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/
> 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 <yeyunf...@huawei.com>
> ---
> 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.
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
