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Re: LWLock contention: I think I understand the problem

From: Tatsuo Ishii <t-ishii(at)sra(dot)co(dot)jp>
To: pgman(at)candle(dot)pha(dot)pa(dot)us
Cc: tgl(at)sss(dot)pgh(dot)pa(dot)us, pgsql-hackers(at)postgresql(dot)org, jwbaker(at)acm(dot)org
Subject: Re: LWLock contention: I think I understand the problem
Date: 2002-01-03 09:00:10
Message-ID: 20020103180010S.t-ishii@sra.co.jp (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-odbc
> I guess what really bothers me now is why the select() in 7.1 wasn't
> slower than it was.  We made 7.2 especially for multicpu systems, and
> here we have identical performance to 7.1.  Tatsuo, is AIX capable of
> <10 millisecond sleeps?  I see there is such a program in the archives
> from Tom Lane:
> 
> 	http://fts.postgresql.org/db/mw/msg.html?mid=1217731
> 
> Tatsuo, can you run that program on the AIX box and tell us what it
> reports?  It would not surprise me if AIX supported sub-10ms select()
> timing because I have heard AIX is a mixing of Unix and IBM mainframe
> code.
> 
> I have attached a clean version of the code because the web mail archive
> munged the C code.  I called it tst1.c.  If you compile it and run it
> like this:
> 
> 	#$ time tst1 1
> 
> 	real    0m10.013s
> 	user    0m0.000s
> 	sys     0m0.004s
> 
> This runs select(1) 1000 times, meaning 10ms per select for BSD/OS.

Bingo. It seems AIX 5L can run select() at 1ms timing.

bash-2.04$ time ./a.out 1

real    0m1.027s
user    0m0.000s
sys     0m0.000s
--
Tatsuo Ishii

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