Re: [PATCH v4 1/5] cpufreq: Don't wait for CPU to going offline to restart governor
From: Viresh Kumar <viresh.kumar@linaro.org>
Date: 2014-08-07 08:54:45
Also in:
linux-arm-msm, lkml
Sorry for the really long delay this time around. I am used to replying within a day normally, and this time it just took so much time. For next time please rebase on latest updates in pm/linux-next as there are few updates there. On 25 July 2014 06:37, Saravana Kannan [off-list ref] wrote:
There's no need to wait for the CPU going down to fully go offline to restart the governor. We can stop the governor, change policy->cpus and immediately restart the governor. This should reduce the time without any CPUfreq monitoring and also help future patches with simplifying the code.
I agree with the idea here, though the $subject can be improved a bit here..
quoted hunk
Signed-off-by: Saravana Kannan <redacted> --- drivers/cpufreq/cpufreq.c | 33 ++++++++++++++++++--------------- 1 file changed, 18 insertions(+), 15 deletions(-)diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 62259d2..ee0eb7b 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c@@ -1390,6 +1390,21 @@ static int __cpufreq_remove_dev_prepare(struct device *dev, cpufreq_driver->stop_cpu(policy); } + down_write(&policy->rwsem); + cpumask_clear_cpu(cpu, policy->cpus); + up_write(&policy->rwsem);
There is a down_read() present early in this routine and we better update this at that place only.
+ if (cpus > 1 && has_target()) {We already have a if (cpus > 1) block, move this there.
quoted hunk
+ ret = __cpufreq_governor(policy, CPUFREQ_GOV_START); + if (!ret) + ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS); + + if (ret) { + pr_err("%s: Failed to start governor\n", __func__); + return ret; + } + } + return 0; }@@ -1410,15 +1425,12 @@ static int __cpufreq_remove_dev_finish(struct device *dev, return -EINVAL; } - down_write(&policy->rwsem); + down_read(&policy->rwsem); cpus = cpumask_weight(policy->cpus); - - if (cpus > 1) - cpumask_clear_cpu(cpu, policy->cpus); - up_write(&policy->rwsem); + up_read(&policy->rwsem); /* If cpu is last user of policy, free policy */ - if (cpus == 1) { + if (cpus == 0) { if (has_target()) { ret = __cpufreq_governor(policy, CPUFREQ_GOV_POLICY_EXIT);@@ -1447,15 +1459,6 @@ static int __cpufreq_remove_dev_finish(struct device *dev, if (!cpufreq_suspended) cpufreq_policy_free(policy); - } else if (has_target()) { - ret = __cpufreq_governor(policy, CPUFREQ_GOV_START); - if (!ret) - ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS); - - if (ret) { - pr_err("%s: Failed to start governor\n", __func__); - return ret; - } }
Also, you must mention in the log about an important change you are making. Don't know if there are any side effects... You are emptying policy->cpus on removal of last CPU of a policy, which wasn't the case earlier.