Hi Leonardo,
On 6/11/19 12:17 AM, Leonardo Bras wrote:
On Mon, 2019-06-10 at 12:02 +0530, Anju T Sudhakar wrote:
Nest and core imc(In-memory Collection counters) assigns a particular
cpu as the designated target for counter data collection.
During system boot, the first online cpu in a chip gets assigned as
the designated cpu for that chip(for nest-imc) and the first online cpu
in a core gets assigned as the designated cpu for that core(for core-imc).
If the designated cpu goes offline, the next online cpu from the same
chip(for nest-imc)/core(for core-imc) is assigned as the next target,
and the event context is migrated to the target cpu.
Currently, cpumask_any_but() function is used to find the target cpu.
Though this function is expected to return a `random` cpu, this always
returns the next online cpu.
If all cpus in a chip/core is offlined in a sequential manner, starting
from the first cpu, the event migration has to happen for all the cpus
which goes offline. Since the migration process involves a grace period,
the total time taken to offline all the cpus will be significantly high.
Seems like a very interesting work.
Out of curiosity, have you used 'chcpu -d' to create your benchmark?
Here I did not use chcpu to disable the cpu.
I used a script which will offline cpus 88-175 by echoing `0` to
/sys/devices/system/cpu/cpu*/online.
Regards,
Anju
