On 12/01/2014 09:51 PM, Marco Nenciarini wrote:
> I think this is a leftover, as you don't use elog afterwards.
Good catch, fixed.
--
Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
>From 63edf0571961f2f2c7fd6a08b99e747ee39a3377 Mon Sep 17 00:00:00 2001
From: Craig Ringer <cr...@2ndquadrant.com>
Date: Fri, 12 Sep 2014 12:41:35 +0800
Subject: [PATCH 1/2] Use GetSystemTimeAsFileTime directly in windows
gettimeofday
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PostgreSQL was calling GetSystemTime followed by SystemTimeToFileTime in the
win32 port gettimeofday function. This is not necessary and limits the reported
precision to the 1ms granularity that the SYSTEMTIME struct can represent. By
using GetSystemTimeAsFileTime we avoid unnecessary conversions and capture
timestamps at 100ns granularity, which is then rounded to 1µs granularity for
storage in a PostgreSQL timestamp.
On most Windows systems this change will actually have no significant effect as
the system timer tick is typically between 1ms and 15ms depending on what timer
resolution currently running applications have requested. You can check this
with clockres.exe from sysinternals. Despite the platform limiation this change
still permits capture of finer timestamps where the system is capable of
producing them and it gets rid of an unnecessary syscall.
Future work may permit use of GetSystemTimePreciseAsFileTime on Windows 8 and
Windows Server 2012 for higher resolution time capture. This call has the same
interface as GetSystemTimeAsFileTime.
---
src/port/gettimeofday.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/src/port/gettimeofday.c b/src/port/gettimeofday.c
index 75a9199..73ec406 100644
--- a/src/port/gettimeofday.c
+++ b/src/port/gettimeofday.c
@@ -44,16 +44,14 @@ int
gettimeofday(struct timeval * tp, struct timezone * tzp)
{
FILETIME file_time;
- SYSTEMTIME system_time;
ULARGE_INTEGER ularge;
- GetSystemTime(&system_time);
- SystemTimeToFileTime(&system_time, &file_time);
+ GetSystemTimeAsFileTime(&file_time);
ularge.LowPart = file_time.dwLowDateTime;
ularge.HighPart = file_time.dwHighDateTime;
tp->tv_sec = (long) ((ularge.QuadPart - epoch) / 10000000L);
- tp->tv_usec = (long) (system_time.wMilliseconds * 1000);
+ tp->tv_usec = (long) (((ularge.QuadPart - epoch) % 10000000L) / 10);
return 0;
}
--
1.9.3
>From 035bb3b19f93560d18834d2daf397c70e1555015 Mon Sep 17 00:00:00 2001
From: Craig Ringer <cr...@2ndquadrant.com>
Date: Thu, 18 Sep 2014 23:02:14 +0800
Subject: [PATCH 2/2] Use GetSystemTimePreciseAsFileTime when available
This will cause PostgreSQL on Windows 8 or Windows Server 2012 to
obtain high-resolution timestamps while allowing the same binaries
to run without problems on older releases.
---
src/backend/main/main.c | 6 ++++++
src/include/port.h | 2 ++
src/port/gettimeofday.c | 52 +++++++++++++++++++++++++++++++++++++++++++++++--
3 files changed, 58 insertions(+), 2 deletions(-)
diff --git a/src/backend/main/main.c b/src/backend/main/main.c
index c51b391..73c30c5 100644
--- a/src/backend/main/main.c
+++ b/src/backend/main/main.c
@@ -260,6 +260,12 @@ startup_hacks(const char *progname)
/* In case of general protection fault, don't show GUI popup box */
SetErrorMode(SEM_FAILCRITICALERRORS | SEM_NOGPFAULTERRORBOX);
+
+#ifndef HAVE_GETTIMEOFDAY
+ /* Figure out which syscall to use to capture timestamp information */
+ init_win32_gettimeofday();
+#endif
+
}
#endif /* WIN32 */
diff --git a/src/include/port.h b/src/include/port.h
index 94a0e2f..58677ec 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -328,6 +328,8 @@ extern FILE *pgwin32_popen(const char *command, const char *type);
#ifndef HAVE_GETTIMEOFDAY
/* Last parameter not used */
extern int gettimeofday(struct timeval * tp, struct timezone * tzp);
+/* On windows we need to call some backend start setup for accurate timing */
+extern void init_win32_gettimeofday(void);
#endif
#else /* !WIN32 */
diff --git a/src/port/gettimeofday.c b/src/port/gettimeofday.c
index 73ec406..ab4f491 100644
--- a/src/port/gettimeofday.c
+++ b/src/port/gettimeofday.c
@@ -35,9 +35,57 @@
static const unsigned __int64 epoch = UINT64CONST(116444736000000000);
/*
+ * Both GetSystemTimeAsFileTime and GetSystemTimePreciseAsFileTime share a
+ * signature, so we can just store a pointer to whichever we find. This
+ * is the pointer's type.
+ */
+typedef VOID (WINAPI *PgGetSystemTimeFn)(LPFILETIME);
+/* Storage for the function we pick at runtime */
+static PgGetSystemTimeFn pg_get_system_time = NULL;
+
+/*
+ * During backend startup, determine if GetSystemTimePreciseAsFileTime is
+ * available and use it; if not, fall back to GetSystemTimeAsFileTime.
+ */
+void
+init_win32_gettimeofday(void)
+{
+ /*
+ * Because it's guaranteed that kernel32.dll will be linked into our
+ * address space already, we don't need to LoadLibrary it and worry about
+ * closing it afterwards, so we're not using Pg's dlopen/dlsym() wrapper.
+ *
+ * We'll just look up the address of GetSystemTimePreciseAsFileTime if
+ * present.
+ *
+ * While we could look up the Windows version and skip this on Windows
+ * versions below Windows 8 / Windows Server 2012 there isn't much point,
+ * and determining the windows version is its self somewhat Windows version
+ * and development SDK specific...
+ */
+ pg_get_system_time = (PgGetSystemTimeFn) GetProcAddress(
+ GetModuleHandle(TEXT("kernel32.dll")),
+ "GetSystemTimePreciseAsFileTime");
+ if (pg_get_system_time == NULL)
+ {
+ /*
+ * The expected error from GetLastError() is ERROR_PROC_NOT_FOUND, if
+ * the function isn't present. No other error should occur.
+ *
+ * It's too early in startup to elog(...) if we get some unexpected
+ * error, and not serious enough to warrant a fprintf to stderr about
+ * it or save the error and report it later. So silently fall back to
+ * GetSystemTimeAsFileTime irrespective of why the failure occurred.
+ */
+ pg_get_system_time = &GetSystemTimeAsFileTime;
+ }
+
+}
+
+/*
* timezone information is stored outside the kernel so tzp isn't used anymore.
*
- * Note: this function is not for Win32 high precision timing purpose. See
+ * Note: this function is not for Win32 high precision timing purposes. See
* elapsed_time().
*/
int
@@ -46,7 +94,7 @@ gettimeofday(struct timeval * tp, struct timezone * tzp)
FILETIME file_time;
ULARGE_INTEGER ularge;
- GetSystemTimeAsFileTime(&file_time);
+ (*pg_get_system_time)(&file_time);
ularge.LowPart = file_time.dwLowDateTime;
ularge.HighPart = file_time.dwHighDateTime;
--
1.9.3
--
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