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Allow BASE_BACKUP to be throttled
A new MAX_RATE option allows imposing a limit to the network transfer rate from the server side. This is useful to limit the stress that taking a base backup has on the server. pg_basebackup is now able to specify a value to the server, too. Author: Antonin Houska Patch reviewed by Stefan Radomski, Andres Freund, Zoltán Böszörményi, Fujii Masao, and Álvaro Herrera.
This commit is contained in:
Alvaro Herrera
@ -25,6 +25,7 @@
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#include "libpq/pqformat.h"
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#include "miscadmin.h"
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#include "nodes/pg_list.h"
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#include "pgtar.h"
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#include "pgstat.h"
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#include "replication/basebackup.h"
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#include "replication/walsender.h"
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@ -34,7 +35,8 @@
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#include "utils/builtins.h"
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#include "utils/elog.h"
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#include "utils/ps_status.h"
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#include "pgtar.h"
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#include "utils/timestamp.h"
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typedef struct
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{
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@ -43,6 +45,7 @@ typedef struct
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bool fastcheckpoint;
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bool nowait;
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bool includewal;
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uint32 maxrate;
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} basebackup_options;
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@ -60,6 +63,7 @@ static void perform_base_backup(basebackup_options *opt, DIR *tblspcdir);
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static void parse_basebackup_options(List *options, basebackup_options *opt);
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static void SendXlogRecPtrResult(XLogRecPtr ptr, TimeLineID tli);
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static int compareWalFileNames(const void *a, const void *b);
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static void throttle(size_t increment);
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/* Was the backup currently in-progress initiated in recovery mode? */
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static bool backup_started_in_recovery = false;
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@ -72,6 +76,23 @@ static char *statrelpath = NULL;
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*/
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#define TAR_SEND_SIZE 32768
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/*
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* How frequently to throttle, as a fraction of the specified rate-second.
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*/
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#define THROTTLING_FREQUENCY 8
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/* The actual number of bytes, transfer of which may cause sleep. */
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static uint64 throttling_sample;
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/* Amount of data already transfered but not yet throttled. */
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static int64 throttling_counter;
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/* The minimum time required to transfer throttling_sample bytes. */
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static int64 elapsed_min_unit;
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/* The last check of the transfer rate. */
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static int64 throttled_last;
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typedef struct
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{
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char *oid;
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@ -203,6 +224,29 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
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/* Send tablespace header */
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SendBackupHeader(tablespaces);
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/* Setup and activate network throttling, if client requested it */
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if (opt->maxrate > 0)
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{
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throttling_sample = opt->maxrate * 1024 / THROTTLING_FREQUENCY;
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/*
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* The minimum amount of time for throttling_sample
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* bytes to be transfered.
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*/
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elapsed_min_unit = USECS_PER_SEC / THROTTLING_FREQUENCY;
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/* Enable throttling. */
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throttling_counter = 0;
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/* The 'real data' starts now (header was ignored). */
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throttled_last = GetCurrentIntegerTimestamp();
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}
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else
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{
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/* Disable throttling. */
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throttling_counter = -1;
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}
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/* Send off our tablespaces one by one */
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foreach(lc, tablespaces)
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{
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@ -430,6 +474,8 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
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(errmsg("base backup could not send data, aborting backup")));
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len += cnt;
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throttle(cnt);
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if (len == XLogSegSize)
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break;
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}
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@ -500,6 +546,7 @@ parse_basebackup_options(List *options, basebackup_options *opt)
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bool o_fast = false;
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bool o_nowait = false;
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bool o_wal = false;
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bool o_maxrate = false;
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MemSet(opt, 0, sizeof(*opt));
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foreach(lopt, options)
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@ -551,6 +598,25 @@ parse_basebackup_options(List *options, basebackup_options *opt)
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opt->includewal = true;
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o_wal = true;
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}
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else if (strcmp(defel->defname, "max_rate") == 0)
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{
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long maxrate;
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if (o_maxrate)
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ereport(ERROR,
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(errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("duplicate option \"%s\"", defel->defname)));
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maxrate = intVal(defel->arg);
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if (maxrate < MAX_RATE_LOWER || maxrate > MAX_RATE_UPPER)
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ereport(ERROR,
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(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
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errmsg("%d is outside the valid range for parameter \"%s\" (%d .. %d)",
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(int) maxrate, "MAX_RATE", MAX_RATE_LOWER, MAX_RATE_UPPER)));
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opt->maxrate = (uint32) maxrate;
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o_maxrate = true;
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}
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else
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elog(ERROR, "option \"%s\" not recognized",
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defel->defname);
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@ -1112,6 +1178,7 @@ sendFile(char *readfilename, char *tarfilename, struct stat * statbuf,
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(errmsg("base backup could not send data, aborting backup")));
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len += cnt;
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throttle(cnt);
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if (len >= statbuf->st_size)
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{
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@ -1133,10 +1200,14 @@ sendFile(char *readfilename, char *tarfilename, struct stat * statbuf,
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cnt = Min(sizeof(buf), statbuf->st_size - len);
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pq_putmessage('d', buf, cnt);
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len += cnt;
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throttle(cnt);
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}
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}
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/* Pad to 512 byte boundary, per tar format requirements */
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/*
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* Pad to 512 byte boundary, per tar format requirements. (This small
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* piece of data is probably not worth throttling.)
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*/
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pad = ((len + 511) & ~511) - len;
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if (pad > 0)
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{
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@ -1162,3 +1233,65 @@ _tarWriteHeader(const char *filename, const char *linktarget,
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pq_putmessage('d', h, 512);
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}
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/*
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* Increment the network transfer counter by the given number of bytes,
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* and sleep if necessary to comply with the requested network transfer
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* rate.
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*/
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static void
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throttle(size_t increment)
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{
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int64 elapsed,
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elapsed_min,
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sleep;
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int wait_result;
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if (throttling_counter < 0)
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return;
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throttling_counter += increment;
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if (throttling_counter < throttling_sample)
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return;
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/* Time elapsed since the last measurement (and possible wake up). */
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elapsed = GetCurrentIntegerTimestamp() - throttled_last;
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/* How much should have elapsed at minimum? */
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elapsed_min = elapsed_min_unit * (throttling_counter / throttling_sample);
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sleep = elapsed_min - elapsed;
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/* Only sleep if the transfer is faster than it should be. */
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if (sleep > 0)
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{
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ResetLatch(&MyWalSnd->latch);
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/*
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* (TAR_SEND_SIZE / throttling_sample * elapsed_min_unit) should be
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* the maximum time to sleep. Thus the cast to long is safe.
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*/
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wait_result = WaitLatch(&MyWalSnd->latch,
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WL_LATCH_SET | WL_TIMEOUT | WL_POSTMASTER_DEATH,
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(long) (sleep / 1000));
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}
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else
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{
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/*
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* The actual transfer rate is below the limit. A negative value would
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* distort the adjustment of throttled_last.
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*/
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wait_result = 0;
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sleep = 0;
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}
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/*
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* Only a whole multiple of throttling_sample was processed. The rest will
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* be done during the next call of this function.
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*/
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throttling_counter %= throttling_sample;
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/* Once the (possible) sleep has ended, new period starts. */
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if (wait_result & WL_TIMEOUT)
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throttled_last += elapsed + sleep;
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else if (sleep > 0)
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/* Sleep was necessary but might have been interrupted. */
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throttled_last = GetCurrentIntegerTimestamp();
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}
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