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Re: [Qemu-devel] [PATCH 15/15] COLO: flush host dirty ram from cache

From: Hailiang Zhang
Subject: Re: [Qemu-devel] [PATCH 15/15] COLO: flush host dirty ram from cache
Date: Mon, 10 Apr 2017 15:13:58 +0800
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1

On 2017/4/8 1:39, Dr. David Alan Gilbert wrote:
* zhanghailiang (address@hidden) wrote:
Don't need to flush all VM's ram from cache, only
flush the dirty pages since last checkpoint

Cc: Juan Quintela <address@hidden>
Signed-off-by: Li Zhijian <address@hidden>
Signed-off-by: Zhang Chen <address@hidden>
Signed-off-by: zhanghailiang <address@hidden>
  migration/ram.c | 10 ++++++++++
  1 file changed, 10 insertions(+)

diff --git a/migration/ram.c b/migration/ram.c
index 6227b94..e9ba740 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2702,6 +2702,7 @@ int colo_init_ram_cache(void)
      migration_bitmap_rcu = g_new0(struct BitmapRcu, 1);
      migration_bitmap_rcu->bmap = bitmap_new(ram_cache_pages);
      migration_dirty_pages = 0;
+    memory_global_dirty_log_start();
Shouldn't there be a stop somewhere?
(Probably if you failover to the secondary and colo stops?)

Ha, good catch, i forgot to stop the dirty log in secondary side.

      return 0;
@@ -2750,6 +2751,15 @@ void colo_flush_ram_cache(void)
      void *src_host;
      ram_addr_t offset = 0;
+ memory_global_dirty_log_sync();
+    qemu_mutex_lock(&migration_bitmap_mutex);
+    rcu_read_lock();
+    QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
+        migration_bitmap_sync_range(block->offset, block->used_length);
+    }
+    rcu_read_unlock();
+    qemu_mutex_unlock(&migration_bitmap_mutex);
Again this might have some fun merging with Juan's recent changes - what's
really unusual about your set is that you're using this bitmap on the 
I suspect Juan's recent changes that trickier.
Check 'Creating RAMState for migration' and 'Split migration bitmaps by 

I have reviewed these two series, and i think it's not a big problem
for COLO here,  We can still re-use most of the codes.


      block = QLIST_FIRST_RCU(&ram_list.blocks);

Dr. David Alan Gilbert / address@hidden / Manchester, UK


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