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Reduce idle power consumption of walwriter and checkpointer processes.

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This patch modifies the walwriter process so that, when it has not found
anything useful to do for many consecutive wakeup cycles, it extends its
sleep time to reduce the server's idle power consumption.  It reverts to
normal as soon as it's done any successful flushes.  It's still true that
during any async commit, backends check for completed, unflushed pages of
WAL and signal the walwriter if there are any; so that in practice the
walwriter can get awakened and returned to normal operation sooner than the
sleep time might suggest.

Also, improve the checkpointer so that it uses a latch and a computed delay
time to not wake up at all except when it has something to do, replacing a
previous hardcoded 0.5 sec wakeup cycle.  This also is primarily useful for
reducing the server's power consumption when idle.

In passing, get rid of the dedicated latch for signaling the walwriter in
favor of using its procLatch, since that comports better with possible
generic signal handlers using that latch.  Also, fix a pre-existing bug
with failure to save/restore errno in walwriter's signal handlers.

Peter Geoghegan, somewhat simplified by Tom
This commit is contained in:
Tom Lane
2012-05-08 20:03:26 -04:00
parent 081ca7a0d1
commit 5461564a9d
7 changed files with 189 additions and 59 deletions
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4
src/include/access/xlog.h
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@ -16,7 +16,6 @@
#include "datatype/timestamp.h"
#include "lib/stringinfo.h"
#include "storage/buf.h"
#include "storage/latch.h"
#include "utils/pg_crc.h"
/*
@ -266,7 +265,7 @@ extern CheckpointStatsData CheckpointStats;
extern XLogRecPtr XLogInsert(RmgrId rmid, uint8 info, XLogRecData *rdata);
extern void XLogFlush(XLogRecPtr RecPtr);
extern void XLogBackgroundFlush(void);
extern bool XLogBackgroundFlush(void);
extern bool XLogNeedsFlush(XLogRecPtr RecPtr);
extern int XLogFileInit(uint32 log, uint32 seg,
bool *use_existent, bool use_lock);
@ -317,7 +316,6 @@ extern TimeLineID GetRecoveryTargetTLI(void);
extern bool CheckPromoteSignal(void);
extern void WakeupRecovery(void);
extern Latch *WALWriterLatch(void);
/*
* Starting/stopping a base backup