[PATCH v4 0/2] support dirtyrate measurement with dirty bitmap

[PATCH v4 0/2] support dirtyrate measurement with dirty bitmap

[huangy81]

From: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>

v4:
- drop the first commit:
  "KVM: introduce kvm_get_manual_dirty_log_protect"

- clear dirty log unconditionally so that the first commit
  can be dropped.

- rename global var DirtyRateDirtyPages to total_dirty_pages

- stat the dirty pages along with the existing loop in
  cpu_physical_memory_set_dirty_lebitmap

- stat the increased dirty pages like the way of dirty-ring

- add BQL when fetch dirty log and clear dirty log

- do not clear dirty log after measuring.

v4 implementation clear log unconditionally so that the
kvm_get_manual_dirty_log_protect can be dropped and so do the
first commit.

other main modification is add the BQL when fetch and clear
dirty log.

last modification is do not clear dirty log after measuring.
if dirty tracking be stopped after measuring, clear dirty
log make no sense.if dirty tracking is running after mesauring,
clear dirty log can be handled by the caller who is interested in it.

v3:
- do not touch cpu_physical_memory_sync_dirty_bitmap

- rename global var DirtyRateIncreasedPages to DirtyRateDirtyPages

- stat dirty pages in cpu_physical_memory_set_dirty_lebitmap, which
  is on the execution path of memory_global_dirty_log_sync and can
  be used for dirty rate measuring.

the v3 implemention runs well, we could get accurate dirtyrate
as v1 and simplify the implementation heavyly. it do not touch
the any ram_list.dirty_memory[*], so do has no conflict with migraion
at all.
if migration is running at the same time with dirtyrate measuring,
measuring may reset protection of pages after
memory_global_dirty_log_sync before migration iteration, but it has
no side affect because kvm_log_clear_one_slot can guarantee that
same dirty_bmap in a slot shouldn't be cleared twice.

v2:
- drop the DIRTY_MEMORY_DIRTY_RATE dirty bits

- reuse the DIRTY_MEMORY_MIGRATION dirty bits to stat the dirty
  pages.

- introduce global var DirtyRateIncreasedPages to stat the
  increased dirty pages

- simplify the logic of calculation. skip the 1'round of
  log sync unconditionally

changes of this version are based on Peter's advice,
like the version 1, it is posted for the sake of RFC.
ideally, this patshset may be merged after the commit:
"migration/dirtyrate: implement dirty-ring dirtyrate calculation"

v1:
the dirtyrate measurement implemented by page-sampling originally, it
is not accurate in some scenarios, so we have introduced dirty-ring
based dirtyrate measurement(maybe it will be merged soon), it fix the
accuracy of page-sampling, and more importantly, it is at the
granualrity of vcpu.

dirty-ring method can be used when dirty-ring enable, as supplementary,
we introduce dirty-bitmap method to calculating dirtyrate when dirty log
enable, so that we can also get the accurate dirtyrate if needed in the
absence of dirty-ring.

three things has done to implement the measurement:
- introduce a fresh new dirty bits named DIRTY_MEMORY_DIRTY_RATE, which
  is used to store dirty bitmap after fetching it from kvm. why we do
  not reuse the existing DIRTY_MEMORY_MIGRATION dirty bits is we do not
  want to interfere with migration of and let implementation clear, this
  is also the reason why dirty_memory be split.

  DIRTY_MEMORY_DIRTY_RATE dirty bits will be filled when
  memory_global_dirty_log_sync executed if GLOBAL_DIRTY_DIRTY_RATE bit
  be set in the global_dirty_tracking flag.

- introduce kvm_get_manual_dirty_log_protect function so that we can
  probe the protect caps of kvm when calculating.

- implement dirtyrate measurement with dirty bitmap with following step:
  1. start the dirty log.

  2. probe the protect cap, if KVM_DIRTY_LOG_INITIALLY_SET enable, skip
     skip the 1'R and do the reset page protection manually, since kvm
     file bitmap with 1 bits if this cap is enabled.

  3. clear the DIRTY_MEMORY_DIRTY_RATE dirty bits, prepare to store
     the dirty bitmap.

  4. start memory_global_dirty_log_sync and fetch dirty bitmap from kvm

  5. reap the DIRTY_MEMORY_DIRTY_RATE dirty bits and do the calculation.

this patchset rebases on the commit
"migration/dirtyrate: implement dirty-ring dirtyrate calculation",
since the above feature has not been merged, so we post this patch
for the sake of RFC. ideally, this patshset may be merged after it.

