Commit b9e60928 authored by Dr. David Alan Gilbert's avatar Dr. David Alan Gilbert Committed by Amit Shah
Browse files

ram_find_and_save_block: Split out the finding 



Split out the finding of the dirty page and all the wrap detection
into a separate function since it was getting a bit hairy.

Signed-off-by: default avatarDr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <1443018431-11170-3-git-send-email-dgilbert@redhat.com>
Reviewed-by: default avatarAmit Shah <amit.shah@redhat.com>

[Fix comment -- Amit]
Signed-off-by: default avatarAmit Shah <amit.shah@redhat.com>
parent b8fb8cb7

migration/ram.c

+59 −25
Original line number Diff line number Diff line
@@ -917,6 +917,59 @@ static int ram_save_compressed_page(QEMUFile *f, RAMBlock *block, 
    return pages;

}



/*

 * Find the next dirty page and update any state associated with

 * the search process.

 *

 * Returns: True if a page is found

 *

 * @f: Current migration stream.

 * @pss: Data about the state of the current dirty page scan.

 * @*again: Set to false if the search has scanned the whole of RAM

 */

static bool find_dirty_block(QEMUFile *f, PageSearchStatus *pss,

                             bool *again)

{

    pss->offset = migration_bitmap_find_and_reset_dirty(pss->block,

                                                       pss->offset);

    if (pss->complete_round && pss->block == last_seen_block &&

        pss->offset >= last_offset) {

        /*

         * We've been once around the RAM and haven't found anything.

         * Give up.

         */

        *again = false;

        return false;

    }

    if (pss->offset >= pss->block->used_length) {

        /* Didn't find anything in this RAM Block */

        pss->offset = 0;

        pss->block = QLIST_NEXT_RCU(pss->block, next);

        if (!pss->block) {

            /* Hit the end of the list */

            pss->block = QLIST_FIRST_RCU(&ram_list.blocks);

            /* Flag that we've looped */

            pss->complete_round = true;

            ram_bulk_stage = false;

            if (migrate_use_xbzrle()) {

                /* If xbzrle is on, stop using the data compression at this

                 * point. In theory, xbzrle can do better than compression.

                 */

                flush_compressed_data(f);

                compression_switch = false;

            }

        }

        /* Didn't find anything this time, but try again on the new block */

        *again = true;

        return false;

    } else {

        /* Can go around again, but... */

        *again = true;

        /* We've found something so probably don't need to */

        return true;

    }

}



/**

 * ram_find_and_save_block: Finds a dirty page and sends it to f

 *
@@ -935,6 +988,7 @@ static int ram_find_and_save_block(QEMUFile *f, bool last_stage, 
{

    PageSearchStatus pss;

    int pages = 0;

    bool again, found;



    pss.block = last_seen_block;

    pss.offset = last_offset;
@@ -944,29 +998,10 @@ static int ram_find_and_save_block(QEMUFile *f, bool last_stage, 
        pss.block = QLIST_FIRST_RCU(&ram_list.blocks);

    }



    while (true) {

        pss.offset = migration_bitmap_find_and_reset_dirty(pss.block,

                                                           pss.offset);

        if (pss.complete_round && pss.block == last_seen_block &&

            pss.offset >= last_offset) {

            break;

        }

        if (pss.offset >= pss.block->used_length) {

            pss.offset = 0;

            pss.block = QLIST_NEXT_RCU(pss.block, next);

            if (!pss.block) {

                pss.block = QLIST_FIRST_RCU(&ram_list.blocks);

                pss.complete_round = true;

                ram_bulk_stage = false;

                if (migrate_use_xbzrle()) {

                    /* If xbzrle is on, stop using the data compression at this

                     * point. In theory, xbzrle can do better than compression.

                     */

                    flush_compressed_data(f);

                    compression_switch = false;

                }

            }

        } else {

    do {

        found = find_dirty_block(f, &pss, &again);



        if (found) {

            if (compression_switch && migrate_use_compression()) {

                pages = ram_save_compressed_page(f, pss.block, pss.offset,

                                                 last_stage,
@@ -979,10 +1014,9 @@ static int ram_find_and_save_block(QEMUFile *f, bool last_stage, 
            /* if page is unmodified, continue to the next */

            if (pages > 0) {

                last_sent_block = pss.block;

                break;

            }

            }

        }

    } while (!pages && again);



    last_seen_block = pss.block;

    last_offset = pss.offset;