Commit f1c72795 authored by Peter Lieven's avatar Peter Lieven Committed by Juan Quintela
Browse files

migration: do not sent zero pages in bulk stage 



during bulk stage of ram migration if a page is a
zero page do not send it at all.
the memory at the destination reads as zero anyway.

even if there is an madvise with QEMU_MADV_DONTNEED
at the target upon receipt of a zero page I have observed
that the target starts swapping if the memory is overcommitted.
it seems that the pages are dropped asynchronously.

this patch also updates QMP to return the number of
skipped pages in MigrationStats.

Signed-off-by: default avatarPeter Lieven <pl@kamp.de>
Reviewed-by: default avatarEric Blake <eblake@redhat.com>
Signed-off-by: default avatarJuan Quintela <quintela@redhat.com>
parent 78d07ae7

arch_init.c

+20 −4
Original line number Diff line number Diff line
@@ -183,6 +183,7 @@ int64_t xbzrle_cache_resize(int64_t new_size) 
/* accounting for migration statistics */

typedef struct AccountingInfo {

    uint64_t dup_pages;

    uint64_t skipped_pages;

    uint64_t norm_pages;

    uint64_t iterations;

    uint64_t xbzrle_bytes;
@@ -208,6 +209,16 @@ uint64_t dup_mig_pages_transferred(void) 
    return acct_info.dup_pages;

}



uint64_t skipped_mig_bytes_transferred(void)

{

    return acct_info.skipped_pages * TARGET_PAGE_SIZE;

}



uint64_t skipped_mig_pages_transferred(void)

{

    return acct_info.skipped_pages;

}



uint64_t norm_mig_bytes_transferred(void)

{

    return acct_info.norm_pages * TARGET_PAGE_SIZE;
@@ -440,10 +451,15 @@ static int ram_save_block(QEMUFile *f, bool last_stage) 
            bytes_sent = -1;

            if (is_zero_page(p)) {

                acct_info.dup_pages++;

                if (!ram_bulk_stage) {

                    bytes_sent = save_block_hdr(f, block, offset, cont,

                                                RAM_SAVE_FLAG_COMPRESS);

                    qemu_put_byte(f, 0);

                    bytes_sent++;

                } else {

                    acct_info.skipped_pages++;

                    bytes_sent = 0;

                }

            } else if (migrate_use_xbzrle()) {

                current_addr = block->offset + offset;

                bytes_sent = save_xbzrle_page(f, p, current_addr, block,

hmp.c

+2 −0
Original line number Diff line number Diff line
@@ -173,6 +173,8 @@ void hmp_info_migrate(Monitor *mon, const QDict *qdict) 
                       info->ram->total >> 10);

        monitor_printf(mon, "duplicate: %" PRIu64 " pages\n",

                       info->ram->duplicate);

        monitor_printf(mon, "skipped: %" PRIu64 " pages\n",

                       info->ram->skipped);

        monitor_printf(mon, "normal: %" PRIu64 " pages\n",

                       info->ram->normal);

        monitor_printf(mon, "normal bytes: %" PRIu64 " kbytes\n",

include/migration/migration.h

+2 −0
Original line number Diff line number Diff line
@@ -96,6 +96,8 @@ extern SaveVMHandlers savevm_ram_handlers; 


uint64_t dup_mig_bytes_transferred(void);

uint64_t dup_mig_pages_transferred(void);

uint64_t skipped_mig_bytes_transferred(void);

uint64_t skipped_mig_pages_transferred(void);

uint64_t norm_mig_bytes_transferred(void);

uint64_t norm_mig_pages_transferred(void);

uint64_t xbzrle_mig_bytes_transferred(void);

migration.c

+2 −1
Original line number Diff line number Diff line
@@ -197,11 +197,11 @@ MigrationInfo *qmp_query_migrate(Error **errp) 
        info->ram->remaining = ram_bytes_remaining();

        info->ram->total = ram_bytes_total();

        info->ram->duplicate = dup_mig_pages_transferred();

        info->ram->skipped = skipped_mig_pages_transferred();

        info->ram->normal = norm_mig_pages_transferred();

        info->ram->normal_bytes = norm_mig_bytes_transferred();

        info->ram->dirty_pages_rate = s->dirty_pages_rate;





        if (blk_mig_active()) {

            info->has_disk = true;

            info->disk = g_malloc0(sizeof(*info->disk));
@@ -227,6 +227,7 @@ MigrationInfo *qmp_query_migrate(Error **errp) 
        info->ram->remaining = 0;

        info->ram->total = ram_bytes_total();

        info->ram->duplicate = dup_mig_pages_transferred();

        info->ram->skipped = skipped_mig_pages_transferred();

        info->ram->normal = norm_mig_pages_transferred();

        info->ram->normal_bytes = norm_mig_bytes_transferred();

        break;

qapi-schema.json

+5 −3
Original line number Diff line number Diff line
@@ -496,7 +496,9 @@ 
#

# @total: total amount of bytes involved in the migration process

#

# @duplicate: number of duplicate pages (since 1.2)

# @duplicate: number of duplicate (zero) pages (since 1.2)

#

# @skipped: number of skipped zero pages (since 1.5)

#

# @normal : number of normal pages (since 1.2)

#
@@ -509,8 +511,8 @@ 
##

{ 'type': 'MigrationStats',

  'data': {'transferred': 'int', 'remaining': 'int', 'total': 'int' ,

           'duplicate': 'int', 'normal': 'int', 'normal-bytes': 'int',

           'dirty-pages-rate' : 'int' } }

           'duplicate': 'int', 'skipped': 'int', 'normal': 'int',

           'normal-bytes': 'int', 'dirty-pages-rate' : 'int' } }



##

# @XBZRLECacheStats