[Qemu-devel] [PATCH v2 4/4] Try not to exceed max downtime on stage3

[Liran Schour]

Move to stage3 only when remaining work can be done below max downtime.

Changes from v1: remove max iterations. Try to infer storage performance and by 
that calculate remaining work.

Signed-off-by: Liran Schour <address@hidden>
---
 block-migration.c |  136 +++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 132 insertions(+), 4 deletions(-)

diff --git a/block-migration.c b/block-migration.c
index 16df75f..5ef3eb8 100644
--- a/block-migration.c
+++ b/block-migration.c
@@ -17,6 +17,7 @@
 #include "qemu-queue.h"
 #include "monitor.h"
 #include "block-migration.h"
+#include "migration.h"
 #include <assert.h>
 
 #define BLOCK_SIZE (BDRV_SECTORS_PER_DIRTY_CHUNK << BDRV_SECTOR_BITS)
@@ -60,6 +61,7 @@ typedef struct BlkMigBlock {
     QEMUIOVector qiov;
     BlockDriverAIOCB *aiocb;
     int ret;
+    long double time;
     QSIMPLEQ_ENTRY(BlkMigBlock) entry;
 } BlkMigBlock;
 
@@ -74,11 +76,79 @@ typedef struct BlkMigState {
     int64_t total_sector_sum;
     int prev_progress;
     int bulk_completed;
-    int dirty_iterations;
+    long double total_time;
+    int reads;
 } BlkMigState;
 
 static BlkMigState block_mig_state;
 
+static int64_t get_clock_realtime(void)
+{
+    struct timeval tv;
+
+    gettimeofday(&tv, NULL);
+    return tv.tv_sec * 1000000000LL + (tv.tv_usec * 1000);
+}
+
+#ifdef WIN32
+
+static int64_t clock_freq;
+
+static void init_get_clock(void)
+{
+    LARGE_INTEGER freq;
+    int ret;
+    ret = QueryPerformanceFrequency(&freq);
+    if (ret == 0) {
+        fprintf(stderr, "Could not calibrate ticks\n");
+        exit(1);
+    }
+    clock_freq = freq.QuadPart;
+}
+
+static int64_t get_clock(void)
+{
+    LARGE_INTEGER ti;
+    QueryPerformanceCounter(&ti);
+    return muldiv64(ti.QuadPart, get_ticks_per_sec(), clock_freq);
+}
+
+#else
+
+static int use_rt_clock;
+
+static void init_get_clock(void)
+{
+    use_rt_clock = 0;
+#if defined(__linux__) || (defined(__FreeBSD__) && __FreeBSD_version >= 
500000) \
+    || defined(__DragonFly__) || defined(__FreeBSD_kernel__)
+    {
+        struct timespec ts;
+        if (clock_gettime(CLOCK_MONOTONIC, &ts) == 0) {
+            use_rt_clock = 1;
+        }
+    }
+#endif
+}
+
+static int64_t get_clock(void)
+{
+#if defined(__linux__) || (defined(__FreeBSD__) && __FreeBSD_version >= 
500000) \
+       || defined(__DragonFly__) || defined(__FreeBSD_kernel__)
+    if (use_rt_clock) {
+        struct timespec ts;
+        clock_gettime(CLOCK_MONOTONIC, &ts);
+        return ts.tv_sec * 1000000000LL + ts.tv_nsec;
+    } else
+#endif
+    {
+        /* XXX: using gettimeofday leads to problems if the date
+           changes, so it should be avoided. */
+        return get_clock_realtime();
+    }
+}
+#endif
+
 static void blk_send(QEMUFile *f, BlkMigBlock * blk)
 {
     int len;
@@ -127,12 +197,28 @@ uint64_t blk_mig_bytes_total(void)
     return sum << BDRV_SECTOR_BITS;
 }
 
