| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Florian Weimer <fw(at)deneb(dot)enyo(dot)de> |
| Cc: | Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: gettimeofday is at the end of its usefulness? |
| Date: | 2016-12-29 21:02:31 |
| Message-ID: | 4130.1483045351@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Florian Weimer <fw(at)deneb(dot)enyo(dot)de> writes:
> * Tom Lane:
>> On Linux (RHEL6, 2.4GHz x86_64), I find that gettimeofday(),
>> clock_gettime(CLOCK_MONOTONIC), and clock_gettime(CLOCK_REALTIME)
>> all take about 40ns. Of course gettimeofday() only has 1us resolution,
>> but the other two have perhaps 10ns resolution (I get no duplicate
>> readings in a tight loop).
> Isn't this very specific to kernel and glibc versions, depending on
> things like CONFIG_HZ settings and what level of vDSO support has been
> backported?
No doubt, but I have yet to find a platform where clock_gettime() exists
but performs worse than gettimeofday(). Do you know of one?
regards, tom lane
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