found;
> -    unsigned long page_abs; /* Page number of the dirty page */
>  
>      /* No dirty page as there is zero RAM */
>      if (!ram_bytes_total()) {
> @@ -1412,15 +1401,15 @@ static int ram_find_and_save_block(RAMState *rs, bool last_stage)
>  
>      do {
>          again = true;
> -        found = get_queued_page(rs, &pss, &page_abs);
> +        found = get_queued_page(rs, &pss);
>  
>          if (!found) {
>              /* priority queue empty, so just search for something dirty */
> -            found = find_dirty_block(rs, &pss, &again, &page_abs);
> +            found = find_dirty_block(rs, &pss, &again);
>          }
>  
>          if (found) {
> -            pages = ram_save_host_page(rs, &pss, last_stage, page_abs);
> +            pages = ram_save_host_page(rs, &pss, last_stage);
>          }
>      } while (!pages && again);
>  
> -- 
> 2.9.3
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK