[PATCH RFC 12/13] migration: Move last_sent_block into PageSearchStatus

[Peter Xu <peterx@redhat.com>]

Since we use PageSearchStatus to represent a channel, it makes perfect
sense to keep last_sent_block (aka, leverage RAM_SAVE_FLAG_CONTINUE) to be
per-channel rather than global because each channel can be sending
different pages on ramblocks.

Hence move it from RAMState into PageSearchStatus.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 migration/ram.c | 71 ++++++++++++++++++++++++++++---------------------
 1 file changed, 41 insertions(+), 30 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index 2be9b91ffc..ef89812c69 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -89,6 +89,8 @@ XBZRLECacheStats xbzrle_counters;
 struct PageSearchStatus {
     /* The migration channel used for a specific host page */
     QEMUFile    *pss_channel;
+    /* Last block from where we have sent data */
+    RAMBlock *last_sent_block;
     /* Current block being searched */
     RAMBlock    *block;
     /* Current page to search from */
@@ -368,8 +370,6 @@ struct RAMState {
     int uffdio_fd;
     /* Last block that we have visited searching for dirty pages */
     RAMBlock *last_seen_block;
-    /* Last block from where we have sent data */
-    RAMBlock *last_sent_block;
     /* Last dirty target page we have sent */
     ram_addr_t last_page;
     /* last ram version we have seen */
@@ -677,16 +677,17 @@ exit:
  *
  * Returns the number of bytes written
  *
- * @f: QEMUFile where to send the data
+ * @pss: current PSS channel status
  * @block: block that contains the page we want to send
  * @offset: offset inside the block for the page
  *          in the lower bits, it contains flags
  */
-static size_t save_page_header(RAMState *rs, QEMUFile *f,  RAMBlock *block,
+static size_t save_page_header(PageSearchStatus *pss, RAMBlock *block,
                                ram_addr_t offset)
 {
     size_t size, len;
-    bool same_block = (block == rs->last_sent_block);
+    bool same_block = (block == pss->last_sent_block);
+    QEMUFile *f = pss->pss_channel;
 
     if (same_block) {
         offset |= RAM_SAVE_FLAG_CONTINUE;
@@ -699,7 +700,7 @@ static size_t save_page_header(RAMState *rs, QEMUFile *f,  RAMBlock *block,
         qemu_put_byte(f, len);
         qemu_put_buffer(f, (uint8_t *)block->idstr, len);
         size += 1 + len;
-        rs->last_sent_block = block;
+        pss->last_sent_block = block;
     }
     return size;
 }
@@ -783,17 +784,19 @@ static void xbzrle_cache_zero_page(RAMState *rs, ram_addr_t current_addr)
  *          -1 means that xbzrle would be longer than normal
  *
  * @rs: current RAM state
+ * @pss: current PSS channel
  * @current_data: pointer to the address of the page contents
  * @current_addr: addr of the page
  * @block: block that contains the page we want to send
  * @offset: offset inside the block for the page
  */
-static int save_xbzrle_page(RAMState *rs, QEMUFile *file,
+static int save_xbzrle_page(RAMState *rs, PageSearchStatus *pss,
                             uint8_t **current_data, ram_addr_t current_addr,
                             RAMBlock *block, ram_addr_t offset)
 {
     int encoded_len = 0, bytes_xbzrle;
     uint8_t *prev_cached_page;
+    QEMUFile *file = pss->pss_channel;
 
     if (!cache_is_cached(XBZRLE.cache, current_addr,
                          ram_counters.dirty_sync_count)) {
@@ -858,7 +861,7 @@ static int save_xbzrle_page(RAMState *rs, QEMUFile *file,
     }
 
     /* Send XBZRLE based compressed page */
-    bytes_xbzrle = save_page_header(rs, file, block,
+    bytes_xbzrle = save_page_header(pss, block,
                                     offset | RAM_SAVE_FLAG_XBZRLE);
     qemu_put_byte(file, ENCODING_FLAG_XBZRLE);
     qemu_put_be16(file, encoded_len);
@@ -1286,19 +1289,19 @@ static void ram_release_page(const char *rbname, uint64_t offset)
  * Returns the size of data written to the file, 0 means the page is not
  * a zero page
  *
- * @rs: current RAM state
- * @file: the file where the data is saved
+ * @pss: current PSS channel
  * @block: block that contains the page we want to send
  * @offset: offset inside the block for the page
  */
-static int save_zero_page_to_file(RAMState *rs, QEMUFile *file,
+static int save_zero_page_to_file(PageSearchStatus *pss,
                                   RAMBlock *block, ram_addr_t offset)
 {
     uint8_t *p = block->host + offset;
+    QEMUFile *file = pss->pss_channel;
     int len = 0;
 
     if (buffer_is_zero(p, TARGET_PAGE_SIZE)) {
-        len += save_page_header(rs, file, block, offset | RAM_SAVE_FLAG_ZERO);
+        len += save_page_header(pss, block, offset | RAM_SAVE_FLAG_ZERO);
         qemu_put_byte(file, 0);
         len += 1;
         ram_release_page(block->idstr, offset);
@@ -1311,14 +1314,14 @@ static int save_zero_page_to_file(RAMState *rs, QEMUFile *file,
  *
  * Returns the number of pages written.
  *
- * @rs: current RAM state
+ * @pss: current PSS channel
  * @block: block that contains the page we want to send
  * @offset: offset inside the block for the page
  */
-static int save_zero_page(RAMState *rs, QEMUFile *file, RAMBlock *block,
+static int save_zero_page(PageSearchStatus *pss, RAMBlock *block,
                           ram_addr_t offset)
 {
-    int len = save_zero_page_to_file(rs, file, block, offset);
+    int len = save_zero_page_to_file(pss, block, offset);
 