Please, review, thanks !

Best Regards !

Hyman Huang(黄勇) (2):
  memory: introduce total_dirty_pages to stat dirty pages
  migration/dirtyrate: implement dirty-bitmap dirtyrate calculation

 hmp-commands.hx         |   9 ++--
 include/exec/ram_addr.h |   4 ++
 migration/dirtyrate.c   | 124 ++++++++++++++++++++++++++++++++++++++++++++----
 qapi/migration.json     |   6 ++-
 4 files changed, 128 insertions(+), 15 deletions(-)

-- 
1.8.3.1

[PATCH v4 1/2] memory: introduce total_dirty_pages to stat dirty pages

[huangy81]

From: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>

introduce global var total_dirty_pages to stat dirty pages
along with memory_global_dirty_log_sync.

Signed-off-by: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>
---
 include/exec/ram_addr.h | 4 ++++
 migration/dirtyrate.c   | 7 +++++++
 2 files changed, 11 insertions(+)

diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
index 45c9132..e98d665 100644
--- a/include/exec/ram_addr.h
+++ b/include/exec/ram_addr.h
@@ -26,6 +26,8 @@
 #include "exec/ramlist.h"
 #include "exec/ramblock.h"
 
+extern uint64_t total_dirty_pages;
+
 /**
  * clear_bmap_size: calculate clear bitmap size
  *
@@ -366,6 +368,7 @@ static inline void cpu_physical_memory_set_dirty_lebitmap(unsigned long *bitmap,
             for (k = 0; k < nr; k++) {
                 if (bitmap[k]) {
                     unsigned long temp = leul_to_cpu(bitmap[k]);
+                    total_dirty_pages += ctpopl(temp);
 
                     qatomic_or(&blocks[DIRTY_MEMORY_VGA][idx][offset], temp);
 
@@ -403,6 +406,7 @@ static inline void cpu_physical_memory_set_dirty_lebitmap(unsigned long *bitmap,
         for (i = 0; i < len; i++) {
             if (bitmap[i] != 0) {
                 c = leul_to_cpu(bitmap[i]);
+                total_dirty_pages += ctpopl(c);
                 do {
                     j = ctzl(c);
                     c &= ~(1ul << j);
diff --git a/migration/dirtyrate.c b/migration/dirtyrate.c
index f92c4b4..17b3d2c 100644
--- a/migration/dirtyrate.c
+++ b/migration/dirtyrate.c
@@ -28,6 +28,13 @@
 #include "sysemu/runstate.h"
 #include "exec/memory.h"
 
+/*
+ * total_dirty_pages is procted by BQL and is used
+ * to stat dirty pages during the period of two
+ * memory_global_dirty_log_sync
+ */
+uint64_t total_dirty_pages;
+
 typedef struct DirtyPageRecord {
     uint64_t start_pages;
     uint64_t end_pages;
-- 
1.8.3.1

[PATCH v4 2/2] migration/dirtyrate: implement dirty-bitmap dirtyrate calculation

[huangy81]

From: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>

introduce dirty-bitmap mode as the third method of calc-dirty-rate.
implement dirty-bitmap dirtyrate calculation, which can be used
to measuring dirtyrate in the absence of dirty-ring.

introduce "dirty_bitmap:-b" option in hmp calc_dirty_rate to
indicate dirty bitmap method should be used for calculation.

Signed-off-by: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>
---
 hmp-commands.hx       |   9 ++--
 migration/dirtyrate.c | 117 ++++++++++++++++++++++++++++++++++++++++++++++----
 qapi/migration.json   |   6 ++-
 3 files changed, 117 insertions(+), 15 deletions(-)

diff --git a/hmp-commands.hx b/hmp-commands.hx
index f7fc9d7..605973c 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -1738,9 +1738,10 @@ ERST
 
