Messages in this thread |  | | Subject | Re: [PATCH] genirq: only scan the present CPUs | From | Dou Liyang <> | Date | Fri, 6 Apr 2018 16:42:14 +0800 |
| |
Hi Thomas, Peter,
At 04/03/2018 07:23 PM, Peter Zijlstra wrote: > On Tue, Apr 03, 2018 at 12:25:56PM +0200, Thomas Gleixner wrote: >> On Mon, 2 Apr 2018, Li RongQing wrote: >> >>> lots of application will read /proc/stat, like ps and vmstat, but we >>> find the reading time are spreading on Purley platform which has lots >>> of possible CPUs and interrupt. >>> >>> To reduce the reading time, only scan the present CPUs, not all possible >>> CPUs, which speeds the reading of /proc/stat 20 times on Purley platform >>> which has 56 present CPUs, and 224 possible CPUs >> >> Why is BIOS/ACPI telling the kernel that there are 224 possible CPUs unless >> it supports physical CPU hotplug. > > BIOS is crap, news at 11. I've got boxes like that too. Use > possible_cpu=$nr if you're bothered by it -- it's what I do. >
Yes, I think so. it is a manual way to reset the number.
For this situation, I am investigating to restrict the number of possible CPUs automatically, But, due to the limitation of ACPI subsystem, I can do it _before_ setup_percpu_area where the number will be used.
But, I can provider an indicator to tell the system that whether the physical CPU hotplug is support or not later. Can we use this indicator like that in this situation:
if ture
Using for_each_possible_cpu(cpu) else
Using for_each_present_cpu(cpu)
Thanks,
dou
> >
|  |