Some more hugepages questions/thoughts
- From: <Christopher.Taylor2@xxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 1 May 2013 12:45:33 -0500
I'm just now beginning to work through the hugepages configuration on Linux 5.8
64-bit, running Oracle 10.2.0.4.
Dev and QA are both 3 node RAC systems running 4 separate databases in each
environment. (So node1 of each environment has 4 instances)
Prod has 1 database across 3 nodes (1 instance on each node)
If I wanted to follow the 80-20 rule (80% of memory for SGA, 20% for PGA/System
Processes), could I just configure huge page pool (vm.nr_hugepages) derived
from the 80% number? (As opposed to running the shell script provided by
metalink to give me an accurate number for vm.nr_hugepages).
The reason I ask this question is that the number of sessions/processes
connected varies widely during day/night cycles and the workload is much
different.
I'm trying to keep this simple (and perhaps I'm already overthinking it) but it
seems if I allocated roughly 80% of total memory to hugepages then I could fit
all my databases inside that pool as needed and practically never worry about
the system memory being overallocated (as long as I size my Oracle pools
correctly for each instance).
I was also under the impression that you could set the pagesize 2MB, 4MB etc on
Linux like you can on AIX - wouldn't that affect the vm.nr_hugepages figure
that is used?
So, if I wanted to do this, how could I back my way into the vm.nr_hugepages
starting from 128GB system memory:
128GB * 0.80 = 102.4 GB
ASM uses roughly 500MB - so now I have 101.9 GB.
So to be safe, let's use 101 GB as the available system memory I want to
allocate to hugepages.
How do I back into the nr_hugepages from here?
Regards,
Chris Taylor
Oracle DBA
Parallon IT&S
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