Re: [PATCH 00/18] cpufreq: don't loose cpufreq history on CPU hotplug

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

On Tuesday, January 27, 2015 02:06:06 PM Viresh Kumar wrote:
> Hi Rafael,
> 
> The aim of this series is to stop managing cpufreq sysfs directories on CPU
> hotplugs.
> 
> This issue has been raised multiple times earlier, the latest being tried by
> Saravana. While working on the $Subject thread, I did lots of cleanups, most of
> which are already pushed by you.
> 
> The two remaining ones are added to this series..
> 
> Currently on removal of a 'cpu != policy->cpu', we remove its sysfs directories
> by removing the soft-link. And on removal of policy->cpu, we migrate the sysfs
> directories to the next cpu. But if policy->cpu was the last CPU, we remove the
> policy completely and allocate it again as soon as the CPUs come back. This has
> shortcomings:
> 
> - Code Complexity
> - Slower hotplug
> - sysfs file permissions are reset after all policy->cpus are offlined
> - CPUFreq stats history lost after all policy->cpus are offlined
> - Special management of sysfs stuff during suspend/resume
> 
> 
> To make things simple we stop playing with sysfs files unless the driver is
> getting removed. Also the policy is kept intact to be used later.
> 
> First few patches provide a clean base for others *more important* patches.
> 
> Rebased-over: your bleeding edge branch as there were dependencies on my earlier
> patches.
> 
> Pushed here:
> 
> git://git.linaro.org/people/viresh.kumar/linux.git cpufreq/core/sysfs
> 
> @Saravana/Prarit: It would be good if you can provide your feedback/reviews on
> this. Thanks in advance.
> 
> @Saravana: Few patches might look very similar to what you have done, please add
> your SOB for those :)
> 
> --
> viresh
> 
> Viresh Kumar (18):
>   cpufreq: Drop cpufreq_disabled() check from cpufreq_cpu_{get|put}()
>   cpufreq: Create for_each_policy()
>   cpufreq: Create for_each_governor()
>   cpufreq: Manage fallback policies in a list
>   cpufreq: Manage governor usage history with 'policy->last_governor'
>   cpufreq: Reuse policy list instead of per-cpu variable
>     'cpufreq_cpu_data'
>   cpufreq: Drop (now) useless check 'cpu > nr_cpu_ids'
>   cpufreq: Add doc style comment about cpufreq_cpu_{get|put}()
>   cpufreq: Mark policy->governor = NULL for fallback policies
>   cpufreq: Don't allow updating inactive-policies from sysfs
>   cpufreq: Track cpu managing sysfs kobjects separately
>   cpufreq: Stop migrating sysfs files on hotplug
>   cpufreq: Keep a single path for adding managed CPUs
>   cpufreq: Remove cpufreq_update_policy()
>   cpufreq: Initialize policy->kobj while allocating policy
>   cpufreq: Call cpufreq_policy_put_kobj() from cpufreq_policy_free()
>   cpufreq: Restart governor as soon as possible
>   cpufreq: Merge __cpufreq_add_dev() and cpufreq_add_dev()
> 
>  drivers/cpufreq/cpufreq.c | 551 +++++++++++++++++++++++-----------------------
>  include/linux/cpufreq.h   |  10 +-
>  2 files changed, 287 insertions(+), 274 deletions(-)

The first three patches I have no problems with, so I've queued them up for 3.20.


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.