Re: [PATCH v1 2/2] migration/xbzrle: add encoding rate
On 04/20/2020 10:53 PM, Eric Blake wrote: On 4/19/20 10:06 PM, Wei Wang 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 Signed-off-by: Wei Wang --- In addition to Dan's review comments, +++ b/qapi/migration.json @@ -70,6 +70,8 @@ # # @cache-miss-rate: rate of cache miss (since 2.1) # +# @encoding-rate: rate of cache miss This is missing a '(since 5.1)' tag. OK, will add it, thanks. Best, Wei
Re: [PATCH v1 2/2] migration/xbzrle: add encoding rate
On 4/19/20 10:06 PM, Wei Wang 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
Signed-off-by: Wei Wang
---
In addition to Dan's review comments,
+++ b/qapi/migration.json
@@ -70,6 +70,8 @@
#
# @cache-miss-rate: rate of cache miss (since 2.1)
#
+# @encoding-rate: rate of cache miss
This is missing a '(since 5.1)' tag.
+#
# @overflow: number of overflows
#
# Since: 1.2
@@ -77,7 +79,7 @@
{ 'struct': 'XBZRLECacheStats',
'data': {'cache-size': 'int', 'encoded_size': '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
# }
# }
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
Re: [PATCH v1 2/2] migration/xbzrle: add encoding rate
On Mon, Apr 20, 2020 at 11:06:43AM +0800, Wei Wang 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
> Signed-off-by: Wei Wang
> ---
> migration/migration.c | 1 +
> migration/ram.c | 31 +--
> monitor/hmp-cmds.c| 2 ++
> qapi/migration.json | 5 -
> slirp | 2 +-
> 5 files changed, 37 insertions(+), 4 deletions(-)
>
> diff --git a/migration/migration.c b/migration/migration.c
> index 8e7ee0d76b..84a556a4ac 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 bca5878f25..c87c38ec80 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 encoded bytes since the beginning of the period */
> +uint64_t encoded_size_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 */
> @@ -736,7 +752,6 @@ static int save_xbzrle_page(RAMState *rs, uint8_t
> **current_data,
> 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.encoded_size += encoded_size;
> ram_counters.transferred += bytes_xbzrle;
>
> @@ -859,7 +874,7 @@ uint64_t ram_get_total_transferred_pages(void)
> static void migration_update_rates(RAMState *rs, int64_t end_time)
> {
> uint64_t page_count = rs->target_page_count - rs->target_page_count_prev;
> -double compressed_size;
> +double compressed_size, encoded_size, unencoded_size;
>
> /* calculate period counters */
> ram_counters.dirty_pages_rate = rs->num_dirty_pages_period * 1000
> @@ -873,6 +888,18 @@ static void migration_update_rates(RAMState *rs, int64_t
> end_time)
> 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.encoded_size - rs->encoded_size_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->encoded_size_prev = xbzrle_counters.encoded_size;
> }
>
> if (migrate_use_compression()) {
> diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
> index 6d3b35ca64..07f41e582f 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",
>
[PATCH v1 2/2] 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: Yi Sun
Signed-off-by: Wei Wang
---
migration/migration.c | 1 +
migration/ram.c | 31 +--
monitor/hmp-cmds.c| 2 ++
qapi/migration.json | 5 -
slirp | 2 +-
5 files changed, 37 insertions(+), 4 deletions(-)
diff --git a/migration/migration.c b/migration/migration.c
index 8e7ee0d76b..84a556a4ac 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 bca5878f25..c87c38ec80 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 encoded bytes since the beginning of the period */
+uint64_t encoded_size_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 */
@@ -736,7 +752,6 @@ static int save_xbzrle_page(RAMState *rs, uint8_t
**current_data,
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.encoded_size += encoded_size;
ram_counters.transferred += bytes_xbzrle;
@@ -859,7 +874,7 @@ uint64_t ram_get_total_transferred_pages(void)
static void migration_update_rates(RAMState *rs, int64_t end_time)
{
uint64_t page_count = rs->target_page_count - rs->target_page_count_prev;
-double compressed_size;
+double compressed_size, encoded_size, unencoded_size;
/* calculate period counters */
ram_counters.dirty_pages_rate = rs->num_dirty_pages_period * 1000
@@ -873,6 +888,18 @@ static void migration_update_rates(RAMState *rs, int64_t
end_time)
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.encoded_size - rs->encoded_size_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->encoded_size_prev = xbzrle_counters.encoded_size;
}
if (migrate_use_compression()) {
diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
index 6d3b35ca64..07f41e582f 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
