From f8c183a1ac02aef14832c1f29946ef2bcb5866b7 Mon Sep 17 00:00:00 2001
From: Greg Stark <stark@mit.edu>
Date: Mon, 15 Feb 2010 00:50:57 +0000
Subject: [PATCH] Speed up CREATE DATABASE by deferring the fsyncs until after
copying all the data and using posix_fadvise to nudge the OS into flushing it
earlier. This also hopefully makes CREATE DATABASE avoid spamming the cache.
Tests show a big speedup on Linux at least on some filesystems.
Idea and patch from Andres Freund.
---
src/backend/storage/file/fd.c | 18 +++++++-
src/include/storage/fd.h | 3 +-
src/port/copydir.c | 84 ++++++++++++++++++++++++-----------
3 files changed, 76 insertions(+), 29 deletions(-)
diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index ec27859e606..adea849ab05 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/storage/file/fd.c,v 1.153 2010/01/12 02:42:52 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/storage/file/fd.c,v 1.154 2010/02/15 00:50:57 stark Exp $
*
* NOTES:
*
@@ -319,6 +319,22 @@ pg_fdatasync(int fd)
return 0;
}
+/*
+ * pg_flush_data --- advise OS that the data described won't be needed soon
+ *
+ * Not all platforms have posix_fadvise; treat as noop if not available.
+ */
+int
+pg_flush_data(int fd, off_t offset, off_t amount)
+{
+#if defined(USE_POSIX_FADVISE) && defined(POSIX_FADV_DONTNEED)
+ return posix_fadvise(fd, offset, amount, POSIX_FADV_DONTNEED);
+#else
+ return 0;
+#endif
+}
+
+
/*
* InitFileAccess --- initialize this module during backend startup
*
diff --git a/src/include/storage/fd.h b/src/include/storage/fd.h
index 20f60918afb..9dd240e34cf 100644
--- a/src/include/storage/fd.h
+++ b/src/include/storage/fd.h
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/storage/fd.h,v 1.66 2010/01/02 16:58:08 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/storage/fd.h,v 1.67 2010/02/15 00:50:57 stark Exp $
*
*-------------------------------------------------------------------------
*/
@@ -98,6 +98,7 @@ extern int pg_fsync(int fd);
extern int pg_fsync_no_writethrough(int fd);
extern int pg_fsync_writethrough(int fd);
extern int pg_fdatasync(int fd);
+extern int pg_flush_data(int fd, off_t offset, off_t amount);
/* Filename components for OpenTemporaryFile */
#define PG_TEMP_FILES_DIR "pgsql_tmp"
diff --git a/src/port/copydir.c b/src/port/copydir.c
index 0bf764ecffc..a52b1f71a1b 100644
--- a/src/port/copydir.c
+++ b/src/port/copydir.c
@@ -11,7 +11,7 @@
* as a service.
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/port/copydir.c,v 1.25 2010/02/14 17:50:52 stark Exp $
+ * $PostgreSQL: pgsql/src/port/copydir.c,v 1.26 2010/02/15 00:50:57 stark Exp $
*
*-------------------------------------------------------------------------
*/
@@ -37,6 +37,7 @@
static void copy_file(char *fromfile, char *tofile);
+static void fsync_fname(char *fname);
/*
@@ -91,27 +92,32 @@ copydir(char *fromdir, char *todir, bool recurse)
copy_file(fromfile, tofile);
}
- FreeDir(xldir);
-
/*
- * fsync the directory to make sure not just the data but also the
- * new directory file entries have reached the disk. While needed
- * by most filesystems, the window got bigger with newer ones like
- * ext4.
+ * Be paranoid here and fsync all files to ensure we catch problems.
*/
- dirfd = BasicOpenFile(todir,
- O_RDONLY | PG_BINARY,
- S_IRUSR | S_IWUSR);
- if(dirfd == -1)
- ereport(ERROR,
- (errcode_for_file_access(),
- errmsg("could not open directory for fsync \"%s\": %m", todir)));
-
- if(pg_fsync(dirfd) == -1)
+ if (xldir == NULL)
ereport(ERROR,
(errcode_for_file_access(),
- errmsg("could not fsync directory \"%s\": %m", todir)));
- close(dirfd);
+ errmsg("could not open directory \"%s\": %m", fromdir)));
+
+ while ((xlde = ReadDir(xldir, fromdir)) != NULL)
+ {
+ if (strcmp(xlde->d_name, ".") == 0 ||
+ strcmp(xlde->d_name, "..") == 0)
+ continue;
+
+ snprintf(tofile, MAXPGPATH, "%s/%s", todir, xlde->d_name);
+ fsync_fname(tofile);
+ }
+ FreeDir(xldir);
+
+ /* It's important to fsync the destination directory itself as
+ * individual file fsyncs don't guarantee that the directory entry
+ * for the file is synced. Recent versions of ext4 have made the
+ * window much wider but it's been true for ext3 and other
+ * filesyetems in the past
+ */
+ fsync_fname(todir);
}
/*
@@ -124,6 +130,7 @@ copy_file(char *fromfile, char *tofile)
int srcfd;
int dstfd;
int nbytes;
+ off_t offset;
/* Use palloc to ensure we get a maxaligned buffer */
#define COPY_BUF_SIZE (8 * BLCKSZ)
@@ -149,7 +156,7 @@ copy_file(char *fromfile, char *tofile)
/*
* Do the data copying.
*/
- for (;;)
+ for (offset=0; ; offset+=nbytes)
{
nbytes = read(srcfd, buffer, COPY_BUF_SIZE);
if (nbytes < 0)
@@ -168,15 +175,14 @@ copy_file(char *fromfile, char *tofile)
(errcode_for_file_access(),
errmsg("could not write to file \"%s\": %m", tofile)));
}
- }
- /*
- * Be paranoid here to ensure we catch problems.
- */
- if (pg_fsync(dstfd) != 0)
- ereport(ERROR,
- (errcode_for_file_access(),
- errmsg("could not fsync file \"%s\": %m", 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.
+ */
+ pg_flush_data(dstfd, offset, nbytes);
+ }
if (close(dstfd))
ereport(ERROR,
@@ -187,3 +193,27 @@ copy_file(char *fromfile, char *tofile)
pfree(buffer);
}
+
+
+
+/*
+ * fsync a file
+ */
+static void
+fsync_fname(char *fname)
+{
+ int fd = BasicOpenFile(fname,
+ O_RDONLY | PG_BINARY,
+ S_IRUSR | S_IWUSR);
+
+ if (fd < 0)
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not open file \"%s\": %m", fname)));
+
+ if (pg_fsync(fd) != 0)
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not fsync file \"%s\": %m", fname)));
+ close(fd);
+}
--
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