Re: gettimeofday is at the end of its usefulness?

От

Benedikt Grundmann

Тема

Дата

15 мая 2014 г. в 07:19:27

Msg-id

CADbMkNPEgbP_GThAvUdFu048zUpVGBHOeODUfGPKiEM-a4GXMw@mail.gmail.com

обсуждение

Ответ на

Re: gettimeofday is at the end of its usefulness? (Robert Haas)

Список

pgsql-hackers

Дерево обсуждения

gettimeofday is at the end of its usefulness? Tom Lane <tgl@sss.pgh.pa.us> 13 мая 2014 г. в 22:58:15

Re: gettimeofday is at the end of its usefulness? Andres Freund <andres@2ndquadrant.com> 15 мая 2014 г. в 11:21:18

Re: gettimeofday is at the end of its usefulness? Bruce Momjian <bruce@momjian.us> 15 мая 2014 г. в 18:56:18

Re: gettimeofday is at the end of its usefulness? Thom Brown <thom@linux.com> 8 июня 2016 г. в 11:41:35

Re: gettimeofday is at the end of its usefulness? Tom Lane <tgl@sss.pgh.pa.us> 8 июня 2016 г. в 14:56:40

Re: gettimeofday is at the end of its usefulness? Jim Nasby <Jim.Nasby@BlueTreble.com> 14 июня 2016 г. в 20:30:40

Re: gettimeofday is at the end of its usefulness? Robert Haas <robertmhaas@gmail.com> 7 июля 2016 г. в 18:43:37

Re: gettimeofday is at the end of its usefulness? Andres Freund <andres@anarazel.de> 7 июля 2016 г. в 18:48:38

Re: gettimeofday is at the end of its usefulness? Haribabu Kommi <kommi.haribabu@gmail.com> 25 августа 2016 г. в 05:12:44

Re: gettimeofday is at the end of its usefulness? Haribabu Kommi <kommi.haribabu@gmail.com> 14 сентября 2016 г. в 00:53:34

Re: [HACKERS] gettimeofday is at the end of its usefulness? Tom Lane <tgl@sss.pgh.pa.us> 27 декабря 2016 г. в 00:34:15

Re: [HACKERS] gettimeofday is at the end of its usefulness? Florian Weimer <fw@deneb.enyo.de> 29 декабря 2016 г. в 23:02:49

Re: [HACKERS] gettimeofday is at the end of its usefulness? Tom Lane <tgl@sss.pgh.pa.us> 30 декабря 2016 г. в 00:02:31

Re: [HACKERS] gettimeofday is at the end of its usefulness? Florian Weimer <fw@deneb.enyo.de> 13 января 2017 г. в 23:48:51

Re: [HACKERS] gettimeofday is at the end of its usefulness? Tom Lane <tgl@sss.pgh.pa.us> 13 января 2017 г. в 23:54:24

Re: [HACKERS] gettimeofday is at the end of its usefulness? Thomas Munro <thomas.munro@enterprisedb.com> 30 декабря 2016 г. в 00:05:39

Re: [HACKERS] gettimeofday is at the end of its usefulness? Tom Lane <tgl@sss.pgh.pa.us> 30 декабря 2016 г. в 00:18:42

Re: [HACKERS] gettimeofday is at the end of its usefulness? Greg Stark <stark@mit.edu> 27 декабря 2016 г. в 04:35:05

Re: [HACKERS] gettimeofday is at the end of its usefulness? Andres Freund <andres@anarazel.de> 27 декабря 2016 г. в 12:17:37

Re: [HACKERS] gettimeofday is at the end of its usefulness? Tom Lane <tgl@sss.pgh.pa.us> 27 декабря 2016 г. в 18:50:27

Re: [HACKERS] gettimeofday is at the end of its usefulness? Tom Lane <tgl@sss.pgh.pa.us> 30 декабря 2016 г. в 05:02:39

Re: [HACKERS] gettimeofday is at the end of its usefulness? Haribabu Kommi <kommi.haribabu@gmail.com> 4 января 2017 г. в 07:00:32

Re: gettimeofday is at the end of its usefulness? Greg Stark <stark@mit.edu> 14 мая 2014 г. в 03:34:56

Re: gettimeofday is at the end of its usefulness? Tom Lane <tgl@sss.pgh.pa.us> 14 мая 2014 г. в 03:42:55

Re: gettimeofday is at the end of its usefulness? Ants Aasma <ants@cybertec.at> 14 мая 2014 г. в 09:48:56

Re: gettimeofday is at the end of its usefulness? Robert Haas <robertmhaas@gmail.com> 14 мая 2014 г. в 11:41:36

Re: gettimeofday is at the end of its usefulness? Benedikt Grundmann <bgrundmann@janestreet.com> 15 мая 2014 г. в 07:19:27

Re: gettimeofday is at the end of its usefulness? Benedikt Grundmann <bgrundmann@janestreet.com> 15 мая 2014 г. в 07:20:34

Re: gettimeofday is at the end of its usefulness? Greg Stark <stark@mit.edu> 15 мая 2014 г. в 10:32:10

Re: gettimeofday is at the end of its usefulness? Benedikt Grundmann <bgrundmann@janestreet.com> 15 мая 2014 г. в 11:04:32

Re: gettimeofday is at the end of its usefulness? Andres Freund <andres@2ndquadrant.com> 15 мая 2014 г. в 11:15:14

Re: gettimeofday is at the end of its usefulness? Peter Geoghegan <pg@heroku.com> 13 мая 2014 г. в 23:33:37

Re: gettimeofday is at the end of its usefulness? Tom Lane <tgl@sss.pgh.pa.us> 14 мая 2014 г. в 00:16:36

Re: gettimeofday is at the end of its usefulness? Jeff Janes <jeff.janes@gmail.com> 14 мая 2014 г. в 04:58:12

I posted this on this mailing list before at Jane Street we have developed very fast code to get timing information based on TSC if available. It's all ocaml but well documented and mostly just calls to c functions so should be easy to port to C and we release it under a very liberal license so it should be no problem to take the ideas:

https://github.com/janestreet/core/blob/master/lib/time_stamp_counter.mli

Hope this is useful.

Bene

On Wed, May 14, 2014 at 12:41 PM, Robert Haas <robertmhaas@gmail.com> wrote:

On Tue, May 13, 2014 at 11:34 PM, Greg Stark <stark@mit.edu> wrote:
> I always assumed the kernel used rdtsc to implement some of the high
> performance timers. It can save the current time in a mapped page when
> it schedules a process and then in the vdso syscall (ie in user-space)
> it can use rdtsc to calculate the offset needed to adjust that
> timestamp to the current time. This seems consistent with your
> calculations that showed the 40ns overhead with +/- 10ns precision.

Crazy idea: Instead of trying to time precisely the amount of time we
spend in each node, configure a very-high frequency timer interrupt
(or background thread?) that does:

SomeGlobalVariablePointingToTheCurrentNode->profiling_counter++;

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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