* Wei Wang (wei.w.w...@intel.com) wrote:
> Like compressed_size which indicates how many bytes are compressed, we
> need encoded_size to understand how many bytes are encoded with xbzrle
> during migration.
>
> Replace the old xbzrle_counter.bytes, instead of adding a new counter,
> because we don't find a usage of xbzrle_counter.bytes currently, which
> includes 3 more bytes of the migration transfer protocol header (in
> addition to the encoding header). The encoded_size will further be used
> to calculate the encoding rate.
>
> Signed-off-by: Yi Sun <yi.y....@intel.com>
> Signed-off-by: Wei Wang <wei.w.w...@intel.com>
Can you explain why these 3 bytes matter? Certainly the 2 bytes of the
encoded_len are an overhead that's a cost of using XBZRLE; so if you're
trying to figure out whether xbzrle is worth it, then you should include
those 2 bytes in the cost.
That other byte, that holds ENCODING_FLAG_XBZRLE also seems to be pure
oerhead of XBZRLE; so your cost of using XBZRLE really does include
those 3 bytes.
SO to me it makes sense to include the 3 bytes as it currently does.
Dave
> ---
> migration/migration.c | 2 +-
> migration/ram.c | 18 +++++++++---------
> monitor/hmp-cmds.c | 4 ++--
> qapi/migration.json | 6 +++---
> 4 files changed, 15 insertions(+), 15 deletions(-)
>
> diff --git a/migration/migration.c b/migration/migration.c
> index 187ac0410c..8e7ee0d76b 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -926,7 +926,7 @@ static void populate_ram_info(MigrationInfo *info,
> MigrationState *s)
> info->has_xbzrle_cache = true;
> info->xbzrle_cache = g_malloc0(sizeof(*info->xbzrle_cache));
> info->xbzrle_cache->cache_size = migrate_xbzrle_cache_size();
> - info->xbzrle_cache->bytes = xbzrle_counters.bytes;
> + info->xbzrle_cache->encoded_size = xbzrle_counters.encoded_size;
> 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;
> diff --git a/migration/ram.c b/migration/ram.c
> index 04f13feb2e..bca5878f25 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -677,7 +677,7 @@ static int save_xbzrle_page(RAMState *rs, uint8_t
> **current_data,
> ram_addr_t current_addr, RAMBlock *block,
> ram_addr_t offset, bool last_stage)
> {
> - int encoded_len = 0, bytes_xbzrle;
> + int encoded_size = 0, bytes_xbzrle;
> uint8_t *prev_cached_page;
>
> if (!cache_is_cached(XBZRLE.cache, current_addr,
> @@ -702,7 +702,7 @@ static int save_xbzrle_page(RAMState *rs, uint8_t
> **current_data,
> memcpy(XBZRLE.current_buf, *current_data, TARGET_PAGE_SIZE);
>
> /* XBZRLE encoding (if there is no overflow) */
> - encoded_len = xbzrle_encode_buffer(prev_cached_page, XBZRLE.current_buf,
> + encoded_size = xbzrle_encode_buffer(prev_cached_page, XBZRLE.current_buf,
> TARGET_PAGE_SIZE, XBZRLE.encoded_buf,
> TARGET_PAGE_SIZE);
>
> @@ -710,7 +710,7 @@ static int save_xbzrle_page(RAMState *rs, uint8_t
> **current_data,
> * Update the cache contents, so that it corresponds to the data
> * sent, in all cases except where we skip the page.
> */
> - if (!last_stage && encoded_len != 0) {
> + if (!last_stage && encoded_size != 0) {
> memcpy(prev_cached_page, XBZRLE.current_buf, TARGET_PAGE_SIZE);
> /*
> * In the case where we couldn't compress, ensure that the caller
> @@ -720,10 +720,10 @@ static int save_xbzrle_page(RAMState *rs, uint8_t
> **current_data,
> *current_data = prev_cached_page;
> }
>
> - if (encoded_len == 0) {
> + if (encoded_size == 0) {
> trace_save_xbzrle_page_skipping();
> return 0;
> - } else if (encoded_len == -1) {
> + } else if (encoded_size == -1) {
> trace_save_xbzrle_page_overflow();
> xbzrle_counters.overflow++;
> return -1;
> @@ -733,11 +733,11 @@ static int save_xbzrle_page(RAMState *rs, uint8_t
> **current_data,
> bytes_xbzrle = save_page_header(rs, rs->f, block,
> offset | RAM_SAVE_FLAG_XBZRLE);
> qemu_put_byte(rs->f, ENCODING_FLAG_XBZRLE);
> - qemu_put_be16(rs->f, encoded_len);
> - qemu_put_buffer(rs->f, XBZRLE.encoded_buf, encoded_len);
> - bytes_xbzrle += encoded_len + 1 + 2;
> + qemu_put_be16(rs->f, encoded_size);
> + qemu_put_buffer(rs->f, XBZRLE.encoded_buf, encoded_size);
> + bytes_xbzrle += encoded_size + 1 + 2;
> xbzrle_counters.pages++;
> - xbzrle_counters.bytes += bytes_xbzrle;
> + xbzrle_counters.encoded_size += encoded_size;
> ram_counters.transferred += bytes_xbzrle;
>
> return 1;
> diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
> index 9b94e67879..6d3b35ca64 100644
> --- a/monitor/hmp-cmds.c
> +++ b/monitor/hmp-cmds.c
> @@ -295,8 +295,8 @@ void hmp_info_migrate(Monitor *mon, const QDict *qdict)
> if (info->has_xbzrle_cache) {
> monitor_printf(mon, "cache size: %" PRIu64 " bytes\n",
> info->xbzrle_cache->cache_size);
> - monitor_printf(mon, "xbzrle transferred: %" PRIu64 " kbytes\n",
> - info->xbzrle_cache->bytes >> 10);
> + monitor_printf(mon, "xbzrle encoded size: %" PRIu64 " kbytes\n",
> + info->xbzrle_cache->encoded_size >> 10);
> monitor_printf(mon, "xbzrle pages: %" PRIu64 " pages\n",
> info->xbzrle_cache->pages);
> monitor_printf(mon, "xbzrle cache miss: %" PRIu64 "\n",
> diff --git a/qapi/migration.json b/qapi/migration.json
> index eca2981d0a..bf195ff6ac 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -62,7 +62,7 @@
> #
> # @cache-size: XBZRLE cache size
> #
> -# @bytes: amount of bytes already transferred to the target VM
> +# @encoded_size: amount of bytes encoded
> #
> # @pages: amount of pages transferred to the target VM
> #
> @@ -75,7 +75,7 @@
> # Since: 1.2
> ##
> { 'struct': 'XBZRLECacheStats',
> - 'data': {'cache-size': 'int', 'bytes': 'int', 'pages': 'int',
> + 'data': {'cache-size': 'int', 'encoded_size': 'int', 'pages': 'int',
> 'cache-miss': 'int', 'cache-miss-rate': 'number',
> 'overflow': 'int' } }
>
> @@ -333,7 +333,7 @@
> # },
> # "xbzrle-cache":{
> # "cache-size":67108864,
> -# "bytes":20971520,
> +# "encoded_size":20971520,
> # "pages":2444343,
> # "cache-miss":2244,
> # "cache-miss-rate":0.123,
> --
> 2.20.1
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
