Re: [Qemu-devel] [PATCH RFC v3 13/27] COLO RAM: Flush cached RAM into SVM's memory

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* zhanghailiang (zhang.zhanghailiang@huawei.com) wrote:
> On 2015/3/12 4:07, Dr. David Alan Gilbert wrote:
> >* zhanghailiang (zhang.zhanghailiang@huawei.com) wrote:
> >>We only need to flush RAM that is both dirty on PVM and SVM since
> >>last checkpoint. Besides, we must ensure flush RAM cache before load
> >>device state.
> >
> >Actually with a follow up to my previous question, can you explain the 'both'
> >in that description.
> >
> 
> The description is wrong,
> It should be 'any page that dirtied by PVM or SVM'. Sorry for my poor english.

That's fine; thank you for the clarification.

Dave

> 
> >If a page was dirty on just the PVM, but not the SVM, you would have to copy
> >the new PVM page into the SVM ram before executing with the newly received device
> >state, otherwise the device state would be inconsistent with the RAM state.
> >
> >Dave
> >
> >>Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>a
> >>Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> >>Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
> >>Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
> >>Signed-off-by: Gonglei <arei.gonglei@huawei.com>
> >>---
> >>  arch_init.c                        | 91 +++++++++++++++++++++++++++++++++++++-
> >>  include/migration/migration-colo.h |  1 +
> >>  migration/colo.c                   |  1 -
> >>  3 files changed, 91 insertions(+), 2 deletions(-)
> >>
> >>diff --git a/arch_init.c b/arch_init.c
> >>index 4a1d825..f70de23 100644
> >>--- a/arch_init.c
> >>+++ b/arch_init.c
> >>@@ -1100,6 +1100,7 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
> >>  {
> >>      int flags = 0, ret = 0;
> >>      static uint64_t seq_iter;
> >>+    bool need_flush = false;
> >>
> >>      seq_iter++;
> >>
> >>@@ -1163,6 +1164,7 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
> >>                  break;
> >>              }
> >>
> >>+            need_flush = true;
> >>              ch = qemu_get_byte(f);
> >>              ram_handle_compressed(host, ch, TARGET_PAGE_SIZE);
> >>              break;
> >>@@ -1174,6 +1176,7 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
> >>                  break;
> >>              }
> >>
> >>+            need_flush = true;
> >>              qemu_get_buffer(f, host, TARGET_PAGE_SIZE);
> >>              break;
> >>          case RAM_SAVE_FLAG_XBZRLE:
> >>@@ -1190,6 +1193,7 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
> >>                  ret = -EINVAL;
> >>                  break;
> >>              }
> >>+            need_flush = true;
> >>              break;
> >>          case RAM_SAVE_FLAG_EOS:
> >>              /* normal exit */
> >>@@ -1207,7 +1211,10 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
> >>              ret = qemu_file_get_error(f);
> >>          }
> >>      }
> >>-
> >>+    if (!ret  && ram_cache_enable && need_flush) {
> >>+        DPRINTF("Flush ram_cache\n");
> >>+        colo_flush_ram_cache();
> >>+    }
> >>      DPRINTF("Completed load of VM with exit code %d seq iteration "
> >>              "%" PRIu64 "\n", ret, seq_iter);
> >>      return ret;
> >>@@ -1220,6 +1227,7 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
> >>  void create_and_init_ram_cache(void)
> >>  {
> >>      RAMBlock *block;
> >>+    int64_t ram_cache_pages = last_ram_offset() >> TARGET_PAGE_BITS;
> >>
> >>      QTAILQ_FOREACH(block, &ram_list.blocks, next) {
> >>          block->host_cache = g_malloc(block->used_length);
> >>@@ -1227,6 +1235,14 @@ void create_and_init_ram_cache(void)
> >>      }
> >>
> >>      ram_cache_enable = true;
> >>+    /*
> >>+    * Start dirty log for slave VM, we will use this dirty bitmap together with
> >>+    * VM's cache RAM dirty bitmap to decide which page in cache should be
> >>+    * flushed into VM's RAM.
> >>+    */
> >>+    migration_bitmap = bitmap_new(ram_cache_pages);
> >>+    migration_dirty_pages = 0;
> >>+    memory_global_dirty_log_start();
> >>  }
> >>
> >>  void release_ram_cache(void)
> >>@@ -1261,6 +1277,79 @@ static void *memory_region_get_ram_cache_ptr(MemoryRegion *mr, RAMBlock *block)
