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[Qemu-devel] [PULL 34/57] Postcopy: Maintain unsentmap
From: |
Juan Quintela |
Subject: |
[Qemu-devel] [PULL 34/57] Postcopy: Maintain unsentmap |
Date: |
Mon, 9 Nov 2015 18:28:38 +0100 |
From: "Dr. David Alan Gilbert" <address@hidden>
Maintain an 'unsentmap' of pages that have yet to be sent.
This is used in the following patches to discard some set of
the pages already sent as we enter postcopy mode.
Signed-off-by: Dr. David Alan Gilbert <address@hidden>
Reviewed-by: Juan Quintela <address@hidden>
Signed-off-by: Juan Quintela <address@hidden>
---
migration/ram.c | 51 +++++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 45 insertions(+), 6 deletions(-)
diff --git a/migration/ram.c b/migration/ram.c
index 4053ca1..c703176 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -237,7 +237,14 @@ typedef struct PageSearchStatus PageSearchStatus;
static struct BitmapRcu {
struct rcu_head rcu;
+ /* Main migration bitmap */
unsigned long *bmap;
+ /* bitmap of pages that haven't been sent even once
+ * only maintained and used in postcopy at the moment
+ * where it's used to send the dirtymap at the start
+ * of the postcopy phase
+ */
+ unsigned long *unsentmap;
} *migration_bitmap_rcu;
struct CompressParam {
@@ -531,10 +538,18 @@ static int save_xbzrle_page(QEMUFile *f, uint8_t
**current_data,
return 1;
}
-/* Called with rcu_read_lock() to protect migration_bitmap */
+/* Called with rcu_read_lock() to protect migration_bitmap
+ * rb: The RAMBlock to search for dirty pages in
+ * start: Start address (typically so we can continue from previous page)
+ * ram_addr_abs: Pointer into which to store the address of the dirty page
+ * within the global ram_addr space
+ *
+ * Returns: byte offset within memory region of the start of a dirty page
+ */
static inline
ram_addr_t migration_bitmap_find_and_reset_dirty(RAMBlock *rb,
- ram_addr_t start)
+ ram_addr_t start,
+ ram_addr_t *ram_addr_abs)
{
unsigned long base = rb->offset >> TARGET_PAGE_BITS;
unsigned long nr = base + (start >> TARGET_PAGE_BITS);
@@ -555,6 +570,7 @@ ram_addr_t migration_bitmap_find_and_reset_dirty(RAMBlock
*rb,
clear_bit(next, bitmap);
migration_dirty_pages--;
}
+ *ram_addr_abs = next << TARGET_PAGE_BITS;
return (next - base) << TARGET_PAGE_BITS;
}
@@ -953,10 +969,11 @@ static int ram_save_compressed_page(QEMUFile *f, RAMBlock
*block,
* @*again: Set to false if the search has scanned the whole of RAM
*/
static bool find_dirty_block(QEMUFile *f, PageSearchStatus *pss,
- bool *again)
+ bool *again, ram_addr_t *ram_addr_abs)
{
pss->offset = migration_bitmap_find_and_reset_dirty(pss->block,
- pss->offset);
+ pss->offset,
+ ram_addr_abs);
if (pss->complete_round && pss->block == last_seen_block &&
pss->offset >= last_offset) {
/*
@@ -1014,6 +1031,8 @@ static int ram_find_and_save_block(QEMUFile *f, bool
last_stage,
PageSearchStatus pss;
int pages = 0;
bool again, found;
+ ram_addr_t dirty_ram_abs; /* Address of the start of the dirty page in
+ ram_addr_t space */
pss.block = last_seen_block;
pss.offset = last_offset;
@@ -1024,7 +1043,7 @@ static int ram_find_and_save_block(QEMUFile *f, bool
last_stage,
}
do {
- found = find_dirty_block(f, &pss, &again);
+ found = find_dirty_block(f, &pss, &again, &dirty_ram_abs);
if (found) {
if (compression_switch && migrate_use_compression()) {
@@ -1038,7 +1057,14 @@ static int ram_find_and_save_block(QEMUFile *f, bool
last_stage,
/* if page is unmodified, continue to the next */
if (pages > 0) {
+ unsigned long *unsentmap;
+
+ unsentmap = atomic_rcu_read(&migration_bitmap_rcu)->unsentmap;
last_sent_block = pss.block;
+ if (unsentmap) {
+ clear_bit(dirty_ram_abs >> TARGET_PAGE_BITS, unsentmap);
+ }
+
}
}
} while (!pages && again);
@@ -1097,6 +1123,7 @@ void free_xbzrle_decoded_buf(void)
static void migration_bitmap_free(struct BitmapRcu *bmap)
{
g_free(bmap->bmap);
+ g_free(bmap->unsentmap);
g_free(bmap);
}
@@ -1153,6 +1180,13 @@ void migration_bitmap_extend(ram_addr_t old, ram_addr_t
new)
qemu_mutex_lock(&migration_bitmap_mutex);
bitmap_copy(bitmap->bmap, old_bitmap->bmap, old);
bitmap_set(bitmap->bmap, old, new - old);
+
+ /* We don't have a way to safely extend the sentmap
+ * with RCU; so mark it as missing, entry to postcopy
+ * will fail.
