Commit1c8ad59

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Fix base backup rate limiting in presence of slow i/o

When source i/o on disk was too slow compared to the rate limitingspecified, the system could end up with a negative value for sleep thatit never got out of, which caused rate limiting to effectively beturned off.Discussion:https://postgr.es/m/CABUevEy_-e0YvL4ayoX8bH_Ja9w%2BBHoP6jUgdxZuG2nEj3uAfQ%40mail.gmail.comAnalysis by me, patch by Antonin Houska

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Lines changed: 7 additions & 17 deletions

Original file line number	Diff line number	Diff line change
`@@ -1303,26 +1303,16 @@ throttle(size_t increment)`
`1303`	`1303`	`if (wait_result&WL_LATCH_SET)`
`1304`	`1304`	`CHECK_FOR_INTERRUPTS();`
`1305`	`1305`	`}`
`1306`		`-else`
`1307`		`-{`
`1308`		`-/*`
`1309`		`- * The actual transfer rate is below the limit. A negative value`
`1310`		`- * would distort the adjustment of throttled_last.`
`1311`		`- */`
`1312`		`-wait_result=0;`
`1313`		`-sleep=0;`
`1314`		`-}`
`1315`	`1306`
`1316`	`1307`	`/*`
`1317`		`- *Only awhole multiple of throttling_sample was processed. The rest will`
`1318`		`- * be done during the next call of this function.`
	`1308`	`+ *As we work with integers, onlywhole multiple of throttling_sample was`
	`1309`	`+ *processed. The rest willbe done during the next call of this function.`
`1319`	`1310`	`*/`
`1320`	`1311`	`throttling_counter %=throttling_sample;`
`1321`	`1312`
`1322`		`-/* Once the (possible) sleep has ended, new period starts. */`
`1323`		`-if (wait_result&WL_TIMEOUT)`
`1324`		`-throttled_last+=elapsed+sleep;`
`1325`		`-elseif (sleep>0)`
`1326`		`-/* Sleep was necessary but might have been interrupted. */`
`1327`		`-throttled_last=GetCurrentIntegerTimestamp();`
	`1313`	`+/*`
	`1314`	`+ * Time interval for the remaining amount and possible next increments`
	`1315`	`+ * starts now.`
	`1316`	`+ */`
	`1317`	`+throttled_last=GetCurrentIntegerTimestamp();`
`1328`	`1318`	`}`

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