In sampling mode, a new metric is collected and reported:
number of pages entirely filled with zeroes.
Signed-off-by: Andrei Gudkov <gudkov.and...@huawei.com>
---
migration/dirtyrate.c | 40 +++++++++++++++++++++++++++++++++++-----
migration/dirtyrate.h | 1 +
qapi/migration.json | 4 ++++
3 files changed, 40 insertions(+), 5 deletions(-)
diff --git a/migration/dirtyrate.c b/migration/dirtyrate.c
index 4491bbe91a..55ef69927e 100644
--- a/migration/dirtyrate.c
+++ b/migration/dirtyrate.c
@@ -258,6 +258,9 @@ static struct DirtyRateInfo *query_dirty_rate_info(void)
info->n_sampled_pages = DirtyStat.page_sampling.n_sampled_pages;
info->has_n_sampled_pages = true;
+ info->n_zero_pages = DirtyStat.page_sampling.n_zero_pages;
+ info->has_n_zero_pages = true;
+
for (i = 0; i < DirtyStat.page_sampling.n_readings; i++) {
DirtyReading *dr = &DirtyStat.page_sampling.readings[i];
QAPI_LIST_APPEND(periods_tail, dr->period);
@@ -291,6 +294,7 @@ static void init_dirtyrate_stat(int64_t start_time,
case DIRTY_RATE_MEASURE_MODE_PAGE_SAMPLING:
DirtyStat.page_sampling.n_total_pages = 0;
DirtyStat.page_sampling.n_sampled_pages = 0;
+ DirtyStat.page_sampling.n_zero_pages = 0;
DirtyStat.page_sampling.n_readings = 0;
DirtyStat.page_sampling.readings = g_try_malloc0_n(MAX_DIRTY_READINGS,
sizeof(DirtyReading));
@@ -319,6 +323,7 @@ static void cleanup_dirtyrate_stat(struct DirtyRateConfig
config)
/*
* Compute hash of a single page of size TARGET_PAGE_SIZE.
+ * If ptr is NULL, then compute hash of a page entirely filled with zeros.
*/
static uint32_t compute_page_hash(void *ptr)
{
@@ -331,11 +336,20 @@ static uint32_t compute_page_hash(void *ptr)
v2 = QEMU_XXHASH_SEED + XXH_PRIME64_2;
v3 = QEMU_XXHASH_SEED + 0;
v4 = QEMU_XXHASH_SEED - XXH_PRIME64_1;
- for (i = 0; i < TARGET_PAGE_SIZE / 8; i += 4) {
- v1 = XXH64_round(v1, p[i + 0]);
- v2 = XXH64_round(v2, p[i + 1]);
- v3 = XXH64_round(v3, p[i + 2]);
- v4 = XXH64_round(v4, p[i + 3]);
+ if (ptr) {
+ for (i = 0; i < TARGET_PAGE_SIZE / 8; i += 4) {
+ v1 = XXH64_round(v1, p[i + 0]);
+ v2 = XXH64_round(v2, p[i + 1]);
+ v3 = XXH64_round(v3, p[i + 2]);
+ v4 = XXH64_round(v4, p[i + 3]);
+ }
+ } else {
+ for (i = 0; i < TARGET_PAGE_SIZE / 8; i += 4) {
+ v1 = XXH64_round(v1, 0);
+ v2 = XXH64_round(v2, 0);
+ v3 = XXH64_round(v3, 0);
+ v4 = XXH64_round(v4, 0);
+ }
}
res = XXH64_mergerounds(v1, v2, v3, v4);
res += TARGET_PAGE_SIZE;
@@ -343,6 +357,17 @@ static uint32_t compute_page_hash(void *ptr)
return (uint32_t)(res & UINT32_MAX);
}
+static uint32_t get_zero_page_hash(void)
+{
+ static uint32_t hash;
+ static int is_computed;
+
+ if (!is_computed) {
+ hash = compute_page_hash(NULL);
+ is_computed = 1;
+ }
+ return hash;
+}
/*
* get hash result for the sampled memory with length of TARGET_PAGE_SIZE
@@ -364,6 +389,7 @@ static bool save_ramblock_hash(struct RamblockDirtyInfo
*info)
unsigned int sample_pages_count;
int i;
GRand *rand;
+ uint32_t zero_page_hash = get_zero_page_hash();
sample_pages_count = info->sample_pages_count;
@@ -393,6 +419,9 @@ static bool save_ramblock_hash(struct RamblockDirtyInfo
*info)
info->hash_result[i] = get_ramblock_vfn_hash(info,
info->sample_page_vfn[i]);
DirtyStat.page_sampling.n_sampled_pages++;
+ if (info->hash_result[i] == zero_page_hash) {
+ DirtyStat.page_sampling.n_zero_pages++;
+ }
}
g_rand_free(rand);
@@ -891,6 +920,7 @@ void hmp_info_dirty_rate(Monitor *mon, const QDict *qdict)
monitor_printf(mon, "Page count (page size %d):\n", TARGET_PAGE_SIZE);
monitor_printf(mon, " Total: %"PRIi64"\n", info->n_total_pages);
monitor_printf(mon, " Sampled: %"PRIi64"\n", info->n_sampled_pages);
+ monitor_printf(mon, " Zero: %"PRIi64"\n", info->n_zero_pages);
int64List *periods = info->periods;
int64List *n_dirty_pages = info->n_dirty_pages;
while (periods) {
diff --git a/migration/dirtyrate.h b/migration/dirtyrate.h
index 7a97e2b076..e2af72fb8c 100644
--- a/migration/dirtyrate.h
+++ b/migration/dirtyrate.h
@@ -80,6 +80,7 @@ typedef struct DirtyReading {
typedef struct SampleVMStat {
int64_t n_total_pages; /* total number of pages */
int64_t n_sampled_pages; /* number of sampled pages */
+ int64_t n_zero_pages; /* number of observed zero pages */
int64_t n_readings;
DirtyReading *readings;
} SampleVMStat;
diff --git a/qapi/migration.json b/qapi/migration.json
index f818f51e0e..2c48a9ef80 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -1811,6 +1811,9 @@
#
# @n-sampled-pages: [page-sampling] number of sampled VM pages (since 8.1)
#
+# @n-zero-pages: [page-sampling] number of observed all-zero pages among all
+# sampled pages (since 8.1)
+#
# @periods: [page-sampling] array of time periods expressed in milliseconds
# for which dirty-sample measurements were collected (since 8.1)
#
@@ -1834,6 +1837,7 @@
'page-size': 'int64',
'*n-total-pages': 'int64',
'*n-sampled-pages': 'int64',
+ '*n-zero-pages': 'int64',
'*periods': ['int64'],
'*n-dirty-pages': ['int64'] } }
--
2.30.2
