From 2d46a57ddcad394e514bbefb193a4a03e766f163 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Sat, 21 Jul 2012 20:10:29 -0400 Subject: [PATCH] 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 as well save the kernel calls; (b) at least on Linux we know that the kernel might block us until it's scheduled the write. Also, avoid making a useless second traversal of the directory tree if we're not actually going to call fsync(2) after all. --- src/backend/storage/file/copydir.c | 8 ++++++-- src/backend/storage/file/fd.c | 14 +++++++++----- 2 files changed, 15 insertions(+), 7 deletions(-) diff --git a/src/backend/storage/file/copydir.c b/src/backend/storage/file/copydir.c index dc89442041..cf47708a79 100644 --- a/src/backend/storage/file/copydir.c +++ b/src/backend/storage/file/copydir.c @@ -98,7 +98,11 @@ copydir(char *fromdir, char *todir, bool recurse) /* * Be paranoid here and fsync all files to ensure the copy is really done. + * But if fsync is disabled, we're done. */ + if (!enableFsync) + return; + xldir = AllocateDir(todir); if (xldir == NULL) ereport(ERROR, @@ -200,9 +204,9 @@ copy_file(char *fromfile, char *tofile) /* * We fsync the files later but first flush them to avoid spamming the * cache and hopefully get the kernel to start writing them out before - * the fsync comes. + * the fsync comes. Ignore any error, since it's only a hint. */ - pg_flush_data(dstfd, offset, nbytes); + (void) pg_flush_data(dstfd, offset, nbytes); } if (close(dstfd)) diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c index 9724f481dc..1e54715056 100644 --- a/src/backend/storage/file/fd.c +++ b/src/backend/storage/file/fd.c @@ -337,18 +337,22 @@ pg_fdatasync(int fd) * pg_flush_data --- advise OS that the data described won't be needed soon * * Not all platforms have sync_file_range or posix_fadvise; treat as no-op - * if not available. + * if not available. Also, treat as no-op if enableFsync is off; this is + * because the call isn't free, and some platforms such as Linux will actually + * block the requestor until the write is scheduled. */ int pg_flush_data(int fd, off_t offset, off_t amount) { + if (enableFsync) + { #if defined(HAVE_SYNC_FILE_RANGE) - return sync_file_range(fd, offset, amount, SYNC_FILE_RANGE_WRITE); + return sync_file_range(fd, offset, amount, SYNC_FILE_RANGE_WRITE); #elif defined(USE_POSIX_FADVISE) && defined(POSIX_FADV_DONTNEED) - return posix_fadvise(fd, offset, amount, POSIX_FADV_DONTNEED); -#else - return 0; + return posix_fadvise(fd, offset, amount, POSIX_FADV_DONTNEED); #endif + } + return 0; } -- 2.40.0