Commit ced1c616 authored by Pavel Butsykin's avatar Pavel Butsykin Committed by Dr. David Alan Gilbert
Browse files

migration: discard non-dirty ram pages after the start of postcopy 



After the start of postcopy migration there are some non-dirty pages which have
already been migrated. These pages are no longer needed on the source vm so that
we can free them and it doen't hurt to complete the migration.

Signed-off-by: default avatarPavel Butsykin <pbutsykin@virtuozzo.com>
Message-Id: <20170203152321.19739-4-pbutsykin@virtuozzo.com>
Signed-off-by: default avatarDr. David Alan Gilbert <dgilbert@redhat.com>
parent 53f09a10

include/migration/migration.h

+1 −0
Original line number Diff line number Diff line
@@ -285,6 +285,7 @@ int ram_postcopy_send_discard_bitmap(MigrationState *ms); 
int ram_discard_range(MigrationIncomingState *mis, const char *block_name,

                      uint64_t start, size_t length);

int ram_postcopy_incoming_init(MigrationIncomingState *mis);

void ram_postcopy_migrated_memory_release(MigrationState *ms);



/**

 * @migrate_add_blocker - prevent migration from proceeding

migration/migration.c

+4 −0
Original line number Diff line number Diff line
@@ -1722,6 +1722,10 @@ static int postcopy_start(MigrationState *ms, bool *old_vm_running) 
     */

    qemu_savevm_send_ping(ms->to_dst_file, 4);



    if (migrate_release_ram()) {

        ram_postcopy_migrated_memory_release(ms);

    }



    ret = qemu_file_get_error(ms->to_dst_file);

    if (ret) {

        error_report("postcopy_start: Migration stream errored");

migration/ram.c

+19 −0
Original line number Diff line number Diff line
@@ -1537,6 +1537,25 @@ void ram_debug_dump_bitmap(unsigned long *todump, bool expected) 


/* **** functions for postcopy ***** */



void ram_postcopy_migrated_memory_release(MigrationState *ms)

{

    struct RAMBlock *block;

    unsigned long *bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap;



    QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {

        unsigned long first = block->offset >> TARGET_PAGE_BITS;

        unsigned long range = first + (block->used_length >> TARGET_PAGE_BITS);

        unsigned long run_start = find_next_zero_bit(bitmap, range, first);



        while (run_start < range) {

            unsigned long run_end = find_next_bit(bitmap, range, run_start + 1);

            ram_discard_range(NULL, block->idstr, run_start << TARGET_PAGE_BITS,

                              (run_end - run_start) << TARGET_PAGE_BITS);

            run_start = find_next_zero_bit(bitmap, range, run_end + 1);

        }

    }

}



/*

 * Callback from postcopy_each_ram_send_discard for each RAMBlock

 * Note: At this point the 'unsentmap' is the processed bitmap combined