On Fri, 2019-07-05 at 11:48 -0700, Gordon Messmer wrote: > On 7/4/19 10:18 PM, Steven Tardy wrote: > > I would also look at power settings in the BIOS and c-state settings in the > > BIOS and OS as disabling c-states (often enabled by default to meet > > green/energy star compliance) can make a noticeable performance difference. > > I'd be surprised if it did, but now that you mention it, I think that we > should probably mention more often that CentOS's default performance > policy is power-saving, which will cut maximum performance in half. > Every physical system running CentOS should have run "tuned-adm profile > throughput-performance". > I'm a bit confused. I've just done some quick experiments on an HPC system. It was previously set to whatever the default is and then changed to "throughput-performance". There was no discernible change in computation time for on 8-core job (on a dual 4-core Xeon; don't judge, it's an old system I use for testing) - the overall time for the run was just under an hour for both give or take 10 seconds. So my question is, would the tuning parameters be expected to make a difference on long-term CPU bound processes? Or does the CPU just go at full speed if necessary? Does it depend on the CPU generation? I'm perfectly willing to set all my HPC cluster nodes to whatever is necessary to get the best performance, but will changing the profile to a performance one mean that the machine will use more power when idle? Finally, is there a decent online source where I can read up on what the different tuned profile/parameters mean. Thanks P.