     {
         .name       = "calc_dirty_rate",
-        .args_type  = "dirty_ring:-r,second:l,sample_pages_per_GB:l?",
-        .params     = "[-r] second [sample_pages_per_GB]",
-        .help       = "start a round of guest dirty rate measurement (using -d to"
-                      "\n\t\t\t specify dirty ring as the method of calculation)",
+        .args_type  = "dirty_ring:-r,dirty_bitmap:-b,second:l,sample_pages_per_GB:l?",
+        .params     = "[-r] [-b] second [sample_pages_per_GB]",
+        .help       = "start a round of guest dirty rate measurement (using -r to"
+                      "\n\t\t\t specify dirty ring as the method of calculation and"
+                      "\n\t\t\t -b to specify dirty bitmap as method of calculation)",
         .cmd        = hmp_calc_dirty_rate,
     },
diff --git a/migration/dirtyrate.c b/migration/dirtyrate.c
index 17b3d2c..5b66650 100644
--- a/migration/dirtyrate.c
+++ b/migration/dirtyrate.c
@@ -15,6 +15,7 @@
 #include "qapi/error.h"
 #include "cpu.h"
 #include "exec/ramblock.h"
+#include "exec/ram_addr.h"
 #include "qemu/rcu_queue.h"
 #include "qemu/main-loop.h"
 #include "qapi/qapi-commands-migration.h"
@@ -118,6 +119,10 @@ static struct DirtyRateInfo *query_dirty_rate_info(void)
             }
             info->vcpu_dirty_rate = head;
         }
+
+        if (dirtyrate_mode == DIRTY_RATE_MEASURE_MODE_DIRTY_BITMAP) {
+            info->sample_pages = 0;
+        }
     }
 
     trace_query_dirty_rate_info(DirtyRateStatus_str(CalculatingState));
@@ -416,6 +421,13 @@ static void dirtyrate_global_dirty_log_stop(void)
     qemu_mutex_unlock_iothread();
 }
 
+static void dirtyrate_global_dirty_log_sync(void)
+{
+    qemu_mutex_lock_iothread();
+    memory_global_dirty_log_sync();
+    qemu_mutex_unlock_iothread();
+}
+
 static int64_t do_calculate_dirtyrate_vcpu(DirtyPageRecord dirty_pages)
 {
     uint64_t memory_size_MB;
@@ -429,6 +441,77 @@ static int64_t do_calculate_dirtyrate_vcpu(DirtyPageRecord dirty_pages)
     return memory_size_MB / time_s;
 }
 
+static inline void record_dirtypages_bitmap(DirtyPageRecord *dirty_pages,
+                                            bool start)
+{
+    if (start) {
+        dirty_pages->start_pages = total_dirty_pages;
+    } else {
+        dirty_pages->end_pages = total_dirty_pages;
+    }
+}
+
+static void do_calculate_dirtyrate_bitmap(DirtyPageRecord dirty_pages)
+{
+    DirtyStat.dirty_rate = do_calculate_dirtyrate_vcpu(dirty_pages);
+}
+
+static inline void dirtyrate_manual_reset_protect(void)
+{
+    RAMBlock *block = NULL;
+
+    qemu_mutex_lock_iothread();
+    WITH_RCU_READ_LOCK_GUARD() {
+        RAMBLOCK_FOREACH_MIGRATABLE(block) {
+            memory_region_clear_dirty_bitmap(block->mr, 0,
+                                             block->used_length);
+        }
+    }
+    qemu_mutex_unlock_iothread();
+}
+
+static void calculate_dirtyrate_dirty_bitmap(struct DirtyRateConfig config)
+{
+    int64_t msec = 0;
+    int64_t start_time;
+    DirtyPageRecord dirty_pages;
+
+    dirtyrate_global_dirty_log_start();
+
+    /*
+     * 1'round of log sync may return all 1 bits with
+     * KVM_DIRTY_LOG_INITIALLY_SET enable
+     * skip it unconditionally and start dirty tracking
+     * from 2'round of log sync
+     */
+    dirtyrate_global_dirty_log_sync();
+
+    /*
+     * reset page protect manually and unconditionally.
+     * this make sure kvm dirty log be cleared if
+     * KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE cap is enabled.
+     */
+    dirtyrate_manual_reset_protect();
+
+    record_dirtypages_bitmap(&dirty_pages, true);
+
+    start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
+    DirtyStat.start_time = start_time / 1000;
+
+    msec = config.sample_period_seconds * 1000;
+    msec = set_sample_page_period(msec, start_time);
+    DirtyStat.calc_time = msec / 1000;
+
+    /* fetch dirty bitmap from kvm */
+    dirtyrate_global_dirty_log_sync();
+
+    record_dirtypages_bitmap(&dirty_pages, false);
+
+    do_calculate_dirtyrate_bitmap(dirty_pages);
+
+    dirtyrate_global_dirty_log_stop();
+}
+
 static void calculate_dirtyrate_dirty_ring(struct DirtyRateConfig config)
 {
     CPUState *cpu;
@@ -514,7 +597,9 @@ out:
 