+static inline void add_avg_read_time(long double time)
+{
+    block_mig_state.reads++;
+    block_mig_state.total_time += time;
+}
+
+static inline long double compute_read_bwidth(void)
+{
+    assert(block_mig_state.total_time != 0);
+    return  (block_mig_state.reads * BLOCK_SIZE)/ block_mig_state.total_time;
+}
+
 static void blk_mig_read_cb(void *opaque, int ret)
 {
     BlkMigBlock *blk = opaque;
 
     blk->ret = ret;
 
+    blk->time = get_clock() - blk->time;
+
+    add_avg_read_time(blk->time);
+
     QSIMPLEQ_INSERT_TAIL(&block_mig_state.blk_list, blk, entry);
 
     block_mig_state.submitted--;
@@ -182,6 +268,8 @@ static int mig_save_device_bulk(Monitor *mon, QEMUFile *f,
     blk->iov.iov_len = nr_sectors * BDRV_SECTOR_SIZE;
     qemu_iovec_init_external(&blk->qiov, &blk->iov, 1);
 
+    blk->time = get_clock();
+
     blk->aiocb = bdrv_aio_readv(bs, cur_sector, &blk->qiov,
                                 nr_sectors, blk_mig_read_cb, blk);
     if (!blk->aiocb) {
@@ -223,6 +311,8 @@ static void init_blk_migration(Monitor *mon, QEMUFile *f)
     block_mig_state.total_sector_sum = 0;
     block_mig_state.prev_progress = -1;
     block_mig_state.bulk_completed = 0;
+    block_mig_state.total_time = 0;
+    block_mig_state.reads = 0;
 
     for (bs = bdrv_first; bs != NULL; bs = bs->next) {
         if (bs->type == BDRV_TYPE_HD) {
@@ -321,6 +411,8 @@ static int mig_save_device_dirty(Monitor *mon, QEMUFile *f,
                 blk->iov.iov_base = blk->buf;
                 blk->iov.iov_len = nr_sectors * BDRV_SECTOR_SIZE;
                 qemu_iovec_init_external(&blk->qiov, &blk->iov, 1);
+
+               blk->time = get_clock();
 
                 blk->aiocb = bdrv_aio_readv(bmds->bs, sector, &blk->qiov,
                                             nr_sectors, blk_mig_read_cb, blk);
@@ -403,10 +495,42 @@ static void flush_blks(QEMUFile* f)
             block_mig_state.transferred);
 }
 
+static int64_t get_remaining_dirty(void)
+{
+    BlkMigDevState *bmds;
+    int64_t dirty = 0;
+
+    QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
+        dirty += bdrv_get_dirty_count(bmds->bs);
+    }
+
+    return dirty * BLOCK_SIZE;
+}
+
 static int is_stage2_completed(void)
 {
-    return (block_mig_state.submitted == 0 &&
-           block_mig_state.bulk_completed);
+    int64_t remaining_dirty;
+    long double bwidth;
+
+    if (block_mig_state.bulk_completed == 1) {
+
+        remaining_dirty = get_remaining_dirty();
+       if(remaining_dirty == 0) {
+           return 1;
+       }
+
+       bwidth = compute_read_bwidth();
+
+       if ((remaining_dirty / bwidth) <=
+            migrate_max_downtime()) {
+            /* finish stage2 because we think that we can finish remaing work
+               below max_downtime */
+
+            return 1;
+        }
+    }
+
+    return 0;
 }
 
 static void blk_mig_cleanup(Monitor *mon)
@@ -490,7 +614,9 @@ static int block_save_live(Monitor *mon, QEMUFile *f, int 
stage, void *opaque)
     }
 
     if (stage == 3) {
-        /* we now for sure that save bulk is completed */
+        /* we know for sure that save bulk is completed and
+           all async read completed */
+        assert(block_mig_state.submitted == 0);
 
         while(blk_mig_save_dirty_block(mon, f, 0) != 0);
         blk_mig_cleanup(mon);
@@ -580,4 +706,6 @@ void blk_mig_init(void)
 
     register_savevm_live("block", 0, 1, block_set_params, block_save_live,
                          NULL, block_load, &block_mig_state);
+
+    init_get_clock();
 }
-- 
1.6.0.4