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Sun, 29 Sep 2024 10:14:44 -0700 (PDT) From: yong.huang@smartx.com To: qemu-devel@nongnu.org Cc: Peter Xu , Fabiano Rosas , Eric Blake , Markus Armbruster , Paolo Bonzini , yong.huang@smartx.com Subject: [PATCH v2 1/3] migration: Support background ramblock dirty sync Date: Mon, 30 Sep 2024 01:14:26 +0800 Message-Id: X-Mailer: git-send-email 2.27.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2607:f8b0:4864:20::536; envelope-from=yong.huang@smartx.com; helo=mail-pg1-x536.google.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @smartx-com.20230601.gappssmtp.com) X-ZM-MESSAGEID: 1727630177194116600 Content-Type: text/plain; charset="utf-8" From: Hyman Huang When VM is configured with huge memory, the current throttle logic doesn't look like to scale, because migration_trigger_throttle() is only called for each iteration, so it won't be invoked for a long time if one iteration can take a long time. The background dirty sync aim to fix the above issue by synchronizing the ramblock from remote dirty bitmap and, when necessary, triggering the CPU throttle multiple times during a long iteration. This is a trade-off between synchronization overhead and CPU throttle impact. Signed-off-by: Hyman Huang --- include/migration/misc.h | 3 ++ migration/migration.c | 11 +++++++ migration/ram.c | 64 ++++++++++++++++++++++++++++++++++++ migration/ram.h | 3 ++ migration/trace-events | 1 + system/cpu-timers.c | 2 ++ tests/qtest/migration-test.c | 29 ++++++++++++++++ 7 files changed, 113 insertions(+) diff --git a/include/migration/misc.h b/include/migration/misc.h index bfadc5613b..67c00d98f5 100644 --- a/include/migration/misc.h +++ b/include/migration/misc.h @@ -111,4 +111,7 @@ bool migration_in_bg_snapshot(void); /* migration/block-dirty-bitmap.c */ void dirty_bitmap_mig_init(void); =20 +/* migration/ram.c */ +void bg_ram_dirty_sync_init(void); + #endif diff --git a/migration/migration.c b/migration/migration.c index 3dea06d577..224b5dfb4f 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -3285,6 +3285,9 @@ static void migration_iteration_finish(MigrationState= *s) { /* If we enabled cpu throttling for auto-converge, turn it off. */ cpu_throttle_stop(); + if (migrate_auto_converge()) { + bg_ram_dirty_sync_timer_enable(false); + } =20 bql_lock(); switch (s->state) { @@ -3526,6 +3529,14 @@ static void *migration_thread(void *opaque) =20 trace_migration_thread_setup_complete(); =20 + /* + * Tick the background ramblock dirty sync timer after setup + * phase. + */ + if (migrate_auto_converge()) { + bg_ram_dirty_sync_timer_enable(true); + } + while (migration_is_active()) { if (urgent || !migration_rate_exceeded(s->to_dst_file)) { MigIterateState iter_state =3D migration_iteration_run(s); diff --git a/migration/ram.c b/migration/ram.c index 67ca3d5d51..995bae1ac9 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -110,6 +110,12 @@ */ #define MAPPED_RAM_LOAD_BUF_SIZE 0x100000 =20 +/* Background ramblock dirty sync trigger every five seconds */ +#define BG_RAM_SYNC_TIMESLICE_MS 5000 +#define BG_RAM_SYNC_TIMER_INTERVAL_MS 1000 + +static QEMUTimer *bg_ram_dirty_sync_timer; + XBZRLECacheStats xbzrle_counters; =20 /* used by the search for pages to send */ @@ -4543,6 +4549,64 @@ static void ram_mig_ram_block_resized(RAMBlockNotifi= er *n, void *host, } } =20 +static void bg_ram_dirty_sync_timer_tick(void *opaque) +{ + static int prev_pct; + static uint64_t prev_sync_cnt =3D 2; + uint64_t sync_cnt =3D stat64_get(&mig_stats.dirty_sync_count); + int cur_pct =3D cpu_throttle_get_percentage(); + + if (prev_pct && !cur_pct) { + /* CPU throttle timer stopped, so do we */ + return; + } + + /* + * The first iteration copies all memory anyhow and has no + * effect on guest performance, therefore omit it to avoid + * paying extra for the sync penalty. + */ + if (sync_cnt <=3D 1) { + goto end; + } + + if (sync_cnt =3D=3D prev_sync_cnt) { + int64_t curr_time =3D qemu_clock_get_ms(QEMU_CLOCK_REALTIME); + assert(ram_state); + if ((curr_time - ram_state->time_last_bitmap_sync) > + BG_RAM_SYNC_TIMESLICE_MS) { + trace_bg_ram_dirty_sync(); + WITH_RCU_READ_LOCK_GUARD() { + migration_bitmap_sync_precopy(ram_state, false); + } + } + } + +end: + prev_sync_cnt =3D stat64_get(&mig_stats.dirty_sync_count); + prev_pct =3D cpu_throttle_get_percentage(); + + timer_mod(bg_ram_dirty_sync_timer, + qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL_RT) + + BG_RAM_SYNC_TIMER_INTERVAL_MS); +} + +void bg_ram_dirty_sync_timer_enable(bool enable) +{ + if (enable) { + bg_ram_dirty_sync_timer_tick(NULL); + } else { + timer_del(bg_ram_dirty_sync_timer); + } +} + +void bg_ram_dirty_sync_init(void) +{ + bg_ram_dirty_sync_timer =3D + timer_new_ms(QEMU_CLOCK_VIRTUAL_RT, + bg_ram_dirty_sync_timer_tick, NULL); +} + static RAMBlockNotifier ram_mig_ram_notifier =3D { .ram_block_resized =3D ram_mig_ram_block_resized, }; diff --git a/migration/ram.h b/migration/ram.h index bc0318b834..9c1a2f30f1 100644 --- a/migration/ram.h +++ b/migration/ram.h @@ -93,4 +93,7 @@ void ram_write_tracking_prepare(void); int ram_write_tracking_start(void); void ram_write_tracking_stop(void); =20 +/* Background ramblock dirty sync */ +void bg_ram_dirty_sync_timer_enable(bool enable); + #endif diff --git a/migration/trace-events b/migration/trace-events index c65902f042..3f09e7f383 100644 --- a/migration/trace-events +++ b/migration/trace-events @@ -90,6 +90,7 @@ put_qlist_end(const char *field_name, const char *vmsd_na= me) "%s(%s)" qemu_file_fclose(void) "" =20 # ram.c +bg_ram_dirty_sync(void) "" get_queued_page(const char *block_name, uint64_t tmp_offset, unsigned long= page_abs) "%s/0x%" PRIx64 " page_abs=3D0x%lx" get_queued_page_not_dirty(const char *block_name, uint64_t tmp_offset, uns= igned long page_abs) "%s/0x%" PRIx64 " page_abs=3D0x%lx" migration_bitmap_sync_start(void) "" diff --git a/system/cpu-timers.c b/system/cpu-timers.c index 0b31c9a1b6..64f0834be4 100644 --- a/system/cpu-timers.c +++ b/system/cpu-timers.c @@ -25,6 +25,7 @@ #include "qemu/osdep.h" #include "qemu/cutils.h" #include "migration/vmstate.h" +#include "migration/misc.h" #include "qapi/error.h" #include "qemu/error-report.h" #include "sysemu/cpus.h" @@ -274,4 +275,5 @@ void cpu_timers_init(void) vmstate_register(NULL, 0, &vmstate_timers, &timers_state); =20 cpu_throttle_init(); + bg_ram_dirty_sync_init(); } diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c index d6768d5d71..3296f5244d 100644 --- a/tests/qtest/migration-test.c +++ b/tests/qtest/migration-test.c @@ -468,6 +468,12 @@ static void migrate_ensure_converge(QTestState *who) migrate_set_parameter_int(who, "downtime-limit", 30 * 1000); } =20 +static void migrate_ensure_iteration_last_long(QTestState *who) +{ + /* Set 10Byte/s bandwidth limit to make the iteration last long enough= */ + migrate_set_parameter_int(who, "max-bandwidth", 10); +} + /* * Our goal is to ensure that we run a single full migration * iteration, and also dirty memory, ensuring that at least @@ -2791,6 +2797,7 @@ static void test_migrate_auto_converge(void) * so we need to decrease a bandwidth. */ const int64_t init_pct =3D 5, inc_pct =3D 25, max_pct =3D 95; + uint64_t prev_dirty_sync_cnt, dirty_sync_cnt; =20 if (test_migrate_start(&from, &to, uri, &args)) { return; @@ -2827,6 +2834,28 @@ static void test_migrate_auto_converge(void) } while (true); /* The first percentage of throttling should be at least init_pct */ g_assert_cmpint(percentage, >=3D, init_pct); + + /* Make sure the iteration last a long time enough */ + migrate_ensure_iteration_last_long(from); + + /* + * End the loop when the dirty sync count greater than 1. + */ + while ((dirty_sync_cnt =3D get_migration_pass(from)) < 2) { + usleep(1000 * 1000); + } + + prev_dirty_sync_cnt =3D dirty_sync_cnt; + + /* + * The dirty sync count must changes in 5 seconds, here we + * plus 1 second as error value. + */ + sleep(5 + 1); + + dirty_sync_cnt =3D get_migration_pass(from); + g_assert_cmpint(dirty_sync_cnt, !=3D , prev_dirty_sync_cnt); + /* Now, when we tested that throttling works, let it converge */ migrate_ensure_converge(from); =20 --=20 2.27.0