From: Tri Vo <email@example.com> To: "Rafael J. Wysocki" <firstname.lastname@example.org> Cc: Sandeep Patil <email@example.com>, Viresh Kumar <firstname.lastname@example.org>, Hridya Valsaraju <email@example.com>, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, LKML <email@example.com> Subject: Re: Alternatives to /sys/kernel/debug/wakeup_sources Date: Tue, 18 Jun 2019 16:15:14 -0700 Message-ID: <CANA+-vCMK6u1n9gXf2+v5dFn_tGfr1PT8d7W4d2BCzw+B-HvYw@mail.gmail.com> (raw) In-Reply-To: <4587569.x9DSL43cXO@kreacher> On Tue, Jun 18, 2019 at 2:23 PM Rafael J. Wysocki <firstname.lastname@example.org> wrote: > > On Tuesday, June 18, 2019 10:17:16 PM CEST Sandeep Patil wrote: > > > > Hi Rafael, Viresh etc. > > > > On Tue, Jun 11, 2019 at 10:31:16AM -0700, Tri Vo wrote: > > > On Tue, Jun 4, 2019 at 5:23 PM Tri Vo <email@example.com> wrote: > > > > > > > > Hello Rafael, > > > > > > > > Currently, Android reads wakeup sources statistics from > > > > /sys/kernel/debug/wakeup_sources in production environment. This > > > > information is used, for example, to report which wake lock prevents > > > > the device from suspending. > > > > Android's usage of the 'wakeup_sources' from debugfs can is linked at. > > Basically, android's battery stats implementation to plot history for suspend > > blocking wakeup sources over device's boot cycle. This is used both for power > > specific bug reporting but also is one of the stats that will be used towards > > attributing the battery consumption to specific processes over the period of > > time. > > > > Android depended on the out-of-tree /proc/wakelocks before and now relies on > > wakeup_sources debugfs entry heavily for the aforementioned use cases. > > > > > > > > > > Android userspace reading wakeup_sources is not ideal because: > > > > - Debugfs API is not stable, i.e. Android tools built on top of it are > > > > not guaranteed to be backward/forward compatible. > > > > - This file requires debugfs to be mounted, which itself is > > > > undesirable for security reasons. > > > > > > > > To address these problems, we want to contribute a way to expose these > > > > statistics that doesn't depend on debugfs. > > > > > > > > Some initial thoughts/questions: Should we expose the stats in sysfs? > > > > Or maybe implement eBPF-based solution? What do you think? > > > > We are going through Android's out-of-tree kernel dependencies along with > > userspace APIs that are not necessarily considered "stable and forever > > supported" upstream. The debugfs dependencies showed up on our radar as a > > result and so we are wondering if we should worry about changes in debugfs > > interface and hence the question(s) below. > > > > So, can we rely on /d/wakeup_sources to be considered a userspace API and > > hence maintained stable as we do for other /proc and /sys entries? > > > > If yes, then we will go ahead and add tests for this in LTP or > > somewhere else suitable. > > No, debugfs is not ABI. > > > If no, then we would love to hear suggestions for any changes that need to be > > made or we simply just move the debugfs entry into somewhere like > > /sys/power/ ? > > No, moving that entire file from debugfs into sysfs is not an option either. > > The statistics for the wakeup sources associated with devices are already there > under /sys/devices/.../power/ , but I guess you want all wakeup sources? > > That would require adding a kobject to struct wakeup_source and exposing > all of the statistics as separate attributes under it. In which case it would be > good to replace the existing wakeup statistics under /sys/devices/.../power/ > with symbolic links to the attributes under the wakeup_source kobject. Thanks for your input, Rafael! Your suggestion makes sense. I'll work on a patch for this. > > > As a side effect, if the entry moves out of debugfs, Android can run without > > mounting debugfs in production that I assume is a good thing. > > And really Android developers might have thought about this a bit earlier. I'm still learning about kernel development. And Android has made missteps before. So I figured it's a good idea to ask first :) Thanks!
next prev parent reply index Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-06-05 0:23 Tri Vo 2019-06-11 17:31 ` Tri Vo 2019-06-18 20:17 ` Sandeep Patil 2019-06-18 21:23 ` Rafael J. Wysocki 2019-06-18 23:15 ` Tri Vo [this message] 2019-06-18 23:52 ` Joel Fernandes 2019-06-19 8:35 ` Rafael J. Wysocki 2019-06-19 10:33 ` Joel Fernandes 2019-06-19 16:51 ` Sandeep Patil 2019-06-19 16:53 ` Joel Fernandes 2019-06-19 17:07 ` Greg Kroah-Hartman 2019-06-19 18:01 ` Joel Fernandes 2019-06-19 18:31 ` Tri Vo 2019-06-19 18:35 ` Greg Kroah-Hartman 2019-06-19 18:55 ` Joel Fernandes [not found] ` <CAGETcx-ZZRc_jtBws2cFTe1wjiWeBowdqfqOhcCJV_7AUyBEVw@mail.gmail.com> 2019-06-19 20:09 ` Joel Fernandes 2019-06-19 20:40 ` Saravana Kannan 2019-06-19 20:52 ` Joel Fernandes 2019-06-24 1:48 ` Tri Vo 2019-06-24 7:36 ` Greg Kroah-Hartman 2019-06-24 12:27 ` Joel Fernandes 2019-06-24 21:55 ` Rafael J. Wysocki 2019-06-24 22:14 ` Tri Vo
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