+ */
+ bitmap->unsentmap = NULL;
+
atomic_rcu_set(&migration_bitmap_rcu, bitmap);
qemu_mutex_unlock(&migration_bitmap_mutex);
migration_dirty_pages += new - old;
@@ -1253,10 +1287,15 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
reset_ram_globals();
ram_bitmap_pages = last_ram_offset() >> TARGET_PAGE_BITS;
- migration_bitmap_rcu = g_new(struct BitmapRcu, 1);
+ migration_bitmap_rcu = g_new0(struct BitmapRcu, 1);
migration_bitmap_rcu->bmap = bitmap_new(ram_bitmap_pages);
bitmap_set(migration_bitmap_rcu->bmap, 0, ram_bitmap_pages);
+ if (migrate_postcopy_ram()) {
+ migration_bitmap_rcu->unsentmap = bitmap_new(ram_bitmap_pages);
+ bitmap_set(migration_bitmap_rcu->unsentmap, 0, ram_bitmap_pages);
+ }
+
/*
* Count the total number of pages used by ram blocks not including any
* gaps due to alignment or unplugs.
--
2.5.0
- [Qemu-devel] [PULL 28/57] postcopy: OS support test, (continued)
- [Qemu-devel] [PULL 33/57] Add qemu_savevm_state_complete_postcopy, Juan Quintela, 2015/11/09
- [Qemu-devel] [PULL 35/57] migration_completion: Take current state, Juan Quintela, 2015/11/09
- [Qemu-devel] [PULL 36/57] postcopy: Incoming initialisation, Juan Quintela, 2015/11/09
- [Qemu-devel] [PULL 34/57] Postcopy: Maintain unsentmap,
Juan Quintela <=
- [Qemu-devel] [PULL 38/57] Postcopy: Postcopy startup in migration thread, Juan Quintela, 2015/11/09
- [Qemu-devel] [PULL 37/57] postcopy: ram_enable_notify to switch on userfault, Juan Quintela, 2015/11/09
- [Qemu-devel] [PULL 39/57] Postcopy: End of iteration, Juan Quintela, 2015/11/09
- [Qemu-devel] [PULL 40/57] Page request: Add MIG_RP_MSG_REQ_PAGES reverse command, Juan Quintela, 2015/11/09
- [Qemu-devel] [PULL 42/57] Page request: Consume pages off the post-copy queue, Juan Quintela, 2015/11/09
- [Qemu-devel] [PULL 46/57] Don't sync dirty bitmaps in postcopy, Juan Quintela, 2015/11/09
- [Qemu-devel] [PULL 44/57] Postcopy: Use helpers to map pages during migration, Juan Quintela, 2015/11/09
- [Qemu-devel] [PULL 43/57] postcopy_ram.c: place_page and helpers, Juan Quintela, 2015/11/09
- [Qemu-devel] [PULL 49/57] Round up RAMBlock sizes to host page sizes, Juan Quintela, 2015/11/09
- [Qemu-devel] [PULL 41/57] Page request: Process incoming page request, Juan Quintela, 2015/11/09