Commit10238fa

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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
`@@ -1370,26 +1370,16 @@ throttle(size_t increment)`
`1370`	`1370`	`if (wait_result&WL_LATCH_SET)`
`1371`	`1371`	`CHECK_FOR_INTERRUPTS();`
`1372`	`1372`	`}`
`1373`		`-else`
`1374`		`-{`
`1375`		`-/*`
`1376`		`- * The actual transfer rate is below the limit. A negative value`
`1377`		`- * would distort the adjustment of throttled_last.`
`1378`		`- */`
`1379`		`-wait_result=0;`
`1380`		`-sleep=0;`
`1381`		`-}`
`1382`	`1373`
`1383`	`1374`	`/*`
`1384`		`- *Only awhole multiple of throttling_sample was processed. The rest will`
`1385`		`- * be done during the next call of this function.`
	`1375`	`+ *As we work with integers, onlywhole multiple of throttling_sample was`
	`1376`	`+ *processed. The rest willbe done during the next call of this function.`
`1386`	`1377`	`*/`
`1387`	`1378`	`throttling_counter %=throttling_sample;`
`1388`	`1379`
`1389`		`-/* Once the (possible) sleep has ended, new period starts. */`
`1390`		`-if (wait_result&WL_TIMEOUT)`
`1391`		`-throttled_last+=elapsed+sleep;`
`1392`		`-elseif (sleep>0)`
`1393`		`-/* Sleep was necessary but might have been interrupted. */`
`1394`		`-throttled_last=GetCurrentIntegerTimestamp();`
	`1380`	`+/*`
	`1381`	`+ * Time interval for the remaining amount and possible next increments`
	`1382`	`+ * starts now.`
	`1383`	`+ */`
	`1384`	`+throttled_last=GetCurrentIntegerTimestamp();`
`1395`	`1385`	`}`

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