From: Peter Xu <peterx@redhat.com>
Date: Fri, 13 Jun 2025 14:12:09 +0000 (-0400)
Subject: migration/postcopy: Bring blocktime layer to ns level
X-Git-Tag: v10.1.0-rc0~25^2~9
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a098761f63e019b75a23575bb8d5a520c0dbce64;p=thirdparty%2Fqemu.git

migration/postcopy: Bring blocktime layer to ns level

With 64-bit fields, it is trivial.  The caution is when exposing any values
in QMP, it was still declared with milliseconds (ms).  Hence it's needed to
do the convertion when exporting the values to existing QMP queries.

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20250613141217.474825-7-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
---

diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index e9acb4ef6e..9dfa92a62d 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -110,6 +110,7 @@ void postcopy_thread_create(MigrationIncomingState *mis,
 #include <sys/eventfd.h>
 #include <linux/userfaultfd.h>
 
+/* All the time records are in unit of nanoseconds */
 typedef struct PostcopyBlocktimeContext {
     /* time when page fault initiated per vCPU */
     uint64_t *vcpu_blocktime_start;
@@ -168,7 +169,9 @@ static uint32List *get_vcpu_blocktime_list(PostcopyBlocktimeContext *ctx)
     int i;
 
     for (i = ms->smp.cpus - 1; i >= 0; i--) {
-        QAPI_LIST_PREPEND(list, (uint32_t)ctx->vcpu_blocktime_total[i]);
+        /* Convert ns -> ms */
+        QAPI_LIST_PREPEND(
+            list, (uint32_t)(ctx->vcpu_blocktime_total[i] / SCALE_MS));
     }
 
     return list;
@@ -191,7 +194,8 @@ void fill_destination_postcopy_migration_info(MigrationInfo *info)
     }
 
     info->has_postcopy_blocktime = true;
-    info->postcopy_blocktime = (uint32_t)bc->total_blocktime;
+    /* Convert ns -> ms */
+    info->postcopy_blocktime = (uint32_t)(bc->total_blocktime / SCALE_MS);
     info->has_postcopy_vcpu_blocktime = true;
     info->postcopy_vcpu_blocktime = get_vcpu_blocktime_list(bc);
 }
@@ -816,9 +820,9 @@ static int get_mem_fault_cpu_index(uint32_t pid)
     return -1;
 }
 
-static uint64_t get_low_time_offset(void)
+static uint64_t get_current_ns(void)
 {
-    return (uint64_t)qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
+    return (uint64_t)qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
 }
 
 /*
@@ -835,7 +839,7 @@ void mark_postcopy_blocktime_begin(uintptr_t addr, uint32_t ptid,
     int cpu;
     MigrationIncomingState *mis = migration_incoming_get_current();
     PostcopyBlocktimeContext *dc = mis->blocktime_ctx;
-    uint64_t low_time_offset;
+    uint64_t current;
 
     if (!dc || ptid == 0) {
         return;
@@ -845,13 +849,13 @@ void mark_postcopy_blocktime_begin(uintptr_t addr, uint32_t ptid,
         return;
     }
 
-    low_time_offset = get_low_time_offset();
+    current = get_current_ns();
     if (dc->vcpu_addr[cpu] == 0) {
         dc->smp_cpus_down++;
     }
 
-    dc->last_begin = low_time_offset;
-    dc->vcpu_blocktime_start[cpu] = low_time_offset;
+    dc->last_begin = current;
+    dc->vcpu_blocktime_start[cpu] = current;
     dc->vcpu_addr[cpu] = addr;
 
     /*
@@ -899,13 +903,13 @@ static void mark_postcopy_blocktime_end(uintptr_t addr)
     unsigned int smp_cpus = ms->smp.cpus;
     int i, affected_cpu = 0;
     bool vcpu_total_blocktime = false;
-    uint64_t read_vcpu_time, low_time_offset;
+    uint64_t read_vcpu_time, current;
 
     if (!dc) {
         return;
     }
 
-    low_time_offset = get_low_time_offset();
+    current = get_current_ns();
     /* lookup cpu, to clear it,
      * that algorithm looks straightforward, but it's not
      * optimal, more optimal algorithm is keeping tree or hash
@@ -918,7 +922,7 @@ static void mark_postcopy_blocktime_end(uintptr_t addr)
             continue;
         }
         dc->vcpu_addr[i] = 0;
-        vcpu_blocktime = low_time_offset - read_vcpu_time;
+        vcpu_blocktime = current - read_vcpu_time;
         affected_cpu += 1;
         /* we need to know is that mark_postcopy_end was due to
          * faulted page, another possible case it's prefetched
@@ -932,7 +936,7 @@ static void mark_postcopy_blocktime_end(uintptr_t addr)
 
     dc->smp_cpus_down -= affected_cpu;
     if (vcpu_total_blocktime) {
-        dc->total_blocktime += low_time_offset - dc->last_begin;
+        dc->total_blocktime += current - dc->last_begin;
     }
     trace_mark_postcopy_blocktime_end(addr, dc->total_blocktime,
                                       affected_cpu);