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Message-ID: <20191018114529.GA15116@bogus>
Date: Fri, 18 Oct 2019 12:45:29 +0100
From: Sudeep Holla <sudeep.holla@....com>
To: Yunfeng Ye <yeyunfeng@...wei.com>
Cc: catalin.marinas@....com, will@...nel.org,
kstewart@...uxfoundation.org, gregkh@...uxfoundation.org,
lorenzo.pieralisi@....com, tglx@...utronix.de,
David.Laight@...LAB.COM, ard.biesheuvel@...aro.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
"hushiyuan@...wei.com" <hushiyuan@...wei.com>, wuyun.wu@...wei.com,
"linfeilong@...wei.com" <linfeilong@...wei.com>
Subject: Re: [PATCH V3] arm64: psci: Reduce waiting time for
cpu_psci_cpu_kill()
On Fri, Oct 18, 2019 at 07:24:14PM +0800, Yunfeng Ye wrote:
> In a case like suspend-to-disk, a large number of CPU cores need to be
Add suspend-to-ram also to list, i.e.
"In case like suspend-to-disk and suspend-to-ram, a large number..."
> 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, it is no need to wait 10ms in cpu_psci_cpu_kill(). So change
s/it is/there is/
> the wait interval from 10 ms to max 1 ms and use usleep_range() instead
> of msleep() for more accurate schedule.
>
s/for more accurate schedule/for more accurate timer/
> In addition, reduce the time interval will increase the messages output,
s/reduce/reducing/
> so remove the "Retry ..." message, instead, put the number of waiting
> times to the sucessful message.
>
> Signed-off-by: Yunfeng Ye <yeyunfeng@...wei.com>
> ---
> 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 | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
> index c9f72b2665f1..00b8c0825a08 100644
> --- a/arch/arm64/kernel/psci.c
> +++ b/arch/arm64/kernel/psci.c
> @@ -91,15 +91,14 @@ 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++) {
> + for (i = 0; i < 100; 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 by waiting %d loops.\n", cpu, i);
> return 0;
> }
>
> - msleep(10);
> - pr_info("Retrying again to check for CPU kill\n");
> + usleep_range(100, 1000);
Since usleep_range can return anytime between 100us to 1ms, does it make
sense to check for (time_before(jiffies, timeout)) you had in v2 ?
--
Regards,
Sudeep
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