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Re: review: pgbench - aggregation of info written into log

From: Andrew Dunstan <andrew(at)dunslane(dot)net>
To: Tatsuo Ishii <ishii(at)postgresql(dot)org>
Cc: tv(at)fuzzy(dot)cz, pgsql-hackers(at)postgresql(dot)org
Subject: Re: review: pgbench - aggregation of info written into log
Date: 2013-01-17 00:48:46
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
On 01/16/2013 06:48 PM, Tatsuo Ishii wrote:
>>> I'm looking into this as a committer.  It seems that this is the
>>> newest patch and the reviewer(Pavel) stated that it is ready for
>>> commit. However, I noticed that this patch adds a Linux/UNIX only
>>> feature(not available on Windows). So I would like to ask cores if
>>> this is ok or not.
>> I haven't been following the thread, but if the complaint is that
>> Windows doesn't have accurate high-resolution timers, which is what it
>> kinda looks like from the rest of your message, then it's not
>> true. Every version since Windows2000 has had
>> QueryPerformanceCounter()/QueryPerformanceFrequency(). And we use it:
>> see src/include/portability/instr_time.h
> In my understanding the problem is not related to resolution.
>> If that's not the problem, then can someone please point me at the
>> message that sets the problem out clearly, or else just recap it?
> It seems instr_time.h on Windows simply does not provide current
> timestamp. From pgbench.c:
> 		/*
> 		 * if transaction finished, record the time it took in the log
> 		 */
> 		if (logfile && commands[st->state + 1] == NULL)
> 		{
> 			instr_time	now;
> 			instr_time	diff;
> 			double		usec;
> 			diff = now;
> 			INSTR_TIME_SUBTRACT(diff, st->txn_begin);
> 			usec = (double) INSTR_TIME_GET_MICROSEC(diff);
> #ifndef WIN32
> 			/* This is more than we really ought to know about instr_time */
> 			fprintf(logfile, "%d %d %.0f %d %ld %ld\n",
> 					st->id, st->cnt, usec, st->use_file,
> 					(long) now.tv_sec, (long) now.tv_usec);
> #else
> 			/* On Windows, instr_time doesn't provide a timestamp anyway */
> 			fprintf(logfile, "%d %d %.0f %d 0 0\n",
> 					st->id, st->cnt, usec, st->use_file);
> #endif
> 		}

This might be way more than we want to do, but there is an article that 
describes some techniques for doing what seems to be missing (AIUI):




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