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From: Paolo Bonzini <pbonzini@redhat.com>
To: qemu-devel@nongnu.org
Subject: [Qemu-devel] [PATCH 22/22] migration: run bitmap sync outside iothread lock
Date: Thu, 26 Mar 2015 18:38:40 +0100	[thread overview]
Message-ID: <1427391520-29497-23-git-send-email-pbonzini@redhat.com> (raw)
In-Reply-To: <1427391520-29497-1-git-send-email-pbonzini@redhat.com>

Synchronization of the dirty bitmap can now run concurrently
with modifications of it.

Note that the change in migration_bitmap_sync is not needed
and is only for improved clarity.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch_init.c           | 10 +++++-----
 include/exec/memory.h |  8 ++++++++
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch_init.c b/arch_init.c
index 75bba49..3ac63c6 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -512,10 +512,10 @@ static void migration_bitmap_sync(void)
         start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
     }
 
+    rcu_read_lock();
     trace_migration_bitmap_sync_start();
     address_space_sync_dirty_bitmap(&address_space_memory);
 
-    rcu_read_lock();
     QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
         migration_bitmap_sync_range(block->mr->ram_addr, block->used_length);
     }
@@ -838,7 +838,9 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
         acct_clear();
     }
 
-    /* iothread lock needed for ram_list.dirty_memory[] */
+    /* iothread lock needed for ram_list.dirty_memory[],
+     * ramlist lock needed for memory_global_dirty_log_start().
+     */
     qemu_mutex_lock_iothread();
     qemu_mutex_lock_ramlist();
     rcu_read_lock();
@@ -856,10 +858,10 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
     migration_dirty_pages = ram_bytes_total() >> TARGET_PAGE_BITS;
 
     memory_global_dirty_log_start();
-    migration_bitmap_sync();
     qemu_mutex_unlock_ramlist();
     qemu_mutex_unlock_iothread();
 
+    migration_bitmap_sync();
     qemu_put_be64(f, ram_bytes_total() | RAM_SAVE_FLAG_MEM_SIZE);
 
     QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
@@ -980,11 +982,9 @@ static uint64_t ram_save_pending(QEMUFile *f, void *opaque, uint64_t max_size)
     remaining_size = ram_save_remaining() * TARGET_PAGE_SIZE;
 
     if (remaining_size < max_size) {
-        qemu_mutex_lock_iothread();
         rcu_read_lock();
         migration_bitmap_sync();
         rcu_read_unlock();
-        qemu_mutex_unlock_iothread();
         remaining_size = ram_save_remaining() * TARGET_PAGE_SIZE;
     }
     return remaining_size;
diff --git a/include/exec/memory.h b/include/exec/memory.h
index aa46a52..e79e2d5 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -177,6 +177,9 @@ struct MemoryRegion {
  *
  * Allows a component to adjust to changes in the guest-visible memory map.
  * Use with memory_listener_register() and memory_listener_unregister().
+ *
+ * All functions called while holding the iothread lock, EXCEPT FOR log_sync
+ * which may be called either with or without the iothread lock held.
  */
 struct MemoryListener {
     void (*begin)(MemoryListener *listener);
@@ -682,6 +685,9 @@ bool memory_region_test_and_clear_dirty(MemoryRegion *mr, hwaddr addr,
  * Flushes dirty information from accelerators such as kvm and vhost-net
  * and makes it available to users of the memory API.
  *
+ * Unlike other memory region function, memory_region_sync_dirty_bitmap
+ * may be called either with or without the iothread lock held.
+ *
  * @mr: the region being flushed.
  */
 void memory_region_sync_dirty_bitmap(MemoryRegion *mr);
@@ -994,6 +1000,8 @@ MemoryRegionSection memory_region_find(MemoryRegion *mr,
  * address_space_sync_dirty_bitmap: synchronize the dirty log for all memory
  *
  * Synchronizes the dirty page log for an entire address space.
+ * May be called either with or without the iothread lock held.
+ *
  * @as: the address space that contains the memory being synchronized
  */
 void address_space_sync_dirty_bitmap(AddressSpace *as);
-- 
2.3.3

