Hi,
Since pg_test_fsync is supposed to simulate some aspects of
PostgreSQL's wal_sync_method settings, I think it should be updated to
use the same system calls (which changed in v12). That's mostly on
principle, though in practice, on one system I've managed to see a
small measurable difference.
I left the fsync-after-closing and non-sync'd tests using write(),
because they weren't using lseek(). The latter case is arguably a bit
odd because it's not overwriting pre-allocated blocks, unlike the
earlier tests.
From 0229b1341afaef812232f6f031ee7ffb5de76080 Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.mu...@gmail.com>
Date: Sat, 9 Jan 2021 23:37:18 +1300
Subject: [PATCH] Use pg_pwrite() in pg_test_fsync.
For consistency with the PostgreSQL behavior we're tring to simulate,
use pwrite() instead of lseek() + write().
---
src/bin/pg_test_fsync/pg_test_fsync.c | 43 +++++++++++++++------------
1 file changed, 24 insertions(+), 19 deletions(-)
diff --git a/src/bin/pg_test_fsync/pg_test_fsync.c b/src/bin/pg_test_fsync/pg_test_fsync.c
index 3eddd983c6..693a9478ad 100644
--- a/src/bin/pg_test_fsync/pg_test_fsync.c
+++ b/src/bin/pg_test_fsync/pg_test_fsync.c
@@ -290,10 +290,11 @@ test_sync(int writes_per_op)
for (ops = 0; alarm_triggered == false; ops++)
{
for (writes = 0; writes < writes_per_op; writes++)
- if (write(tmpfile, buf, XLOG_BLCKSZ) != XLOG_BLCKSZ)
+ if (pg_pwrite(tmpfile,
+ buf,
+ XLOG_BLCKSZ,
+ writes * XLOG_BLCKSZ) != XLOG_BLCKSZ)
die("write failed");
- if (lseek(tmpfile, 0, SEEK_SET) == -1)
- die("seek failed");
}
STOP_TIMER;
close(tmpfile);
@@ -315,11 +316,12 @@ test_sync(int writes_per_op)
for (ops = 0; alarm_triggered == false; ops++)
{
for (writes = 0; writes < writes_per_op; writes++)
- if (write(tmpfile, buf, XLOG_BLCKSZ) != XLOG_BLCKSZ)
+ if (pg_pwrite(tmpfile,
+ buf,
+ XLOG_BLCKSZ,
+ writes * XLOG_BLCKSZ) != XLOG_BLCKSZ)
die("write failed");
fdatasync(tmpfile);
- if (lseek(tmpfile, 0, SEEK_SET) == -1)
- die("seek failed");
}
STOP_TIMER;
close(tmpfile);
@@ -339,12 +341,13 @@ test_sync(int writes_per_op)
for (ops = 0; alarm_triggered == false; ops++)
{
for (writes = 0; writes < writes_per_op; writes++)
- if (write(tmpfile, buf, XLOG_BLCKSZ) != XLOG_BLCKSZ)
+ if (pg_pwrite(tmpfile,
+ buf,
+ XLOG_BLCKSZ,
+ writes * XLOG_BLCKSZ) != XLOG_BLCKSZ)
die("write failed");
if (fsync(tmpfile) != 0)
die("fsync failed");
- if (lseek(tmpfile, 0, SEEK_SET) == -1)
- die("seek failed");
}
STOP_TIMER;
close(tmpfile);
@@ -362,12 +365,13 @@ test_sync(int writes_per_op)
for (ops = 0; alarm_triggered == false; ops++)
{
for (writes = 0; writes < writes_per_op; writes++)
- if (write(tmpfile, buf, XLOG_BLCKSZ) != XLOG_BLCKSZ)
+ if (pg_pwrite(tmpfile,
+ buf,
+ XLOG_BLCKSZ,
+ writes * XLOG_BLCKSZ) != XLOG_BLCKSZ)
die("write failed");
if (pg_fsync_writethrough(tmpfile) != 0)
die("fsync failed");
- if (lseek(tmpfile, 0, SEEK_SET) == -1)
- die("seek failed");
}
STOP_TIMER;
close(tmpfile);
@@ -393,8 +397,10 @@ test_sync(int writes_per_op)
for (ops = 0; alarm_triggered == false; ops++)
{
for (writes = 0; writes < writes_per_op; writes++)
- if (write(tmpfile, buf, XLOG_BLCKSZ) != XLOG_BLCKSZ)
-
+ if (pg_pwrite(tmpfile,
+ buf,
+ XLOG_BLCKSZ,
+ writes * XLOG_BLCKSZ) != XLOG_BLCKSZ)
/*
* This can generate write failures if the filesystem has
* a large block size, e.g. 4k, and there is no support
@@ -402,8 +408,6 @@ test_sync(int writes_per_op)
* size, e.g. XFS.
*/
die("write failed");
- if (lseek(tmpfile, 0, SEEK_SET) == -1)
- die("seek failed");
}
STOP_TIMER;
close(tmpfile);
@@ -457,11 +461,12 @@ test_open_sync(const char *msg, int writes_size)
for (ops = 0; alarm_triggered == false; ops++)
{
for (writes = 0; writes < 16 / writes_size; writes++)
- if (write(tmpfile, buf, writes_size * 1024) !=
+ if (pg_pwrite(tmpfile,
+ buf,
+ writes_size * 1024,
+ writes * writes_size * 1024) !=
writes_size * 1024)
die("write failed");
- if (lseek(tmpfile, 0, SEEK_SET) == -1)
- die("seek failed");
}
STOP_TIMER;
close(tmpfile);
--
2.20.1