> >>      return block->host_cache + (addr - block->offset);
> >>  }
> >>
> >>+static inline
> >>+ram_addr_t host_bitmap_find_and_reset_dirty(MemoryRegion *mr,
> >>+                                            ram_addr_t start)
> >>+{
> >>+    unsigned long base = mr->ram_addr >> TARGET_PAGE_BITS;
> >>+    unsigned long nr = base + (start >> TARGET_PAGE_BITS);
> >>+    unsigned long size = base + (int128_get64(mr->size) >> TARGET_PAGE_BITS);
> >>+
> >>+    unsigned long next;
> >>+
> >>+    next = find_next_bit(ram_list.dirty_memory[DIRTY_MEMORY_MIGRATION],
> >>+                         size, nr);
> >>+    if (next < size) {
> >>+        clear_bit(next, ram_list.dirty_memory[DIRTY_MEMORY_MIGRATION]);
> >>+    }
> >>+    return (next - base) << TARGET_PAGE_BITS;
> >>+}
> >>+
> >>+void colo_flush_ram_cache(void)
> >>+{
> >>+    RAMBlock *block = NULL;
> >>+    void *dst_host;
> >>+    void *src_host;
> >>+    ram_addr_t ca  = 0, ha = 0;
> >>+    bool got_ca = 0, got_ha = 0;
> >>+    int64_t host_dirty = 0, both_dirty = 0;
> >>+
> >>+    address_space_sync_dirty_bitmap(&address_space_memory);
> >>+
> >>+    block = QTAILQ_FIRST(&ram_list.blocks);
> >>+    while (true) {
> >>+        if (ca < block->used_length && ca <= ha) {
> >>+            ca = migration_bitmap_find_and_reset_dirty(block->mr, ca);
> >>+            if (ca < block->used_length) {
> >>+                got_ca = 1;
> >>+            }
> >>+        }
> >>+        if (ha < block->used_length && ha <= ca) {
> >>+            ha = host_bitmap_find_and_reset_dirty(block->mr, ha);
> >>+            if (ha < block->used_length && ha != ca) {
> >>+                got_ha = 1;
> >>+            }
> >>+            host_dirty += (ha < block->used_length ? 1 : 0);
> >>+            both_dirty += (ha < block->used_length && ha == ca ? 1 : 0);
> >>+        }
> >>+        if (ca >= block->used_length && ha >= block->used_length) {
> >>+            ca = 0;
> >>+            ha = 0;
> >>+            block = QTAILQ_NEXT(block, next);
> >>+            if (!block) {
> >>+                break;
> >>+            }
> >>+        } else {
> >>+            if (got_ha) {
> >>+                got_ha = 0;
> >>+                dst_host = memory_region_get_ram_ptr(block->mr) + ha;
> >>+                src_host = memory_region_get_ram_cache_ptr(block->mr, block)
> >>+                           + ha;
> >>+                memcpy(dst_host, src_host, TARGET_PAGE_SIZE);
> >>+            }
> >>+            if (got_ca) {
> >>+                got_ca = 0;
> >>+                dst_host = memory_region_get_ram_ptr(block->mr) + ca;
> >>+                src_host = memory_region_get_ram_cache_ptr(block->mr, block)
> >>+                           + ca;
> >>+                memcpy(dst_host, src_host, TARGET_PAGE_SIZE);
> >>+            }
> >>+        }
> >>+    }
> >>+
> >>+    assert(migration_dirty_pages == 0);
> >>+}
> >>+
> >>  static SaveVMHandlers savevm_ram_handlers = {
> >>      .save_live_setup = ram_save_setup,
> >>      .save_live_iterate = ram_save_iterate,
> >>diff --git a/include/migration/migration-colo.h b/include/migration/migration-colo.h
> >>index 7d43aed..2084fe2 100644
> >>--- a/include/migration/migration-colo.h
> >>+++ b/include/migration/migration-colo.h
> >>@@ -36,5 +36,6 @@ void *colo_process_incoming_checkpoints(void *opaque);
> >>  bool loadvm_in_colo_state(void);
> >>  /* ram cache */
> >>  void create_and_init_ram_cache(void);
> >>+void colo_flush_ram_cache(void);
> >>  void release_ram_cache(void);
> >>  #endif
> >>diff --git a/migration/colo.c b/migration/colo.c
> >>index a0e1b7a..5ff2ee8 100644
> >>--- a/migration/colo.c
> >>+++ b/migration/colo.c
> >>@@ -397,7 +397,6 @@ void *colo_process_incoming_checkpoints(void *opaque)
> >>          }
> >>          DPRINTF("Finish load all vm state to cache\n");
> >>          qemu_mutex_unlock_iothread();
> >>-        /* TODO: flush vm state */
> >>
> >>          ret = colo_ctl_put(ctl, COLO_CHECKPOINT_LOADED);
> >>          if (ret < 0) {
> >>--
> >>1.7.12.4
> >>
> >>
> >--
> >Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
> >
> >.
> >
> 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK