Messages in this thread | | | Subject | Re: [PATCH V2] arm64: psci: Reduce waiting time of cpu_psci_cpu_kill() | From | Yunfeng Ye <> | Date | Thu, 17 Oct 2019 22:24:33 +0800 |
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On 2019/10/17 21:54, Sudeep Holla wrote: > On Thu, Oct 17, 2019 at 09:26:15PM +0800, Yunfeng Ye wrote: >> >> >> On 2019/10/16 23:32, Sudeep Holla wrote: >>> On Wed, Oct 09, 2019 at 12:45:16PM +0800, Yunfeng Ye wrote: >>>> If psci_ops.affinity_info() fails, it will sleep 10ms, which will not >>>> take so long in the right case. Use usleep_range() instead of msleep(), >>>> reduce the waiting time, and give a chance to busy wait before sleep. >>>> >>>> Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com> >>>> --- >>>> V1->V2: >>>> - use usleep_range() instead of udelay() after waiting for a while >>>> >>>> arch/arm64/kernel/psci.c | 17 +++++++++++++---- >>>> 1 file changed, 13 insertions(+), 4 deletions(-) >>>> >>>> diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c >>>> index c9f72b2..99b3122 100644 >>>> --- a/arch/arm64/kernel/psci.c >>>> +++ b/arch/arm64/kernel/psci.c >>>> @@ -82,6 +82,7 @@ static void cpu_psci_cpu_die(unsigned int cpu) >>>> static int cpu_psci_cpu_kill(unsigned int cpu) >>>> { >>>> int err, i; >>>> + unsigned long timeout; >>>> >>>> if (!psci_ops.affinity_info) >>>> return 0; >>>> @@ -91,16 +92,24 @@ 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++) { >>>> + i = 0; >>>> + timeout = jiffies + msecs_to_jiffies(100); >>>> + do { >>>> 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); >>>> return 0; >>>> } >>>> >>>> - msleep(10); >>>> - pr_info("Retrying again to check for CPU kill\n"); >>> >>> You dropped this message, any particular reason ? >>> >> When reduce the time interval to 1ms, the print message maybe increase 10 >> times. on the other hand, cpu_psci_cpu_kill() will print message on success >> or failure, which this retry log is not very necessary. of cource, I think >> use pr_info_once() instead of pr_info() is better. >> > > Yes changing it to pr_info_once is better than dropping it as it gives > some indication to the firmware if there's scope for improvement. > >>>> - } >>>> + /* busy-wait max 1ms */ >>>> + if (i++ < 100) { >>>> + cond_resched(); >>>> + udelay(10); >>>> + continue; >>> >>> Why can't it be simple like loop of 100 * msleep(1) instead of loop of >>> 10 * msleep(10). The above initial busy wait for 1 ms looks too much >>> optimised for your setup where it takes 50-500us, what if it take just >>> over 1 ms ? >>> >> msleep() is implemented by jiffies. when HZ=100 or HZ=250, msleep(1) is not >> accurate. so I think usleep_range() is better. 1 ms looks simple and good, but how >> about 100us is better? I refer a function sunxi_mc_smp_cpu_kill(), it use >> usleep_range(50, 100). >> > > Again that's specific to sunxi platforms and may work well. While I agree > msleep(1) may not be accurate, I am still inclined to have a max value > of 1000(i.e. 1ms) for usleep_range. > ok, I will send a new version patch that waiting max 1ms. thanks.
> -- > Regards, > Sudeep > > . >
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