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From 8e8f421cce99543081f225acf46541312cfbc371 Mon Sep 17 00:00:00 2001
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From: Laurent Vivier <lvivier@redhat.com>
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Date: Tue, 17 Mar 2020 17:05:18 +0000
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Subject: [PATCH 1/2] migration: Rate limit inside host pages
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RH-Author: Laurent Vivier <lvivier@redhat.com>
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Message-id: <20200317170518.9303-1-lvivier@redhat.com>
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Patchwork-id: 94374
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O-Subject: [RHEL-AV-8.2.0 qemu-kvm PATCH] migration: Rate limit inside host pages
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Bugzilla: 1814336
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RH-Acked-by: Peter Xu <peterx@redhat.com>
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RH-Acked-by: Juan Quintela <quintela@redhat.com>
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RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
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When using hugepages, rate limiting is necessary within each huge
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page, since a 1G huge page can take a significant time to send, so
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you end up with bursty behaviour.
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Fixes: 4c011c37ecb3 ("postcopy: Send whole huge pages")
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Reported-by: Lin Ma <LMa@suse.com>
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Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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Reviewed-by: Juan Quintela <quintela@redhat.com>
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Reviewed-by: Peter Xu <peterx@redhat.com>
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Signed-off-by: Juan Quintela <quintela@redhat.com>
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(cherry picked from commit 97e1e06780e70f6e98a0d2df881e0c0927d3aeb6)
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Signed-off-by: Laurent Vivier <lvivier@redhat.com>
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BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1814336
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BRANCH: rhel-av-8.2.0
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UPSTREAM: Merged
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BREW: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=27283241
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TESTED: Tested that the migration abort doesn't trigger an error message in
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        the kernel logs on P9
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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 migration/migration.c  | 57 ++++++++++++++++++++++++++++----------------------
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 migration/migration.h  |  1 +
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 migration/ram.c        |  2 ++
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 migration/trace-events |  4 ++--
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 4 files changed, 37 insertions(+), 27 deletions(-)
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diff --git a/migration/migration.c b/migration/migration.c
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index ed18c59..e31d0f5 100644
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--- a/migration/migration.c
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+++ b/migration/migration.c
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@@ -3253,6 +3253,37 @@ void migration_consume_urgent_request(void)
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     qemu_sem_wait(&migrate_get_current()->rate_limit_sem);
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 }
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+/* Returns true if the rate limiting was broken by an urgent request */
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+bool migration_rate_limit(void)
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+{
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+    int64_t now = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
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+    MigrationState *s = migrate_get_current();
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+
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+    bool urgent = false;
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+    migration_update_counters(s, now);
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+    if (qemu_file_rate_limit(s->to_dst_file)) {
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+        /*
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+         * Wait for a delay to do rate limiting OR
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+         * something urgent to post the semaphore.
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+         */
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+        int ms = s->iteration_start_time + BUFFER_DELAY - now;
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+        trace_migration_rate_limit_pre(ms);
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+        if (qemu_sem_timedwait(&s->rate_limit_sem, ms) == 0) {
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+            /*
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+             * We were woken by one or more urgent things but
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+             * the timedwait will have consumed one of them.
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+             * The service routine for the urgent wake will dec
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+             * the semaphore itself for each item it consumes,
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+             * so add this one we just eat back.
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+             */
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+            qemu_sem_post(&s->rate_limit_sem);
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+            urgent = true;
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+        }
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+        trace_migration_rate_limit_post(urgent);
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+    }
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+    return urgent;
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+}
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+
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 /*
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  * Master migration thread on the source VM.
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  * It drives the migration and pumps the data down the outgoing channel.
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@@ -3319,8 +3350,6 @@ static void *migration_thread(void *opaque)
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     trace_migration_thread_setup_complete();
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     while (migration_is_active(s)) {
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-        int64_t current_time;
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-
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         if (urgent || !qemu_file_rate_limit(s->to_dst_file)) {
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             MigIterateState iter_state = migration_iteration_run(s);
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             if (iter_state == MIG_ITERATE_SKIP) {
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@@ -3347,29 +3376,7 @@ static void *migration_thread(void *opaque)
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             update_iteration_initial_status(s);
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         }
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-        current_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
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-
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-        migration_update_counters(s, current_time);
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-
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-        urgent = false;
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-        if (qemu_file_rate_limit(s->to_dst_file)) {
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-            /* Wait for a delay to do rate limiting OR
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-             * something urgent to post the semaphore.
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-             */
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-            int ms = s->iteration_start_time + BUFFER_DELAY - current_time;
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-            trace_migration_thread_ratelimit_pre(ms);
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-            if (qemu_sem_timedwait(&s->rate_limit_sem, ms) == 0) {
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-                /* We were worken by one or more urgent things but
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-                 * the timedwait will have consumed one of them.
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-                 * The service routine for the urgent wake will dec
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-                 * the semaphore itself for each item it consumes,
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-                 * so add this one we just eat back.
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-                 */
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-                qemu_sem_post(&s->rate_limit_sem);
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-                urgent = true;
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-            }
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-            trace_migration_thread_ratelimit_post(urgent);
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-        }
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+        urgent = migration_rate_limit();
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     }
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     trace_migration_thread_after_loop();
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diff --git a/migration/migration.h b/migration/migration.h
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index a2b2336..a15e8d8 100644
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--- a/migration/migration.h
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+++ b/migration/migration.h
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@@ -347,5 +347,6 @@ extern bool migrate_pre_2_2;
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 void migration_make_urgent_request(void);
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 void migration_consume_urgent_request(void);
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+bool migration_rate_limit(void);
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 #endif
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diff --git a/migration/ram.c b/migration/ram.c
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index 3891eff..5344c7d 100644
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--- a/migration/ram.c
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+++ b/migration/ram.c
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@@ -2661,6 +2661,8 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss,
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         pages += tmppages;
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         pss->page++;
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+        /* Allow rate limiting to happen in the middle of huge pages */
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+        migration_rate_limit();
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     } while ((pss->page & (pagesize_bits - 1)) &&
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              offset_in_ramblock(pss->block, pss->page << TARGET_PAGE_BITS));
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diff --git a/migration/trace-events b/migration/trace-events
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index 6dee7b5..2f9129e 100644
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--- a/migration/trace-events
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+++ b/migration/trace-events
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@@ -138,12 +138,12 @@ migrate_send_rp_recv_bitmap(char *name, int64_t size) "block '%s' size 0x%"PRIi6
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 migration_completion_file_err(void) ""
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 migration_completion_postcopy_end(void) ""
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 migration_completion_postcopy_end_after_complete(void) ""
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+migration_rate_limit_pre(int ms) "%d ms"
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+migration_rate_limit_post(int urgent) "urgent: %d"
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 migration_return_path_end_before(void) ""
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 migration_return_path_end_after(int rp_error) "%d"
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 migration_thread_after_loop(void) ""
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 migration_thread_file_err(void) ""
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-migration_thread_ratelimit_pre(int ms) "%d ms"
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-migration_thread_ratelimit_post(int urgent) "urgent: %d"
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 migration_thread_setup_complete(void) ""
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 open_return_path_on_source(void) ""
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 open_return_path_on_source_continue(void) ""
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-- 
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1.8.3.1
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