Commit 97e1e067 authored by Dr. David Alan Gilbert's avatar Dr. David Alan Gilbert Committed by Juan Quintela
Browse files

migration: Rate limit inside host pages 



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: 4c011c37 ("postcopy: Send whole huge pages")
Reported-by: default avatarLin Ma <LMa@suse.com>
Signed-off-by: default avatarDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: default avatarJuan Quintela <quintela@redhat.com>
Reviewed-by: default avatarPeter Xu <peterx@redhat.com>
Signed-off-by: default avatarJuan Quintela <quintela@redhat.com>
parent 03acb4e9

migration/migration.c

+32 −25
Original line number Diff line number Diff line
@@ -3224,6 +3224,37 @@ 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.
@@ -3290,8 +3321,6 @@ 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) {
@@ -3318,29 +3347,7 @@ 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();

migration/migration.h

+1 −0
Original line number Diff line number Diff line
@@ -341,5 +341,6 @@ int foreach_not_ignored_block(RAMBlockIterFunc func, void *opaque); 


void migration_make_urgent_request(void);

void migration_consume_urgent_request(void);

bool migration_rate_limit(void);



#endif

migration/ram.c

+2 −0
Original line number Diff line number Diff line
@@ -2639,6 +2639,8 @@ 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));

migration/trace-events

+2 −2
Original line number Diff line number Diff line
@@ -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) ""