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 21:26:15 +0800 |
| |
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.
thanks.
>> - } >> + /* 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).
thanks.
> We need more generic solution. > > -- > Regards, > Sudeep > > . >
| |