On 2019/10/18 23:20, Sudeep Holla wrote:
> On Fri, Oct 18, 2019 at 08:46:37PM +0800, Yunfeng Ye wrote:
>> In case like suspend-to-disk and uspend-to-ram, a large number of CPU
>
> s/case/cases/
> s/uspend-to-ram/suspend-to-ram/
>
ok, thanks.
>> cores need to be shut down. At present, the CPU hotplug operation is
>> serialised, and the CPU cores can only be shut down one by one. In this
>> process, if PSCI affinity_info() does not return LEVEL_OFF quickly,
>> cpu_psci_cpu_kill() needs to wait for 10ms. If hundreds of CPU cores
>> need to be shut down, it will take a long time.
>>
>> Normally, there is no need to wait 10ms in cpu_psci_cpu_kill(). So
>> change the wait interval from 10 ms to max 1 ms and use usleep_range()
>> instead of msleep() for more accurate timer.
>>
>> In addition, reducing the time interval will increase the messages
>> output, so remove the "Retry ..." message, instead, put the number of
>> waiting times to the sucessful message.
>>
>> Signed-off-by: Yunfeng Ye <[email protected]>
>> ---
>> v3 -> v4:
>> - using time_before(jiffies, timeout) to check
>> - update the comment as review suggest
>>
>> v2 -> v3:
>> - update the comment
>> - remove the busy-wait logic, modify the loop logic and output message
>>
>> v1 -> v2:
>> - use usleep_range() instead of udelay() after waiting for a while
>> arch/arm64/kernel/psci.c | 14 ++++++++------
>> 1 file changed, 8 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
>> index c9f72b2665f1..77965c3ba477 100644
>> --- a/arch/arm64/kernel/psci.c
>> +++ b/arch/arm64/kernel/psci.c
>> @@ -81,7 +81,8 @@ static void cpu_psci_cpu_die(unsigned int cpu)
>>
>> static int cpu_psci_cpu_kill(unsigned int cpu)
>> {
>> - int err, i;
>> + int err, i = 0;
>> + unsigned long timeout;
>>
>> if (!psci_ops.affinity_info)
>> return 0;
>> @@ -91,16 +92,17 @@ static int cpu_psci_cpu_kill(unsigned int cpu)
>> * while it is dying. So, try again a few times.
>> */
>>
>> - for (i = 0; i < 10; i++) {
>> + timeout = jiffies + msecs_to_jiffies(100);
>> + do {
>> + i++;
>> err = psci_ops.affinity_info(cpu_logical_map(cpu), 0);
>> if (err == PSCI_0_2_AFFINITY_LEVEL_OFF) {
>> - pr_info("CPU%d killed.\n", cpu);
>> + pr_info("CPU%d killed (polled %d times)\n", cpu, i);
>
> We can even drop loop counter completely, track time and log that
> instead of loop counter that doesn't give any indication without looking
> into the code.
>
ok, I will modify as your suggest. thanks.
> start = jiffies, end = start + msecs_to_jiffies(100);
> do {
> ....
> pr_info("CPU%d killed (polled %u ms)\n", cpu,
> jiffies_to_msecs(jiffies - start));
> ....
> } while (time_before(jiffies, end));
>
> Just my preference. Looks good otherwise.
>
> --
> Regards,
> Sudeep
>
>
> .
>