     if (len) {
         ram_counters.duplicate++;
@@ -1371,16 +1374,18 @@ static bool control_save_page(PageSearchStatus *pss, RAMBlock *block,
  *
  * Returns the number of pages written.
  *
- * @rs: current RAM state
+ * @pss: current PSS channel
  * @block: block that contains the page we want to send
  * @offset: offset inside the block for the page
  * @buf: the page to be sent
  * @async: send to page asyncly
  */
-static int save_normal_page(RAMState *rs, QEMUFile *file, RAMBlock *block,
+static int save_normal_page(PageSearchStatus *pss, RAMBlock *block,
                             ram_addr_t offset, uint8_t *buf, bool async)
 {
-    ram_transferred_add(save_page_header(rs, file, block,
+    QEMUFile *file = pss->pss_channel;
+
+    ram_transferred_add(save_page_header(pss, block,
                                          offset | RAM_SAVE_FLAG_PAGE));
     if (async) {
         qemu_put_buffer_async(file, buf, TARGET_PAGE_SIZE,
@@ -1420,7 +1425,7 @@ static int ram_save_page(RAMState *rs, PageSearchStatus *pss)
 
     XBZRLE_cache_lock();
     if (rs->xbzrle_enabled && !migration_in_postcopy()) {
-        pages = save_xbzrle_page(rs, pss->pss_channel, &p, current_addr,
+        pages = save_xbzrle_page(rs, pss, &p, current_addr,
                                  block, offset);
         if (!rs->last_stage) {
             /* Can't send this cached data async, since the cache page
@@ -1432,8 +1437,7 @@ static int ram_save_page(RAMState *rs, PageSearchStatus *pss)
 
     /* XBZRLE overflow or normal page */
     if (pages == -1) {
-        pages = save_normal_page(rs, pss->pss_channel, block, offset,
-                                 p, send_async);
+        pages = save_normal_page(pss, block, offset, p, send_async);
     }
 
     XBZRLE_cache_unlock();
@@ -1456,14 +1460,15 @@ static bool do_compress_ram_page(QEMUFile *f, z_stream *stream, RAMBlock *block,
                                  ram_addr_t offset, uint8_t *source_buf)
 {
     RAMState *rs = ram_state;
+    PageSearchStatus *pss = &rs->pss[RAM_CHANNEL_PRECOPY];
     uint8_t *p = block->host + offset;
     int ret;
 
-    if (save_zero_page_to_file(rs, f, block, offset)) {
+    if (save_zero_page_to_file(pss, block, offset)) {
         return true;
     }
 
-    save_page_header(rs, f, block, offset | RAM_SAVE_FLAG_COMPRESS_PAGE);
+    save_page_header(pss, block, offset | RAM_SAVE_FLAG_COMPRESS_PAGE);
 
     /*
      * copy it to a internal buffer to avoid it being modified by VM
@@ -2283,7 +2288,8 @@ static bool save_page_use_compression(RAMState *rs)
  * has been properly handled by compression, otherwise needs other
  * paths to handle it
  */
-static bool save_compress_page(RAMState *rs, RAMBlock *block, ram_addr_t offset)
+static bool save_compress_page(RAMState *rs, PageSearchStatus *pss,
+                               RAMBlock *block, ram_addr_t offset)
 {
     if (!save_page_use_compression(rs)) {
         return false;
@@ -2299,7 +2305,7 @@ static bool save_compress_page(RAMState *rs, RAMBlock *block, ram_addr_t offset)
      * We post the fist page as normal page as compression will take
      * much CPU resource.
      */
-    if (block != rs->last_sent_block) {
+    if (block != pss->last_sent_block) {
         flush_compressed_data(rs);
         return false;
     }
@@ -2330,11 +2336,11 @@ static int ram_save_target_page(RAMState *rs, PageSearchStatus *pss)
         return res;
     }
 
-    if (save_compress_page(rs, block, offset)) {
+    if (save_compress_page(rs, pss, block, offset)) {
         return 1;
     }
 
-    res = save_zero_page(rs, pss->pss_channel, block, offset);
+    res = save_zero_page(pss, block, offset);
     if (res > 0) {
         /* Must let xbzrle know, otherwise a previous (now 0'd) cached
          * page would be stale
@@ -2466,7 +2472,7 @@ static void postcopy_preempt_choose_channel(RAMState *rs, PageSearchStatus *pss)
          * If channel switched, reset last_sent_block since the old sent block
          * may not be on the same channel.
          */
-        rs->last_sent_block = NULL;
+        pss->last_sent_block = NULL;
 
         trace_postcopy_preempt_switch_channel(channel);
     }
@@ -2793,8 +2799,13 @@ static void ram_save_cleanup(void *opaque)
 
 static void ram_state_reset(RAMState *rs)
 {
+    int i;
+
+    for (i = 0; i < RAM_CHANNEL_MAX; i++) {
+        rs->pss[i].last_sent_block = NULL;
+    }
+
     rs->last_seen_block = NULL;
-    rs->last_sent_block = NULL;
     rs->last_page = 0;
     rs->last_version = ram_list.version;
     rs->xbzrle_enabled = false;
@@ -2988,8 +2999,8 @@ void ram_postcopy_send_discard_bitmap(MigrationState *ms)
     migration_bitmap_sync(rs);
 
     /* Easiest way to make sure we don't resume in the middle of a host-page */
+    rs->pss[RAM_CHANNEL_PRECOPY].last_sent_block = NULL;
     rs->last_seen_block = NULL;
-    rs->last_sent_block = NULL;
     rs->last_page = 0;
 
     postcopy_each_ram_send_discard(ms);
-- 
2.32.0