Commit e460a4b1 authored by Wei Wang's avatar Wei Wang Committed by Dr. David Alan Gilbert
Browse files

migration/xbzrle: add encoding rate 



Users may need to check the xbzrle encoding rate to know if the guest
memory is xbzrle encoding-friendly, and dynamically turn off the
encoding if the encoding rate is low.

Signed-off-by: default avatarYi Sun <yi.y.sun@intel.com>
Signed-off-by: default avatarWei Wang <wei.w.wang@intel.com>
Message-Id: <1588208375-19556-1-git-send-email-wei.w.wang@intel.com>
Reviewed-by: default avatarDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: default avatarDr. David Alan Gilbert <dgilbert@redhat.com>
parent 59c59c67

migration/migration.c

+1 −0
Original line number Diff line number Diff line
@@ -932,6 +932,7 @@ static void populate_ram_info(MigrationInfo *info, MigrationState *s) 
        info->xbzrle_cache->pages = xbzrle_counters.pages;

        info->xbzrle_cache->cache_miss = xbzrle_counters.cache_miss;

        info->xbzrle_cache->cache_miss_rate = xbzrle_counters.cache_miss_rate;

        info->xbzrle_cache->encoding_rate = xbzrle_counters.encoding_rate;

        info->xbzrle_cache->overflow = xbzrle_counters.overflow;

    }

migration/ram.c

+37 −2
Original line number Diff line number Diff line
@@ -327,6 +327,10 @@ struct RAMState { 
    uint64_t num_dirty_pages_period;

    /* xbzrle misses since the beginning of the period */

    uint64_t xbzrle_cache_miss_prev;

    /* Amount of xbzrle pages since the beginning of the period */

    uint64_t xbzrle_pages_prev;

    /* Amount of xbzrle encoded bytes since the beginning of the period */

    uint64_t xbzrle_bytes_prev;



    /* compression statistics since the beginning of the period */

    /* amount of count that no free thread to compress data */
@@ -710,6 +714,18 @@ static int save_xbzrle_page(RAMState *rs, uint8_t **current_data, 
        return -1;

    }



    /*

     * Reaching here means the page has hit the xbzrle cache, no matter what

     * encoding result it is (normal encoding, overflow or skipping the page),

     * count the page as encoded. This is used to caculate the encoding rate.

     *

     * Example: 2 pages (8KB) being encoded, first page encoding generates 2KB,

     * 2nd page turns out to be skipped (i.e. no new bytes written to the

     * page), the overall encoding rate will be 8KB / 2KB = 4, which has the

     * skipped page included. In this way, the encoding rate can tell if the

     * guest page is good for xbzrle encoding.

     */

    xbzrle_counters.pages++;

    prev_cached_page = get_cached_data(XBZRLE.cache, current_addr);



    /* save current buffer into memory */
@@ -740,6 +756,7 @@ static int save_xbzrle_page(RAMState *rs, uint8_t **current_data, 
    } else if (encoded_len == -1) {

        trace_save_xbzrle_page_overflow();

        xbzrle_counters.overflow++;

        xbzrle_counters.bytes += TARGET_PAGE_SIZE;

        return -1;

    }
@@ -750,8 +767,12 @@ static int save_xbzrle_page(RAMState *rs, uint8_t **current_data, 
    qemu_put_be16(rs->f, encoded_len);

    qemu_put_buffer(rs->f, XBZRLE.encoded_buf, encoded_len);

    bytes_xbzrle += encoded_len + 1 + 2;

    xbzrle_counters.pages++;

    xbzrle_counters.bytes += bytes_xbzrle;

    /*

     * Like compressed_size (please see update_compress_thread_counts),

     * the xbzrle encoded bytes don't count the 8 byte header with

     * RAM_SAVE_FLAG_CONTINUE.

     */

    xbzrle_counters.bytes += bytes_xbzrle - 8;

    ram_counters.transferred += bytes_xbzrle;



    return 1;
@@ -884,9 +905,23 @@ static void migration_update_rates(RAMState *rs, int64_t end_time) 
    }



    if (migrate_use_xbzrle()) {

        double encoded_size, unencoded_size;



        xbzrle_counters.cache_miss_rate = (double)(xbzrle_counters.cache_miss -

            rs->xbzrle_cache_miss_prev) / page_count;

        rs->xbzrle_cache_miss_prev = xbzrle_counters.cache_miss;

        unencoded_size = (xbzrle_counters.pages - rs->xbzrle_pages_prev) *

                         TARGET_PAGE_SIZE;

        encoded_size = xbzrle_counters.bytes - rs->xbzrle_bytes_prev;

        if (xbzrle_counters.pages == rs->xbzrle_pages_prev) {

            xbzrle_counters.encoding_rate = 0;

        } else if (!encoded_size) {

            xbzrle_counters.encoding_rate = UINT64_MAX;

        } else {

            xbzrle_counters.encoding_rate = unencoded_size / encoded_size;

        }

        rs->xbzrle_pages_prev = xbzrle_counters.pages;

        rs->xbzrle_bytes_prev = xbzrle_counters.bytes;

    }



    if (migrate_use_compression()) {

monitor/hmp-cmds.c

+2 −0
Original line number Diff line number Diff line
@@ -303,6 +303,8 @@ void hmp_info_migrate(Monitor *mon, const QDict *qdict) 
                       info->xbzrle_cache->cache_miss);

        monitor_printf(mon, "xbzrle cache miss rate: %0.2f\n",

                       info->xbzrle_cache->cache_miss_rate);

        monitor_printf(mon, "xbzrle encoding rate: %0.2f\n",

                       info->xbzrle_cache->encoding_rate);

        monitor_printf(mon, "xbzrle overflow: %" PRIu64 "\n",

                       info->xbzrle_cache->overflow);

    }

qapi/migration.json

+4 −1
Original line number Diff line number Diff line
@@ -70,6 +70,8 @@ 
#

# @cache-miss-rate: rate of cache miss (since 2.1)

#

# @encoding-rate: rate of encoded bytes (since 5.1)

#

# @overflow: number of overflows

#

# Since: 1.2
@@ -77,7 +79,7 @@ 
{ 'struct': 'XBZRLECacheStats',

  'data': {'cache-size': 'int', 'bytes': 'int', 'pages': 'int',

           'cache-miss': 'int', 'cache-miss-rate': 'number',

           'overflow': 'int' } }

           'encoding-rate': 'number', 'overflow': 'int' } }



##

# @CompressionStats:
@@ -337,6 +339,7 @@ 
#             "pages":2444343,

#             "cache-miss":2244,

#             "cache-miss-rate":0.123,

#             "encoding-rate":80.1,

#             "overflow":34434

#          }

#       }