| Message ID | 1587974511-14953-1-git-send-email-wei.w.wang@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] migration/xbzrle: add encoding rate | expand |
* Wei Wang (wei.w.wang@intel.com) wrote: > 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: Yi Sun <yi.y.sun@intel.com> > Signed-off-by: Wei Wang <wei.w.wang@intel.com> > --- > migration/migration.c | 1 + > migration/ram.c | 38 ++++++++++++++++++++++++++++++++++++-- > monitor/hmp-cmds.c | 2 ++ > qapi/migration.json | 5 ++++- > 4 files changed, 43 insertions(+), 3 deletions(-) > > ChangeLog: > - include the 3 bytes (ENCODING_FLAG_XBZRLE flag and encoded_len) when > calculating the encoding rate. Similar to the compress rate > calculation, the 8 byte RAM_SAVE_FLAG_CONTINUE flag isn't included in > the calculation. > > diff --git a/migration/migration.c b/migration/migration.c > index 187ac04..e404213 100644 > --- a/migration/migration.c > +++ b/migration/migration.c > @@ -930,6 +930,7 @@ 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; > } > > diff --git a/migration/ram.c b/migration/ram.c > index 04f13fe..f46ab96 100644 > --- a/migration/ram.c > +++ b/migration/ram.c > @@ -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 */ > @@ -696,6 +700,18 @@ 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++; Can you explain how that works with overflow? Doesn't overflow return -1 here, not increment the bytes, so it looks like you've xbzrle'd a page, but the encoding rate hasn't incremented. Dave > prev_cached_page = get_cached_data(XBZRLE.cache, current_addr); > > /* save current buffer into memory */ > @@ -736,8 +752,12 @@ 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; > @@ -870,9 +890,23 @@ 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()) { > diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c > index 9b94e67..c2a3a66 100644 > --- a/monitor/hmp-cmds.c > +++ b/monitor/hmp-cmds.c > @@ -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); > } > diff --git a/qapi/migration.json b/qapi/migration.json > index eca2981..358e402 100644 > --- a/qapi/migration.json > +++ b/qapi/migration.json > @@ -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 > # } > # } > -- > 1.8.3.1 > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
On 04/28/2020 10:51 PM, Dr. David Alan Gilbert wrote: > * Wei Wang (wei.w.wang@intel.com) wrote: >> 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: Yi Sun <yi.y.sun@intel.com> >> Signed-off-by: Wei Wang <wei.w.wang@intel.com> >> --- >> migration/migration.c | 1 + >> migration/ram.c | 38 ++++++++++++++++++++++++++++++++++++-- >> monitor/hmp-cmds.c | 2 ++ >> qapi/migration.json | 5 ++++- >> 4 files changed, 43 insertions(+), 3 deletions(-) >> >> ChangeLog: >> - include the 3 bytes (ENCODING_FLAG_XBZRLE flag and encoded_len) when >> calculating the encoding rate. Similar to the compress rate >> calculation, the 8 byte RAM_SAVE_FLAG_CONTINUE flag isn't included in >> the calculation. >> >> diff --git a/migration/migration.c b/migration/migration.c >> index 187ac04..e404213 100644 >> --- a/migration/migration.c >> +++ b/migration/migration.c >> @@ -930,6 +930,7 @@ 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; >> } >> >> diff --git a/migration/ram.c b/migration/ram.c >> index 04f13fe..f46ab96 100644 >> --- a/migration/ram.c >> +++ b/migration/ram.c >> @@ -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 */ >> @@ -696,6 +700,18 @@ 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++; > Can you explain how that works with overflow? Doesn't overflow return > -1 here, not increment the bytes, so it looks like you've xbzrle'd a > page, but the encoding rate hasn't incremented. OK. How about adding below before returning -1 (for the overflow case): ... xbzrle_counters.bytes += TARGET_PAGE_SIZE; return -1; Example: if we have 2 pages encoded as below: 4KB--> after normal encoding: 2KB 4KB--> after overflow: 4KB (will be sent as non-encoded page) then the encoding rate is 8KB / 6KB = ~1.3 (if we skip the counting of the overflow case, the encoding rate will be 4KB/ 2KB=2. Users may think that's good to go with xbzrle, unless they do another calculation with checking the overflow numbers themselves) Best, Wei
* Wei Wang (wei.w.wang@intel.com) wrote: > On 04/28/2020 10:51 PM, Dr. David Alan Gilbert wrote: > > * Wei Wang (wei.w.wang@intel.com) wrote: > > > 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: Yi Sun <yi.y.sun@intel.com> > > > Signed-off-by: Wei Wang <wei.w.wang@intel.com> > > > --- > > > migration/migration.c | 1 + > > > migration/ram.c | 38 ++++++++++++++++++++++++++++++++++++-- > > > monitor/hmp-cmds.c | 2 ++ > > > qapi/migration.json | 5 ++++- > > > 4 files changed, 43 insertions(+), 3 deletions(-) > > > > > > ChangeLog: > > > - include the 3 bytes (ENCODING_FLAG_XBZRLE flag and encoded_len) when > > > calculating the encoding rate. Similar to the compress rate > > > calculation, the 8 byte RAM_SAVE_FLAG_CONTINUE flag isn't included in > > > the calculation. > > > > > > diff --git a/migration/migration.c b/migration/migration.c > > > index 187ac04..e404213 100644 > > > --- a/migration/migration.c > > > +++ b/migration/migration.c > > > @@ -930,6 +930,7 @@ 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; > > > } > > > diff --git a/migration/ram.c b/migration/ram.c > > > index 04f13fe..f46ab96 100644 > > > --- a/migration/ram.c > > > +++ b/migration/ram.c > > > @@ -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 */ > > > @@ -696,6 +700,18 @@ 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++; > > Can you explain how that works with overflow? Doesn't overflow return > > -1 here, not increment the bytes, so it looks like you've xbzrle'd a > > page, but the encoding rate hasn't incremented. > > OK. How about adding below before returning -1 (for the overflow case): > > ... > xbzrle_counters.bytes += TARGET_PAGE_SIZE; > return -1; Yes, I think that feels better. Dave > Example: if we have 2 pages encoded as below: > 4KB--> after normal encoding: 2KB > 4KB--> after overflow: 4KB (will be sent as non-encoded page) > then the encoding rate is 8KB / 6KB = ~1.3 > (if we skip the counting of the overflow case, > the encoding rate will be 4KB/ 2KB=2. Users may think that's > good to go with xbzrle, unless they do another calculation with > checking the overflow numbers themselves) > > Best, > Wei > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
diff --git a/migration/migration.c b/migration/migration.c index 187ac04..e404213 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -930,6 +930,7 @@ 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; } diff --git a/migration/ram.c b/migration/ram.c index 04f13fe..f46ab96 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -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 */ @@ -696,6 +700,18 @@ 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 */ @@ -736,8 +752,12 @@ 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; @@ -870,9 +890,23 @@ 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()) { diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c index 9b94e67..c2a3a66 100644 --- a/monitor/hmp-cmds.c +++ b/monitor/hmp-cmds.c @@ -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); } diff --git a/qapi/migration.json b/qapi/migration.json index eca2981..358e402 100644 --- a/qapi/migration.json +++ b/qapi/migration.json @@ -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 # } # }