From 8e8f421cce99543081f225acf46541312cfbc371 Mon Sep 17 00:00:00 2001

From: Laurent Vivier <lvivier@redhat.com>

Date: Tue, 17 Mar 2020 17:05:18 +0000

Subject: [PATCH 1/2] migration: Rate limit inside host pages

RH-Author: Laurent Vivier <lvivier@redhat.com>

Message-id: <20200317170518.9303-1-lvivier@redhat.com>

Patchwork-id: 94374

O-Subject: [RHEL-AV-8.2.0 qemu-kvm PATCH] migration: Rate limit inside host pages

Bugzilla: 1814336

RH-Acked-by: Peter Xu <peterx@redhat.com>

RH-Acked-by: Juan Quintela <quintela@redhat.com>

RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

When using hugepages, rate limiting is necessary within each huge

page, since a 1G huge page can take a significant time to send, so

you end up with bursty behaviour.

Fixes: 4c011c37ecb3 ("postcopy: Send whole huge pages")

Reported-by: Lin Ma <LMa@suse.com>

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

Reviewed-by: Peter Xu <peterx@redhat.com>

Signed-off-by: Juan Quintela <quintela@redhat.com>

(cherry picked from commit 97e1e06780e70f6e98a0d2df881e0c0927d3aeb6)

Signed-off-by: Laurent Vivier <lvivier@redhat.com>

BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1814336

BRANCH: rhel-av-8.2.0

UPSTREAM: Merged

BREW: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=27283241

TESTED: Tested that the migration abort doesn't trigger an error message in

        the kernel logs on P9

Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>

---

 migration/migration.c  | 57 ++++++++++++++++++++++++++++----------------------

 migration/migration.h  |  1 +

 migration/ram.c        |  2 ++

 migration/trace-events |  4 ++--

 4 files changed, 37 insertions(+), 27 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c

index ed18c59..e31d0f5 100644

--- a/migration/migration.c

+++ b/migration/migration.c

@@ -3253,6 +3253,37 @@ void migration_consume_urgent_request(void)

     qemu_sem_wait(&migrate_get_current()->rate_limit_sem);

 }

+/* Returns true if the rate limiting was broken by an urgent request */

+bool migration_rate_limit(void)

+{

+    int64_t now = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);

+    MigrationState *s = migrate_get_current();

+

+    bool urgent = false;

+    migration_update_counters(s, now);

+    if (qemu_file_rate_limit(s->to_dst_file)) {

+        /*

+         * Wait for a delay to do rate limiting OR

+         * something urgent to post the semaphore.

+         */

+        int ms = s->iteration_start_time + BUFFER_DELAY - now;

+        trace_migration_rate_limit_pre(ms);

+        if (qemu_sem_timedwait(&s->rate_limit_sem, ms) == 0) {

+            /*

+             * We were woken by one or more urgent things but

+             * the timedwait will have consumed one of them.

+             * The service routine for the urgent wake will dec

+             * the semaphore itself for each item it consumes,

+             * so add this one we just eat back.

+             */

+            qemu_sem_post(&s->rate_limit_sem);

+            urgent = true;

+        }

+        trace_migration_rate_limit_post(urgent);

+    }

+    return urgent;

+}

+

 /*

  * Master migration thread on the source VM.

  * It drives the migration and pumps the data down the outgoing channel.

@@ -3319,8 +3350,6 @@ static void *migration_thread(void *opaque)

     trace_migration_thread_setup_complete();

     while (migration_is_active(s)) {

-        int64_t current_time;

-

         if (urgent || !qemu_file_rate_limit(s->to_dst_file)) {

             MigIterateState iter_state = migration_iteration_run(s);

             if (iter_state == MIG_ITERATE_SKIP) {

@@ -3347,29 +3376,7 @@ static void *migration_thread(void *opaque)

             update_iteration_initial_status(s);

         }

-        current_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);

-

-        migration_update_counters(s, current_time);

-

-        urgent = false;

-        if (qemu_file_rate_limit(s->to_dst_file)) {

-            /* Wait for a delay to do rate limiting OR

-             * something urgent to post the semaphore.

-             */

-            int ms = s->iteration_start_time + BUFFER_DELAY - current_time;

-            trace_migration_thread_ratelimit_pre(ms);

-            if (qemu_sem_timedwait(&s->rate_limit_sem, ms) == 0) {

-                /* We were worken by one or more urgent things but

-                 * the timedwait will have consumed one of them.

-                 * The service routine for the urgent wake will dec

-                 * the semaphore itself for each item it consumes,

-                 * so add this one we just eat back.

-                 */

-                qemu_sem_post(&s->rate_limit_sem);

-                urgent = true;

-            }

-            trace_migration_thread_ratelimit_post(urgent);

-        }

+        urgent = migration_rate_limit();

     }

     trace_migration_thread_after_loop();

diff --git a/migration/migration.h b/migration/migration.h

index a2b2336..a15e8d8 100644

--- a/migration/migration.h

+++ b/migration/migration.h

@@ -347,5 +347,6 @@ extern bool migrate_pre_2_2;

 void migration_make_urgent_request(void);

 void migration_consume_urgent_request(void);

+bool migration_rate_limit(void);

 #endif

diff --git a/migration/ram.c b/migration/ram.c

index 3891eff..5344c7d 100644

--- a/migration/ram.c

+++ b/migration/ram.c

@@ -2661,6 +2661,8 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss,

         pages += tmppages;

         pss->page++;

+        /* Allow rate limiting to happen in the middle of huge pages */

+        migration_rate_limit();

     } while ((pss->page & (pagesize_bits - 1)) &&

              offset_in_ramblock(pss->block, pss->page << TARGET_PAGE_BITS));

diff --git a/migration/trace-events b/migration/trace-events

index 6dee7b5..2f9129e 100644

--- a/migration/trace-events

+++ b/migration/trace-events

@@ -138,12 +138,12 @@ migrate_send_rp_recv_bitmap(char *name, int64_t size) "block '%s' size 0x%"PRIi6

 migration_completion_file_err(void) ""

 migration_completion_postcopy_end(void) ""

 migration_completion_postcopy_end_after_complete(void) ""

+migration_rate_limit_pre(int ms) "%d ms"

+migration_rate_limit_post(int urgent) "urgent: %d"

 migration_return_path_end_before(void) ""

 migration_return_path_end_after(int rp_error) "%d"

 migration_thread_after_loop(void) ""

 migration_thread_file_err(void) ""

-migration_thread_ratelimit_pre(int ms) "%d ms"

-migration_thread_ratelimit_post(int urgent) "urgent: %d"

 migration_thread_setup_complete(void) ""

 open_return_path_on_source(void) ""

 open_return_path_on_source_continue(void) ""

-- 

1.8.3.1