diff options
author | Xiao Guangrong <xiaoguangrong@tencent.com> | 2018-09-03 17:26:42 +0800 |
---|---|---|
committer | Dr. David Alan Gilbert <dgilbert@redhat.com> | 2018-09-26 12:21:56 +0100 |
commit | be8b02edae9aa3a64c1e76cb4067b4bbbb170448 (patch) | |
tree | 4a8c346a9f6f86f69467285fa4b24fd8c8089278 | |
parent | 449f91b2c8d2ddf53629d908593f9acf52301b2d (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.c | 18 |
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. |