From: Ivan Ren <ivanren@tencent.com>

This patch fix a multifd migration bug in migration speed calculation, this
problem can be reproduced as follows:
1. start a vm and give a heavy memory write stress to prevent the vm be
   successfully migrated to destination
2. begin a migration with multifd
3. migrate for a long time [actually, this can be measured by transferred bytes]
4. migrate cancel
5. begin a new migration with multifd, the migration will directly run into
   migration_completion phase

Reason as follows:

Migration update bandwidth and s->threshold_size in function
migration_update_counters after BUFFER_DELAY time:

    current_bytes = migration_total_bytes(s);
    transferred = current_bytes - s->iteration_initial_bytes;
    time_spent = current_time - s->iteration_start_time;
    bandwidth = (double)transferred / time_spent;
    s->threshold_size = bandwidth * s->parameters.downtime_limit;

In multifd migration, migration_total_bytes function return
qemu_ftell(s->to_dst_file) + ram_counters.multifd_bytes.
s->iteration_initial_bytes will be initialized to 0 at every new migration,
but ram_counters is a global variable, and history migration data will be
accumulated. So if the ram_counters.multifd_bytes is big enough, it may lead
pending_size >= s->threshold_size become false in migration_iteration_run
after the first migration_update_counters.

Signed-off-by: Ivan Ren <ivanren@tencent.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Suggested-by: Wei Yang <richardw.yang@linux.intel.com>
---
v1->v2:
- Add interface update_iteration_initial_status to update statistic fields
  at the same time to avoid info mismatch lead wrong calculation result.

 migration/migration.c | 25 +++++++++++++++++++------
 migration/savevm.c    |  1 +
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 8a607fe1e2..5db62ef9c8 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1908,6 +1908,11 @@ static bool migrate_prepare(MigrationState *s, bool blk, bool blk_inc,
     }
 
     migrate_init(s);
+    /*
+     * set ram_counters memory to zero for a
+     * new migration
+     */
+    memset(&ram_counters, 0, sizeof(ram_counters));
 
     return true;
 }
@@ -3025,6 +3030,17 @@ static void migration_calculate_complete(MigrationState *s)
     }
 }
 
+static update_iteration_initial_status(MigrationState *s)
+{
+    /*
+     * Update these three fields at the same time to avoid mismatch info lead
+     * wrong speed calculation.
+     */
+    s->iteration_start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
+    s->iteration_initial_bytes = migration_total_bytes(s);
+    s->iteration_initial_pages = ram_get_total_transferred_pages();
+}
+
 static void migration_update_counters(MigrationState *s,
                                       int64_t current_time)
 {
@@ -3060,9 +3076,7 @@ static void migration_update_counters(MigrationState *s,
 
     qemu_file_reset_rate_limit(s->to_dst_file);
 
-    s->iteration_start_time = current_time;
-    s->iteration_initial_bytes = current_bytes;
-    s->iteration_initial_pages = ram_get_total_transferred_pages();
+    update_iteration_initial_status(s);
 
     trace_migrate_transferred(transferred, time_spent,
                               bandwidth, s->threshold_size);
@@ -3186,7 +3200,7 @@ static void *migration_thread(void *opaque)
     rcu_register_thread();
 
     object_ref(OBJECT(s));
-    s->iteration_start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
+    update_iteration_initial_status(s);
 
     qemu_savevm_state_header(s->to_dst_file);
 
@@ -3251,8 +3265,7 @@ static void *migration_thread(void *opaque)
              * the local variables. This is important to avoid
              * breaking transferred_bytes and bandwidth calculation
              */
-            s->iteration_start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
-            s->iteration_initial_bytes = 0;
+            update_iteration_initial_status(s);
         }
 
         current_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
diff --git a/migration/savevm.c b/migration/savevm.c
index 79ed44d475..480c511b19 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1424,6 +1424,7 @@ static int qemu_savevm_state(QEMUFile *f, Error **errp)
     }
 
     migrate_init(ms);
+    memset(&ram_counters, 0, sizeof(ram_counters));
     ms->to_dst_file = f;
 
     qemu_mutex_unlock_iothread();
-- 
2.17.2 (Apple Git-113)

Patchew URL: https://patchew.org/QEMU/1564736786-26495-1-git-send-email-ivanren@tencent.com/



Hi,

This series failed build test on s390x host. Please find the details below.

=== TEST SCRIPT BEGIN ===
#!/bin/bash
# Testing script will be invoked under the git checkout with
# HEAD pointing to a commit that has the patches applied on top of "base"
# branch
set -e

echo
echo "=== ENV ==="
env

echo
echo "=== PACKAGES ==="
rpm -qa

echo
echo "=== UNAME ==="
uname -a

CC=$HOME/bin/cc
INSTALL=$PWD/install
BUILD=$PWD/build
mkdir -p $BUILD $INSTALL
SRC=$PWD
cd $BUILD
$SRC/configure --cc=$CC --prefix=$INSTALL
make -j4
# XXX: we need reliable clean up
# make check -j4 V=1
make install
=== TEST SCRIPT END ===

  CC      migration/channel.o
  CC      migration/savevm.o
  CC      migration/colo.o
/var/tmp/patchew-tester-tmp-xf2xxfrc/src/migration/migration.c:3033:8: error: return type defaults to ‘int’ [-Werror=implicit-int]
 3033 | static update_iteration_initial_status(MigrationState *s)
      |        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/var/tmp/patchew-tester-tmp-xf2xxfrc/src/migration/migration.c: In function ‘update_iteration_initial_status’:
/var/tmp/patchew-tester-tmp-xf2xxfrc/src/migration/migration.c:3042:1: error: control reaches end of non-void function [-Werror=return-type]
 3042 | }
      | ^
cc1: all warnings being treated as errors


The full log is available at
http://patchew.org/logs/1564736786-26495-1-git-send-email-ivanren@tencent.com/testing.s390x/?type=message.
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Please send your feedback to patchew-devel@redhat.com

Patchew URL: https://patchew.org/QEMU/1564736786-26495-1-git-send-email-ivanren@tencent.com/



Hi,

This series failed the asan build test. Please find the testing commands and
their output below. If you have Docker installed, you can probably reproduce it
locally.

=== TEST SCRIPT BEGIN ===
#!/bin/bash
make docker-image-fedora V=1 NETWORK=1
time make docker-test-debug@fedora TARGET_LIST=x86_64-softmmu J=14 NETWORK=1
=== TEST SCRIPT END ===

  AS      pc-bios/optionrom/multiboot.o
  CC      qga/commands-posix.o
  AS      pc-bios/optionrom/linuxboot.o
/tmp/qemu-test/src/migration/migration.c:3033:8: error: type specifier missing, defaults to 'int' [-Werror,-Wimplicit-int]
static update_iteration_initial_status(MigrationState *s)
~~~~~~ ^
/tmp/qemu-test/src/migration/migration.c:3042:1: error: control reaches end of non-void function [-Werror,-Wreturn-type]
}
^
2 errors generated.


The full log is available at
http://patchew.org/logs/1564736786-26495-1-git-send-email-ivanren@tencent.com/testing.asan/?type=message.
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Please send your feedback to patchew-devel@redhat.com