postgres.git / summary / log / commit / refs

commit    bc53d71308a2b4bd8216932fda3e21cec4915ff8
Author:   Magnus Hagander <magnus@hagander.net>
Date:     Mon Dec 19 09:11:04 2016 +0000

    Fix base backup rate limiting in presence of slow i/o
    
    When source i/o on disk was too slow compared to the rate limiting
    specified, the system could end up with a negative value for sleep that
    it never got out of, which caused rate limiting to effectively be
    turned off.
    
    Discussion: https://postgr.es/m/CABUevEy_-e0YvL4ayoX8bH_Ja9w%2BBHoP6jUgdxZuG2nEj3uAfQ%40mail.gmail.com
    
    Analysis by me, patch by Antonin Houska


 src/backend/replication/basebackup.c | 24 +++++++-----------------
 1 file changed, 7 insertions(+), 17 deletions(-)

diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index 901a65c51ca..624dea3b03a 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -1300,26 +1300,16 @@ throttle(size_t increment)
 		if (wait_result & WL_LATCH_SET)
 			CHECK_FOR_INTERRUPTS();
 	}
-	else
-	{
-		/*
-		 * The actual transfer rate is below the limit.  A negative value
-		 * would distort the adjustment of throttled_last.
-		 */
-		wait_result = 0;
-		sleep = 0;
-	}
 
 	/*
-	 * Only a whole multiple of throttling_sample was processed. The rest will
-	 * be done during the next call of this function.
+	 * As we work with integers, only whole multiple of throttling_sample was
+	 * processed. The rest will be done during the next call of this function.
 	 */
 	throttling_counter %= throttling_sample;
 
-	/* Once the (possible) sleep has ended, new period starts. */
-	if (wait_result & WL_TIMEOUT)
-		throttled_last += elapsed + sleep;
-	else if (sleep > 0)
-		/* Sleep was necessary but might have been interrupted. */
-		throttled_last = GetCurrentIntegerTimestamp();
+	/*
+	 * Time interval for the remaining amount and possible next increments
+	 * starts now.
+	 */
+	throttled_last = GetCurrentIntegerTimestamp();
 }


[parent: 53140bf22bc4]