USEOSTIME Performance Degradation ?

Posted in 2014

Summary

Mark Jalkiewicz asked whether enabling USEOSTIME for sub-second CURRENT costs performance on Informix 11.70.FC7 on AIX 6.1. Art Kagel said developers told him no; the default is off because gettimeofday() was slow on old Xenix and is fast on modern systems. Benjamin Thompson noted the 11.70.FC8 default onconfig comment still says subsecond precision can degrade performance.

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Topics: Performance & Tuning

MARK JALKIEWICZ — Wed, 30 Jul 2014 21:18:37 — source: IIUG Forums & Mailing Lists

The need has arisen for sub second granularity with CURRENT. Question is does turning this on result in any noticeable performance degradation and if so is it more system wide or specific to just the application ? AIX 6.1. Informix 11.70.FC7 Thanks, Mark

↪ replying to MARK JALKIEWICZ

Art Kagel — Wed, 30 Jul 2014 21:56:34 — source: IIUG Forums & Mailing Lists

I was told by Informix developers that the answer is "no". The default is off (0) because back in the old days SCO Xenix was the most popular platform for Informix and the gettimeofday() system call was very slow on Xenix. ASAIK in all modern UNIX and Linux implementations gettimeofday() is very fast. Fast enough that the test program I wrote to determine the subsecond resolution of gettimeofday() for an applications I was writing would get the same result for more than one consecutive call on most platforms. On the platforms with the finest resolution (about 0.3ms) I'd get the same result zero to 3 time in a row in a tight loop that just called gettimeofday(), subtracted the previous value, printed the result, and copied the data to the 'prev' copy. That was about 10 years ago when systems were slower. Why the default has never been changed I will never understand. Art Art S. Kagel, Principal Consultant ASK Database Management Blog: http://informix-myview.blogspot.com/ Disclaimer: Please keep in mind that my own opinions are my own opinions and do not reflect on the IIUG, nor any other organization with which I am associated either explicitly, implicitly, or by inference. Neither do those opinions reflect those of other individuals affiliated with any entity with which I am affiliated nor those of the entities themselves. On Wed, Jul 30, 2014 at 5:18 PM, MARK JALKIEWICZ < mark.jalkiewicz@verizon.net> wrote: > The need has arisen for sub second granularity with CURRENT. Question is > does > turning this on result in any noticeable performance degradation and if so > is > it more system wide or specific to just the application ? > > AIX 6.1. Informix 11.70.FC7 > > Thanks, > > Mark > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --001a11c1062879ebbb04ff703a93

↪ replying to Art Kagel

MARK JALKIEWICZ — Thu, 31 Jul 2014 13:30:00 — source: IIUG Forums & Mailing Lists

Thanks Art ! Mark

↪ replying to Art Kagel

BENJAMIN THOMPSON — Mon, 04 Aug 2014 14:03:46 — source: IIUG Forums & Mailing Lists

I wonder if the description in the default onconfig could be changed then. It was changed not so long ago but currently reads (11.70.FC8): # USEOSTIME - The precision of SQL statement timing. # Accepted values are 0 (precision to seconds) # and 1 (precision to subseconds). Subsecond # precision can degrade performance. :)