On Sat, Mar 12, 2016 at 08:33:55PM +0300, Vladimir Borodin wrote:
> That’s why proposal included GUC for that with a default to turn timings
> measuring off. I don’t remember any objections against that.
>
> And I’m absolutely sure that a real highload production (which of course
> doesn’t use virtualization and windows) can’t exist without measuring timings.
> Oracle guys have written several chapters (!) about that [0]. Long story short,
> sampling doesn’t give enough precision. I have shown overhead [1] on bare metal
> linux with high stressed lwlocks worload. BTW Oracle doesn’t give you any ways
> to turn timings measurement off, even with hidden parameters. All other
> commercial databases have waits monitoring with timings measurement. Let’s do
> it and turn it off by default so that all other platforms don’t suffer from it.
I realize that users of other databases have found sampling to be
insufficient, but I think we need to use the Postgres sampling method in
production to see if it is insufficient for Postgres as well. We can't
design based on the limitations of other databases.
Also, we have enabled the sampling method in 9.6 that we know can be
enabled on every platform with limited overhead. We can add additional
potential-overhead methods in later releases.
Frankly, it would be odd to add these features in the opposite order,
and the stubbornness of some in this thread to understand that is
concerning.
-- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB
http://enterprisedb.com
+ As you are, so once was I. As I am, so you will be. +
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