From 10238fad0389175f71739bc9b4d00bb24d9b8c44 Mon Sep 17 00:00:00 2001
From: Magnus Hagander <magnus@hagander.net>
Date: Mon, 19 Dec 2016 10:11:04 +0100
Subject: [PATCH] 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 ffc7e586dba..40b3c117e8f 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -1370,26 +1370,16 @@ 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();
}
--
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