Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Thu, 13 Feb 2020 12:36:09 +0100 | Subject | Re: [PATCH 00/28] PM: QoS: Get rid of unuseful code and rework CPU latency QoS interface |
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On Thu, Feb 13, 2020 at 11:50 AM Amit Kucheria <amit.kucheria@linaro.org> wrote: > > On Thu, Feb 13, 2020 at 3:47 PM Rafael J. Wysocki <rafael@kernel.org> wrote: > > > > On Thu, Feb 13, 2020 at 8:10 AM Amit Kucheria <amit.kucheria@linaro.org> wrote: > > > > > > On Wed, Feb 12, 2020 at 5:09 AM Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > > > > > > > > Hi All, > > > > > > > > This series of patches is based on the observation that after commit > > > > c3082a674f46 ("PM: QoS: Get rid of unused flags") the only global PM QoS class > > > > in use is PM_QOS_CPU_DMA_LATENCY, but there is still a significant amount of > > > > code dedicated to the handling of global PM QoS classes in general. That code > > > > takes up space and adds overhead in vain, so it is better to get rid of it. > > > > > > > > Moreover, with that unuseful code removed, the interface for adding QoS > > > > requests for CPU latency becomes inelegant and confusing, so it is better to > > > > clean it up. > > > > > > > > Patches [01/28-12/28] do the first part described above, which also includes > > > > some assorted cleanups of the core PM QoS code that doesn't go away. > > > > > > > > Patches [13/28-25/28] rework the CPU latency QoS interface (in the classic > > > > "define stubs, migrate users, change the API proper" manner), patches > > > > [26-27/28] update the general comments and documentation to match the code > > > > after the previous changes and the last one makes the CPU latency QoS depend > > > > on CPU_IDLE (because cpuidle is the only user of its target value today). > > > > > > > > The majority of the patches in this series don't change the functionality of > > > > the code at all (at least not intentionally). > > > > > > > > Please refer to the changelogs of individual patches for details. > > > > > > Hi Rafael, > > > > > > Nice cleanup to the code and docs. > > > > > > I've reviewed the series, and briefly tested it by setting latencies > > > from userspace. Can we not remove the debugfs interface? It is a quick > > > way to check the global cpu latency clamp on the system from userspace > > > without setting up tracepoints or writing a program to read > > > /dev/cpu_dma_latency. > > > > Come on. > > > > What about in Python? > > > > #!/usr/bin/env python > > import numpy as np > > > > if __name__ == '__main__': > > f = open("/dev/cpu_dma_latency", "r") > > print(np.fromfile(f, dtype=np.int32, count=1)) > > f.close() > > > > And probably you can do it in at least 20 different ways. :-) > > Indeed, I can, just not as straightforward as "cat /debugfs/filename" > when you don't have python or perl in your buildroot initramfs. > > Some hexdump/od acrobatics will yield the value, I guess.
Right,
# hexdump --format '"%d\n"' /dev/cpu_dma_latency
works just fine, actually.
Thanks!
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