On Tue, 26 Jun 2007 17:26:29 +0200 Ingo Molnar <[EMAIL PROTECTED]> wrote:
> > * Andrew Morton <[EMAIL PROTECTED]> wrote: > > > > > the patch improves the sysbench OLTP macrobenchmark significantly: > > > > > > Has that any real practical relevance? > > > > Interesting question. [...] > > i'm missing the <sarcastic> tag i guess ;-) > > <sarcastic> Oh my, does database macro-performance have any relevance to > Linux bread and butter markets in general. Boggle, it is a really > difficult question i suspect. </sarcastic> > > If we ignore those few million database and web server Linux boxes on > the market and concentrate purely on the few m68k boxes that are still > in existance, _then_ we might be doubtful about this question ;-) On my machine, time(2) doesn't do any syscall at all - it uses the vsyscall page. I'd be surprised if a database uses sys_time() either. > > [...] The patch adds a new test-n-branch to gettimeofday() so if > > gettimeofday() is used much more frequently than time(), we lose. > > given that the cost to sys_gettimeofday() is less than a cycle (we test > a value already in a register, with an unlikely hint), and the benefit > to sys_time() is around 6000 cycles (or more), sys_gettimeofday() would > have to be used thousands of times more frequently than sys_time() - > which it clearly isnt. As a test i just triggered a really X-intense > workload and for that gettimeofday-dominated landscape there was still 1 > sys_time() call for every 50 gettimeofday calls - so it's a small win > even for this X workload. So something in X is somehow calling sys_time()? How come, and is that an outlier? How generalisable is this observation? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
