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authorXiao Guangrong <xiaoguangrong@tencent.com>2018-09-03 17:26:42 +0800
committerDr. David Alan Gilbert <dgilbert@redhat.com>2018-09-26 12:21:56 +0100
commitbe8b02edae9aa3a64c1e76cb4067b4bbbb170448 (patch)
tree4a8c346a9f6f86f69467285fa4b24fd8c8089278
parent449f91b2c8d2ddf53629d908593f9acf52301b2d (diff)
migration: fix calculating xbzrle_counters.cache_miss_rate
As Peter pointed out: | - xbzrle_counters.cache_miss is done in save_xbzrle_page(), so it's | per-guest-page granularity | | - RAMState.iterations is done for each ram_find_and_save_block(), so | it's per-host-page granularity | | An example is that when we migrate a 2M huge page in the guest, we | will only increase the RAMState.iterations by 1 (since | ram_find_and_save_block() will be called once), but we might increase | xbzrle_counters.cache_miss for 2M/4K=512 times (we'll call | save_xbzrle_page() that many times) if all the pages got cache miss. | Then IMHO the cache miss rate will be 512/1=51200% (while it should | actually be just 100% cache miss). And he also suggested as xbzrle_counters.cache_miss_rate is the only user of rs->iterations we can adapt it to count target guest page numbers After that, rename 'iterations' to 'target_page_count' to better reflect its meaning Suggested-by: Peter Xu <peterx@redhat.com> Reviewed-by: Peter Xu <peterx@redhat.com> Reviewed-by: Juan Quintela <quintela@redhat.com> Signed-off-by: Xiao Guangrong <xiaoguangrong@tencent.com> Message-Id: <20180903092644.25812-3-xiaoguangrong@tencent.com> Signed-off-by: Juan Quintela <quintela@redhat.com> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
-rw-r--r--migration/ram.c18
1 files changed, 9 insertions, 9 deletions
diff --git a/migration/ram.c b/migration/ram.c
index f6fd8e5e09..0423ef0f08 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -301,10 +301,10 @@ struct RAMState {
uint64_t num_dirty_pages_period;
/* xbzrle misses since the beginning of the period */
uint64_t xbzrle_cache_miss_prev;
- /* number of iterations at the beginning of period */
- uint64_t iterations_prev;
- /* Iterations since start */
- uint64_t iterations;
+ /* total handled target pages at the beginning of period */
+ uint64_t target_page_count_prev;
+ /* total handled target pages since start */
+ uint64_t target_page_count;
/* number of dirty bits in the bitmap */
uint64_t migration_dirty_pages;
/* protects modification of the bitmap */
@@ -1592,19 +1592,19 @@ uint64_t ram_pagesize_summary(void)
static void migration_update_rates(RAMState *rs, int64_t end_time)
{
- uint64_t iter_count = rs->iterations - rs->iterations_prev;
+ uint64_t page_count = rs->target_page_count - rs->target_page_count_prev;
/* calculate period counters */
ram_counters.dirty_pages_rate = rs->num_dirty_pages_period * 1000
/ (end_time - rs->time_last_bitmap_sync);
- if (!iter_count) {
+ if (!page_count) {
return;
}
if (migrate_use_xbzrle()) {
xbzrle_counters.cache_miss_rate = (double)(xbzrle_counters.cache_miss -
- rs->xbzrle_cache_miss_prev) / iter_count;
+ rs->xbzrle_cache_miss_prev) / page_count;
rs->xbzrle_cache_miss_prev = xbzrle_counters.cache_miss;
}
}
@@ -1662,7 +1662,7 @@ static void migration_bitmap_sync(RAMState *rs)
migration_update_rates(rs, end_time);
- rs->iterations_prev = rs->iterations;
+ rs->target_page_count_prev = rs->target_page_count;
/* reset period counters */
rs->time_last_bitmap_sync = end_time;
@@ -3196,7 +3196,7 @@ static int ram_save_iterate(QEMUFile *f, void *opaque)
done = 1;
break;
}
- rs->iterations++;
+ rs->target_page_count += pages;
/* we want to check in the 1st loop, just in case it was the 1st time
and we had to sync the dirty bitmap.