diff options
| author | Stefan Hajnoczi <stefanha@redhat.com> | 2016-01-25 13:33:20 +0000 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2016-02-09 15:45:26 +0100 |
| commit | 5b82b703b69acc67b78b98a5efc897a3912719eb (patch) | |
| tree | f0532356113606ee7c64560e69149e865852a43c /migration | |
| parent | 8bafcb21643a39a5b29109f8bd5ee5a6f0f6850b (diff) | |
| download | qemu-5b82b703b69acc67b78b98a5efc897a3912719eb.tar.gz | |
memory: RCU ram_list.dirty_memory[] for safe RAM hotplug
Although accesses to ram_list.dirty_memory[] use atomics so multiple
threads can safely dirty the bitmap, the data structure is not fully
thread-safe yet.
This patch handles the RAM hotplug case where ram_list.dirty_memory[] is
grown. ram_list.dirty_memory[] is change from a regular bitmap to an
RCU array of pointers to fixed-size bitmap blocks. Threads can continue
accessing bitmap blocks while the array is being extended. See the
comments in the code for an in-depth explanation of struct
DirtyMemoryBlocks.
I have tested that live migration with virtio-blk dataplane works.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <1453728801-5398-2-git-send-email-stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'migration')
| -rw-r--r-- | migration/ram.c | 4 |
1 files changed, 0 insertions, 4 deletions
diff --git a/migration/ram.c b/migration/ram.c index 3cdfea4a5c..96c749face 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -609,7 +609,6 @@ static void migration_bitmap_sync_init(void) iterations_prev = 0; } -/* Called with iothread lock held, to protect ram_list.dirty_memory[] */ static void migration_bitmap_sync(void) { RAMBlock *block; @@ -1921,8 +1920,6 @@ static int ram_save_setup(QEMUFile *f, void *opaque) acct_clear(); } - /* iothread lock needed for ram_list.dirty_memory[] */ - qemu_mutex_lock_iothread(); qemu_mutex_lock_ramlist(); rcu_read_lock(); bytes_transferred = 0; @@ -1947,7 +1944,6 @@ static int ram_save_setup(QEMUFile *f, void *opaque) memory_global_dirty_log_start(); migration_bitmap_sync(); qemu_mutex_unlock_ramlist(); - qemu_mutex_unlock_iothread(); qemu_put_be64(f, ram_bytes_total() | RAM_SAVE_FLAG_MEM_SIZE); |