On Wed, Sep 25, 2013 at 1:20 AM, Robert Haas <robertmh...@gmail.com> wrote:
> On Tue, Sep 24, 2013 at 5:04 AM, David Rowley <dgrowle...@gmail.com> > wrote: > >> So... I guess the question that I'd ask is, if you write a PL/pgsql > >> function that does RAISE NOTICE in a loop a large number of times, can > >> you measure any difference in how fast that function executes on the > >> patch and unpatched code? If so, how much? > > I do see a 15-18% slow down with the patched version, so perhaps I'll > need > > to look to see if I can speed it up a bit, although I do feel this > benchmark > > is not quite a normal workload. > > Ouch! That's pretty painful. I agree that's not a normal workload, > but I don't think it's an entirely unfair benchmark, either. There > certainly are people who suffer because of the cost of logging as > things are; for example, log_min_duration_statement is commonly used > and can produce massive amounts of output on a busy system. > > I wouldn't mind too much if the slowdown you are seeing only occurred > when the feature is actually used, but taking a 15-18% hit on logging > even when the new formatting features aren't being used seems too > expensive to me. > > Ok, I think I've managed to narrow the performance gap to just about nothing but noise, though to do this the code is now a bit bigger. I've added a series of tests to see if the padding is > 0 and if it's not then I'm doing things the old way. I've also added a some code which does a fast test to see if it is worth while calling the padding processing function. This is just a simple if (*p <= '9'), I'm not completely happy with that as it does look a bit weird, but to compensate I've added a good comment to explain what it is doing. Please find attached the new patch ... version v0.5 and also updated benchmark results. Regards David -- > Robert Haas > EnterpriseDB: http://www.enterprisedb.com > The Enterprise PostgreSQL Company >
log_line_prefix_benchmark_stresslog_v0.5.xls
Description: MS-Excel spreadsheet
log_line_formatting_v0.5.patch
Description: Binary data
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