  parent reply	other threads:[~2015-03-26 17:39 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-26 17:38 [Qemu-devel] [PATCH 00/22] Dirty bitmap atomic access and optimizations Paolo Bonzini
2015-03-26 17:38 ` [Qemu-devel] [PATCH 01/22] memory: add memory_region_ram_resize Paolo Bonzini
2015-03-28 18:58   ` Michael S. Tsirkin
2015-03-29  7:30     ` Paolo Bonzini
2015-03-26 17:38 ` [Qemu-devel] [PATCH 02/22] acpi-build: remove dependency from ram_addr.h Paolo Bonzini
2015-03-28 18:58   ` Michael S. Tsirkin
2015-03-26 17:38 ` [Qemu-devel] [PATCH 03/22] memory: the only dirty memory flag for users is DIRTY_MEMORY_VGA Paolo Bonzini
2015-03-26 17:38 ` [Qemu-devel] [PATCH 04/22] display: enable DIRTY_MEMORY_VGA tracking explicitly Paolo Bonzini
2015-04-20 13:11   ` Stefan Hajnoczi
2015-04-20 13:54     ` Paolo Bonzini
2015-04-22  9:12       ` Stefan Hajnoczi
2015-03-26 17:38 ` [Qemu-devel] [PATCH 05/22] memory: return bitmap from memory_region_is_logging Paolo Bonzini
2015-03-27  5:44   ` Fam Zheng
2015-03-27  6:01     ` Paolo Bonzini
2015-03-28 18:54   ` Michael S. Tsirkin
2015-03-29  7:33     ` Paolo Bonzini
2015-03-26 17:38 ` [Qemu-devel] [PATCH 06/22] framebuffer: check memory_region_is_logging Paolo Bonzini
2015-03-26 17:38 ` [Qemu-devel] [PATCH 07/22] ui/console: " Paolo Bonzini
2015-03-26 17:38 ` [Qemu-devel] [PATCH 08/22] memory: track DIRTY_MEMORY_CODE in mr->dirty_log_mask Paolo Bonzini
2015-03-26 17:38 ` [Qemu-devel] [PATCH 09/22] memory: return DIRTY_MEMORY_MIGRATION from memory_region_is_logging Paolo Bonzini
2015-03-26 17:38 ` [Qemu-devel] [PATCH 10/22] ram_addr: tweaks to xen_modified_memory Paolo Bonzini
2015-03-28 19:04   ` Stefano Stabellini
2015-03-26 17:38 ` [Qemu-devel] [PATCH 11/22] exec: simplify notdirty_mem_write Paolo Bonzini
2015-03-26 17:38 ` [Qemu-devel] [PATCH 12/22] exec: use memory_region_is_logging to optimize dirty tracking Paolo Bonzini
2015-03-26 17:38 ` [Qemu-devel] [PATCH 13/22] exec: pass client mask to cpu_physical_memory_set_dirty_range Paolo Bonzini
2015-03-26 17:38 ` [Qemu-devel] [PATCH 14/22] exec: only check relevant bitmaps for cleanliness Paolo Bonzini
2015-03-27  6:10   ` Fam Zheng
2015-03-27  9:19     ` Paolo Bonzini
2015-03-26 17:38 ` [Qemu-devel] [PATCH 15/22] memory: do not touch code dirty bitmap unless TCG is enabled Paolo Bonzini
2015-03-26 17:38 ` [Qemu-devel] [PATCH 16/22] bitmap: add atomic set functions Paolo Bonzini
2015-03-26 17:38 ` [Qemu-devel] [PATCH 17/22] bitmap: add atomic test and clear Paolo Bonzini
2015-03-27  6:37   ` Fam Zheng
2015-03-27  9:21     ` Paolo Bonzini
2015-03-26 17:38 ` [Qemu-devel] [PATCH 18/22] memory: use atomic ops for setting dirty memory bits Paolo Bonzini
2015-03-26 17:38 ` [Qemu-devel] [PATCH 19/22] migration: move dirty bitmap sync to ram_addr.h Paolo Bonzini
2015-03-26 17:38 ` [Qemu-devel] [PATCH 20/22] memory: replace cpu_physical_memory_reset_dirty() with test-and-clear Paolo Bonzini
2015-03-26 17:38 ` [Qemu-devel] [PATCH 21/22] memory: make cpu_physical_memory_sync_dirty_bitmap() fully atomic Paolo Bonzini
2015-03-26 17:38 ` Paolo Bonzini [this message]
2015-04-20 13:23 ` [Qemu-devel] [PATCH 00/22] Dirty bitmap atomic access and optimizations Stefan Hajnoczi

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