| Message ID | 9df267db-e647-a81d-16bb-b8bfb06c2624@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [V2] arm64: psci: Reduce waiting time of cpu_psci_cpu_kill() | expand |
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 ? > - } > + /* 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 ? We need more generic solution. -- Regards, Sudeep
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 > > . >
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. -- Regards, Sudeep
From: Yunfeng Ye > Sent: 17 October 2019 14:26 ... > >> - 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. Maybe you should print in on (say) the 10th time around the loop. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
On 2019/10/17 22:00, David Laight wrote: > From: Yunfeng Ye >> Sent: 17 October 2019 14:26 > ... >>>> - 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. > > Maybe you should print in on (say) the 10th time around the loop. > Can it like this: pr_info("CPU%d killed with %d loops.\n", cpu, loops); If put the number of waiting times in the successful printing message, it is not necessary to print the "Retrying ..." message. thanks. > David > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales) >
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 > > . >
From: Yunfeng Ye > Sent: 17 October 2019 15:20 > On 2019/10/17 22:00, David Laight wrote: > > From: Yunfeng Ye > >> Sent: 17 October 2019 14:26 > > ... > >>>> - 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. > > > > Maybe you should print in on (say) the 10th time around the loop. > > > Can it like this: > pr_info("CPU%d killed with %d loops.\n", cpu, loops); > > If put the number of waiting times in the successful printing message, it is > not necessary to print the "Retrying ..." message. That depends on whether you want to know how long it took or why the system is 'stuck'. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
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"); - } + /* busy-wait max 1ms */ + if (i++ < 100) { + cond_resched(); + udelay(10); + continue; + } + + usleep_range(100, 1000); + } while (time_before(jiffies, timeout)); pr_warn("CPU%d may not have shut down cleanly (AFFINITY_INFO reports %d)\n", cpu, err);
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(-)