Re: [bitbake-devel][PATCH V2] runqueue.py: fix PSI check logic

[Ola x Nilsson <ola.x.nilsson@axis.com>]

On Tue, May 23 2023, Randy MacLeod via lists.openembedded.org wrote:

> On 2023-05-22 22:09, Qi.Chen@windriver.com wrote:
>> From: Chen Qi<Qi.Chen@windriver.com>
>>
>> The current logic is not correct because if the time interval
>> between the current check and the last check is very small, the PSI
>> checker is not likely to block things even if the system is heavy
>> loaded.
>>
>> It's not good to calculate the value too often. So we change to a 1s
>> check. As a build will usually take at least minutes, using the 1s value
>> seems reasonable.
>
> I don't have time to check today but I'm not convinced that this is true.
>
> I suspect that in the typical case, it would be okay but there will be
> workloads (perhaps rare workloads) where you want to check more often.
>
> The 1 second intervals where we no longer launch new work may
> result in a significantly longer build. IIRC, our benchmark was building
> core-image-minimal on a 24 core system without PSI regulation and then
> with it set to 300. I'd look at the elapsed time and the
> buildchart/bootchart:
>    scripts/pybootchartgui/README.pybootchart
>
> Ola, have you been able to test this and if not, can you?
>

This patch is identical to the V1 except for the commit message, so I
consider it

Tested-By: Ola Nilsson <ola.x.nilsson@axis.com>

/Ola

> All for today.
>
> ../Randy
>
>
>>
>> Signed-off-by: Chen Qi<Qi.Chen@windriver.com>
>> ---
>>   bitbake/lib/bb/runqueue.py | 29 ++++++++++++++---------------
>>   1 file changed, 14 insertions(+), 15 deletions(-)
>>
>> diff --git a/bitbake/lib/bb/runqueue.py b/bitbake/lib/bb/runqueue.py
>> index 02f1474540..4d49d25153 100644
>> --- a/bitbake/lib/bb/runqueue.py
>> +++ b/bitbake/lib/bb/runqueue.py
>> @@ -179,6 +179,7 @@ class RunQueueScheduler(object):
>>                       self.prev_memory_pressure = memory_pressure_fds.readline().split()[4].split("=")[1]
>>                       self.prev_pressure_time = time.time()
>>                   self.check_pressure = True
>> +                self.psi_exceeded = False
>>               except:
>> bb.note("The /proc/pressure files can't be read. Continuing build
> without monitoring pressure")
>>                   self.check_pressure = False
>> @@ -191,6 +192,10 @@ class RunQueueScheduler(object):
>>           BB_PRESSURE_MAX_{CPU|IO|MEMORY} are set, return True if above threshold.
>>           """
>>           if self.check_pressure:
>> +            now = time.time()
>> +            tdiff = now - self.prev_pressure_time
>> +            if tdiff < 1.0:
>> +                return self.psi_exceeded
>>               with open("/proc/pressure/cpu") as cpu_pressure_fds, \
>>                   open("/proc/pressure/io") as io_pressure_fds, \
>>                   open("/proc/pressure/memory") as memory_pressure_fds:
>> @@ -198,21 +203,15 @@ class RunQueueScheduler(object):
>>                   curr_cpu_pressure = cpu_pressure_fds.readline().split()[4].split("=")[1]
>>                   curr_io_pressure = io_pressure_fds.readline().split()[4].split("=")[1]
>>                   curr_memory_pressure = memory_pressure_fds.readline().split()[4].split("=")[1]
>> -                now = time.time()
>> -                tdiff = now - self.prev_pressure_time
>> -                if tdiff > 1.0:
>> - exceeds_cpu_pressure = self.rq.max_cpu_pressure and
> (float(curr_cpu_pressure) - float(self.prev_cpu_pressure)) / tdiff >
> self.rq.max_cpu_pressure
>> - exceeds_io_pressure = self.rq.max_io_pressure and
> (float(curr_io_pressure) - float(self.prev_io_pressure)) / tdiff >
> self.rq.max_io_pressure
>> - exceeds_memory_pressure = self.rq.max_memory_pressure and
> (float(curr_memory_pressure) - float(self.prev_memory_pressure)) /
> tdiff > self.rq.max_memory_pressure
>> -                    self.prev_cpu_pressure = curr_cpu_pressure
>> -                    self.prev_io_pressure = curr_io_pressure
>> -                    self.prev_memory_pressure = curr_memory_pressure
>> -                    self.prev_pressure_time = now
>> -                else:
>> - exceeds_cpu_pressure = self.rq.max_cpu_pressure and
> (float(curr_cpu_pressure) - float(self.prev_cpu_pressure)) >
> self.rq.max_cpu_pressure
>> - exceeds_io_pressure = self.rq.max_io_pressure and
> (float(curr_io_pressure) - float(self.prev_io_pressure)) >
> self.rq.max_io_pressure
>> - exceeds_memory_pressure = self.rq.max_memory_pressure and
> (float(curr_memory_pressure) - float(self.prev_memory_pressure)) >
> self.rq.max_memory_pressure
>> -            return (exceeds_cpu_pressure or exceeds_io_pressure or exceeds_memory_pressure)
>> + exceeds_cpu_pressure = self.rq.max_cpu_pressure and
> (float(curr_cpu_pressure) - float(self.prev_cpu_pressure)) / tdiff >
> self.rq.max_cpu_pressure
>> + exceeds_io_pressure = self.rq.max_io_pressure and
> (float(curr_io_pressure) - float(self.prev_io_pressure)) / tdiff >
> self.rq.max_io_pressure
>> + exceeds_memory_pressure = self.rq.max_memory_pressure and
> (float(curr_memory_pressure) - float(self.prev_memory_pressure)) /
> tdiff > self.rq.max_memory_pressure
>> +                self.prev_cpu_pressure = curr_cpu_pressure
>> +                self.prev_io_pressure = curr_io_pressure
>> +                self.prev_memory_pressure = curr_memory_pressure
>> +                self.prev_pressure_time = now
>> +                self.psi_exceeded = exceeds_cpu_pressure or exceeds_io_pressure or exceeds_memory_pressure
>> +            return self.psi_exceeded
>>           return False
>>         def next_buildable_task(self):


-- 
Ola x Nilsson