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Commit2d46a57

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Improve copydir() code for the case that fsync is off.
We should avoid calling sync_file_range or posix_fadvise in this case,since (a) we don't really care if the data gets synced, and might aswell save the kernel calls; (b) at least on Linux we know that thekernel might block us until it's scheduled the write.Also, avoid making a useless second traversal of the directory treeif we're not actually going to call fsync(2) after all.
1 parent2c4f5b4 commit2d46a57

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2 files changed

+15
-7
lines changed

2 files changed

+15
-7
lines changed

‎src/backend/storage/file/copydir.c

Lines changed: 6 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -98,7 +98,11 @@ copydir(char *fromdir, char *todir, bool recurse)
9898

9999
/*
100100
* Be paranoid here and fsync all files to ensure the copy is really done.
101+
* But if fsync is disabled, we're done.
101102
*/
103+
if (!enableFsync)
104+
return;
105+
102106
xldir=AllocateDir(todir);
103107
if (xldir==NULL)
104108
ereport(ERROR,
@@ -200,9 +204,9 @@ copy_file(char *fromfile, char *tofile)
200204
/*
201205
* We fsync the files later but first flush them to avoid spamming the
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* cache and hopefully get the kernel to start writing them out before
203-
* the fsync comes.
207+
* the fsync comes. Ignore any error, since it's only a hint.
204208
*/
205-
pg_flush_data(dstfd,offset,nbytes);
209+
(void)pg_flush_data(dstfd,offset,nbytes);
206210
}
207211

208212
if (close(dstfd))

‎src/backend/storage/file/fd.c

Lines changed: 9 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -337,18 +337,22 @@ pg_fdatasync(int fd)
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* pg_flush_data --- advise OS that the data described won't be needed soon
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*
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* Not all platforms have sync_file_range or posix_fadvise; treat as no-op
340-
* if not available.
340+
* if not available. Also, treat as no-op if enableFsync is off; this is
341+
* because the call isn't free, and some platforms such as Linux will actually
342+
* block the requestor until the write is scheduled.
341343
*/
342344
int
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pg_flush_data(intfd,off_toffset,off_tamount)
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{
347+
if (enableFsync)
348+
{
345349
#if defined(HAVE_SYNC_FILE_RANGE)
346-
returnsync_file_range(fd,offset,amount,SYNC_FILE_RANGE_WRITE);
350+
returnsync_file_range(fd,offset,amount,SYNC_FILE_RANGE_WRITE);
347351
#elif defined(USE_POSIX_FADVISE)&& defined(POSIX_FADV_DONTNEED)
348-
returnposix_fadvise(fd,offset,amount,POSIX_FADV_DONTNEED);
349-
#else
350-
return0;
352+
returnposix_fadvise(fd,offset,amount,POSIX_FADV_DONTNEED);
351353
#endif
354+
}
355+
return0;
352356
}
353357

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