RE: LIO/sec per CPU limit? Is it Hardware or Oracle code?

From: Reen, Elizabeth <"Reen,>
Date: Thu, 10 Aug 2017 15:13:01 +0000
Message-ID: <>

Are the disks set up identically?


From: [] On Behalf Of Henry Poras Sent: Wednesday, August 09, 2017 5:46 PM To: ORACLE-L
Subject: LIO/sec per CPU limit? Is it Hardware or Oracle code?

I have two identical servers (or so I am told), but application work is running 2-3 times slower on one than the other. Using Tanel's snapper, I see that all active sessions are all on CPU. Viewing top shows me the same thing, each session pegs a cpu. We also found that it wasn't particular SQL that slowed down across severs, but it looked like everything was slow. A select count(*) from dba_objects showed this behavior as did Jonathan Lewis's kill_cpu script. This gave me something to test with. Running a 10046, I saw the same amount of resource utilization (parse count, fetch count, cr count, ...), no contention (wait events), but one server finished 2.5 times faster than the other. Looking at session stats through snapper, I see that the number of session logical reads per sec (~all of which are consistent reads) is ~ 2.5 times higher on one server than the other. That explains why it takes one longer to finish.

So, now what?? Why is one server giving me 350k consistent gets/per second and the other is ~800k? Is it hardware? /proc/cpuinfo shows the same cpu for each box. Is it hidden in the Oracle code path? I realize that not all LIO are created equal, but how do I check this? I am running on SE12.1.0.1

Any and all thoughts welcome.


Received on Thu Aug 10 2017 - 17:13:01 CEST

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