 static void calculate_dirtyrate(struct DirtyRateConfig config)
 {
-    if (config.mode == DIRTY_RATE_MEASURE_MODE_DIRTY_RING) {
+    if (config.mode == DIRTY_RATE_MEASURE_MODE_DIRTY_BITMAP) {
+        calculate_dirtyrate_dirty_bitmap(config);
+    } else if (config.mode == DIRTY_RATE_MEASURE_MODE_DIRTY_RING) {
         calculate_dirtyrate_dirty_ring(config);
     } else {
         calculate_dirtyrate_sample_vm(config);
@@ -597,12 +682,15 @@ void qmp_calc_dirty_rate(int64_t calc_time,
 
     /*
      * dirty ring mode only works when kvm dirty ring is enabled.
+     * on the contrary, dirty bitmap mode is not.
      */
-    if ((mode == DIRTY_RATE_MEASURE_MODE_DIRTY_RING) &&
-        !kvm_dirty_ring_enabled()) {
-        error_setg(errp, "dirty ring is disabled, use sample-pages method "
-                         "or remeasure later.");
-        return;
+    if (((mode == DIRTY_RATE_MEASURE_MODE_DIRTY_RING) &&
+        !kvm_dirty_ring_enabled()) ||
+        ((mode == DIRTY_RATE_MEASURE_MODE_DIRTY_BITMAP) &&
+         kvm_dirty_ring_enabled())) {
+        error_setg(errp, "mode %s is not enabled, use other method instead.",
+                         DirtyRateMeasureMode_str(mode));
+         return;
     }
 
     /*
@@ -678,9 +766,8 @@ void hmp_calc_dirty_rate(Monitor *mon, const QDict *qdict)
     int64_t sample_pages = qdict_get_try_int(qdict, "sample_pages_per_GB", -1);
     bool has_sample_pages = (sample_pages != -1);
     bool dirty_ring = qdict_get_try_bool(qdict, "dirty_ring", false);
-    DirtyRateMeasureMode mode =
-        (dirty_ring ? DIRTY_RATE_MEASURE_MODE_DIRTY_RING :
-         DIRTY_RATE_MEASURE_MODE_PAGE_SAMPLING);
+    bool dirty_bitmap = qdict_get_try_bool(qdict, "dirty_bitmap", false);
+    DirtyRateMeasureMode mode = DIRTY_RATE_MEASURE_MODE_PAGE_SAMPLING;
     Error *err = NULL;
 
     if (!sec) {
@@ -688,6 +775,18 @@ void hmp_calc_dirty_rate(Monitor *mon, const QDict *qdict)
         return;
     }
 
+    if (dirty_ring && dirty_bitmap) {
+        monitor_printf(mon, "Either dirty ring or dirty bitmap "
+                       "can be specified!\n");
+        return;
+    }
+
+    if (dirty_bitmap) {
+        mode = DIRTY_RATE_MEASURE_MODE_DIRTY_BITMAP;
+    } else if (dirty_ring) {
+        mode = DIRTY_RATE_MEASURE_MODE_DIRTY_RING;
+    }
+
     qmp_calc_dirty_rate(sec, has_sample_pages, sample_pages, true,
                         mode, &err);
     if (err) {
diff --git a/qapi/migration.json b/qapi/migration.json
index de35528..0b00976 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -1747,13 +1747,15 @@
 #
 # @page-sampling: calculate dirtyrate by sampling pages.
 #
-# @dirty-ring: calculate dirtyrate by via dirty ring.
+# @dirty-ring: calculate dirtyrate by dirty ring.
+#
+# @dirty-bitmap: calculate dirtyrate by dirty bitmap.
 #
 # Since: 6.1
 #
 ##
 { 'enum': 'DirtyRateMeasureMode',
-  'data': ['page-sampling', 'dirty-ring'] }
+  'data': ['page-sampling', 'dirty-ring', 'dirty-bitmap'] }
 
 ##
 # @DirtyRateInfo:
-- 
1.8.3.1