[Qemu-devel] [PULL 40/65] ram: Remove compression_switch and inline its logic

[Juan Quintela]

We can calculate its value, so we don't create a variable for it.

Signed-off-by: Juan Quintela <address@hidden>
Reviewed-by: Dr. David Alan Gilbert <address@hidden>

--

After Peter and Dave review, I dropped the variable and just inlined
the condition.

Fix typo
---
 migration/ram.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index 14d54fd..fa5a290 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -336,7 +336,6 @@ static QemuCond comp_done_cond;
 /* The empty QEMUFileOps will be used by file in CompressParam */
 static const QEMUFileOps empty_ops = { };
 
-static bool compression_switch;
 static DecompressParam *decomp_param;
 static QemuThread *decompress_threads;
 static QemuMutex decomp_done_lock;
@@ -420,7 +419,6 @@ void migrate_compress_threads_create(void)
     if (!migrate_use_compression()) {
         return;
     }
-    compression_switch = true;
     thread_count = migrate_compress_threads();
     compress_threads = g_new0(QemuThread, thread_count);
     comp_param = g_new0(CompressParam, thread_count);
@@ -1092,7 +1090,6 @@ static bool find_dirty_block(RAMState *rs, 
PageSearchStatus *pss,
                  * point. In theory, xbzrle can do better than compression.
                  */
                 flush_compressed_data(rs);
-                compression_switch = false;
             }
         }
         /* Didn't find anything this time, but try again on the new block */
@@ -1326,7 +1323,14 @@ static int ram_save_target_page(RAMState *rs, 
MigrationState *ms,
     /* Check the pages is dirty and if it is send it */
     if (migration_bitmap_clear_dirty(rs, dirty_ram_abs)) {
         unsigned long *unsentmap;
-        if (compression_switch && migrate_use_compression()) {
+        /*
+         * If xbzrle is on, stop using the data compression after first
+         * round of migration even if compression is enabled. In theory,
+         * xbzrle can do better than compression.
+         */
+
+        if (migrate_use_compression()
+            && (rs->ram_bulk_stage || !migrate_use_xbzrle())) {
             res = ram_save_compressed_page(rs, ms, pss, last_stage);
         } else {
             res = ram_save_page(rs, ms, pss, last_stage);
-- 
2.9.3