[PATCH 8/8] migration/multifd: cache channel count in multifd_send_sync_main

[Bin Guo <guobin@linux.alibaba.com>]

multifd_send_sync_main() is called once per RAM synchronization round
during live migration.  It iterates over all multifd channels twice
(signal loop + wait loop), calling migrate_multifd_channels()
independently in each loop header.

Cache migrate_multifd_channels() in a local thread_count variable at
function entry, matching the pattern already used in
multifd_send_setup() and multifd_recv_setup().  This eliminates 2
redundant config lookups per sync call.

Signed-off-by: Bin Guo <guobin@linux.alibaba.com>
---
 migration/multifd.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/migration/multifd.c b/migration/multifd.c
index cc2fa90204..bc8aacd660 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -611,13 +611,15 @@ static int multifd_zero_copy_flush(QIOChannel *c)
 int multifd_send_sync_main(MultiFDSyncReq req)
 {
     int i;
+    int thread_count;
     bool flush_zero_copy;
 
     assert(req != MULTIFD_SYNC_NONE);
 
+    thread_count = migrate_multifd_channels();
     flush_zero_copy = migrate_zero_copy_send();
 
-    for (i = 0; i < migrate_multifd_channels(); i++) {
+    for (i = 0; i < thread_count; i++) {
         MultiFDSendParams *p = &multifd_send_state->params[i];
 
         if (multifd_send_should_exit()) {
@@ -634,7 +636,7 @@ int multifd_send_sync_main(MultiFDSyncReq req)
         qatomic_set(&p->pending_sync, req);
         qemu_sem_post(&p->sem);
     }
-    for (i = 0; i < migrate_multifd_channels(); i++) {
+    for (i = 0; i < thread_count; i++) {
         MultiFDSendParams *p = &multifd_send_state->params[i];
 
         if (multifd_send_should_exit()) {
-- 
2.50.1 (Apple Git-155)