[PATCH] selftests/net: skip msg_zerocopy test if we have less than 4 CPUs

[PATCH] selftests/net: skip msg_zerocopy test if we have less than 4 CPUs

[Colin King]

From: Colin Ian King <colin.king@canonical.com>

The current test will exit with a failure if it cannot set affinity on
specific CPUs which is problematic when running this on single CPU
systems. Add a check for the number of CPUs and skip the test if
the CPU requirement is not met.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 tools/testing/selftests/net/msg_zerocopy.sh | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/testing/selftests/net/msg_zerocopy.sh b/tools/testing/selftests/net/msg_zerocopy.sh
index 825ffec85cea..97bc527e1297 100755
--- a/tools/testing/selftests/net/msg_zerocopy.sh
+++ b/tools/testing/selftests/net/msg_zerocopy.sh
@@ -21,6 +21,11 @@ readonly DADDR6='fd::2'
 
 readonly path_sysctl_mem="net.core.optmem_max"
 
+if [[ $(nproc) -lt 4 ]]; then
+	echo "SKIP: test requires at least 4 CPUs"
+	exit 4
+fi
+
 # No arguments: automated test
 if [[ "$#" -eq "0" ]]; then
 	$0 4 tcp -t 1
-- 
2.27.0

Re: [PATCH] selftests/net: skip msg_zerocopy test if we have less than 4 CPUs

[David Miller]

From: Colin King <colin.king@canonical.com>
Date: Tue,  4 Aug 2020 13:30:12 +0100

> From: Colin Ian King <colin.king@canonical.com>
> 
> The current test will exit with a failure if it cannot set affinity on
> specific CPUs which is problematic when running this on single CPU
> systems. Add a check for the number of CPUs and skip the test if
> the CPU requirement is not met.
> 
> Signed-off-by: Colin Ian King <colin.king@canonical.com>

Willem, please review.

Re: [PATCH] selftests/net: skip msg_zerocopy test if we have less than 4 CPUs

[Eric Dumazet]

On 8/4/20 5:30 AM, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> The current test will exit with a failure if it cannot set affinity on
> specific CPUs which is problematic when running this on single CPU
> systems. Add a check for the number of CPUs and skip the test if
> the CPU requirement is not met.
> 
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>  tools/testing/selftests/net/msg_zerocopy.sh | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/tools/testing/selftests/net/msg_zerocopy.sh b/tools/testing/selftests/net/msg_zerocopy.sh
> index 825ffec85cea..97bc527e1297 100755
> --- a/tools/testing/selftests/net/msg_zerocopy.sh
> +++ b/tools/testing/selftests/net/msg_zerocopy.sh
> @@ -21,6 +21,11 @@ readonly DADDR6='fd::2'
>  
>  readonly path_sysctl_mem="net.core.optmem_max"
>  
> +if [[ $(nproc) -lt 4 ]]; then
> +	echo "SKIP: test requires at least 4 CPUs"
> +	exit 4
> +fi
> +
>  # No arguments: automated test
>  if [[ "$#" -eq "0" ]]; then
>  	$0 4 tcp -t 1
> 

Test explicitly uses CPU 2 and 3, right ?

nproc could be 500, yet cpu 2 or 3 could be offline

# cat /sys/devices/system/cpu/cpu3/online
0
# echo $(nproc)
71

Re: [PATCH] selftests/net: skip msg_zerocopy test if we have less than 4 CPUs

[Willem de Bruijn]

On Wed, Aug 5, 2020 at 2:54 AM Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
>
>
> On 8/4/20 5:30 AM, Colin King wrote:
> > From: Colin Ian King <colin.king@canonical.com>
> >
> > The current test will exit with a failure if it cannot set affinity on
> > specific CPUs which is problematic when running this on single CPU
> > systems. Add a check for the number of CPUs and skip the test if
> > the CPU requirement is not met.
> >
> > Signed-off-by: Colin Ian King <colin.king@canonical.com>
> > ---
> >  tools/testing/selftests/net/msg_zerocopy.sh | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/tools/testing/selftests/net/msg_zerocopy.sh b/tools/testing/selftests/net/msg_zerocopy.sh
> > index 825ffec85cea..97bc527e1297 100755
> > --- a/tools/testing/selftests/net/msg_zerocopy.sh
> > +++ b/tools/testing/selftests/net/msg_zerocopy.sh
> > @@ -21,6 +21,11 @@ readonly DADDR6='fd::2'
> >
> >  readonly path_sysctl_mem="net.core.optmem_max"
> >
> > +if [[ $(nproc) -lt 4 ]]; then
> > +     echo "SKIP: test requires at least 4 CPUs"
> > +     exit 4
> > +fi
> > +
> >  # No arguments: automated test
> >  if [[ "$#" -eq "0" ]]; then
> >       $0 4 tcp -t 1
> >
>
> Test explicitly uses CPU 2 and 3, right ?
>
> nproc could be 500, yet cpu 2 or 3 could be offline
>
> # cat /sys/devices/system/cpu/cpu3/online
> 0
> # echo $(nproc)
> 71

The cpu affinity is only set to bring some stability across runs.

The test does not actually verify that a run with zerocopy is some
factor faster than without, as that factor is hard to choose across
all platforms. As a result the automated run mainly gives code coverage.

It's preferable to always run. And on sched_setaffinity failure log a
message about possible jitter and continue. I can send that patch, if
the approach sounds good.

Re: [PATCH] selftests/net: skip msg_zerocopy test if we have less than 4 CPUs

[Colin Ian King]

On 05/08/2020 09:06, Willem de Bruijn wrote:
> On Wed, Aug 5, 2020 at 2:54 AM Eric Dumazet <eric.dumazet@gmail.com> wrote:
>>
>>
>>
>> On 8/4/20 5:30 AM, Colin King wrote:
>>> From: Colin Ian King <colin.king@canonical.com>
>>>
>>> The current test will exit with a failure if it cannot set affinity on
>>> specific CPUs which is problematic when running this on single CPU
>>> systems. Add a check for the number of CPUs and skip the test if
>>> the CPU requirement is not met.
>>>
>>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>>> ---
>>>  tools/testing/selftests/net/msg_zerocopy.sh | 5 +++++
>>>  1 file changed, 5 insertions(+)
>>>
>>> diff --git a/tools/testing/selftests/net/msg_zerocopy.sh b/tools/testing/selftests/net/msg_zerocopy.sh
>>> index 825ffec85cea..97bc527e1297 100755
>>> --- a/tools/testing/selftests/net/msg_zerocopy.sh
>>> +++ b/tools/testing/selftests/net/msg_zerocopy.sh
>>> @@ -21,6 +21,11 @@ readonly DADDR6='fd::2'
>>>
>>>  readonly path_sysctl_mem="net.core.optmem_max"
>>>
>>> +if [[ $(nproc) -lt 4 ]]; then
>>> +     echo "SKIP: test requires at least 4 CPUs"
>>> +     exit 4
>>> +fi
>>> +
>>>  # No arguments: automated test
>>>  if [[ "$#" -eq "0" ]]; then
>>>       $0 4 tcp -t 1
>>>
>>
>> Test explicitly uses CPU 2 and 3, right ?
>>
>> nproc could be 500, yet cpu 2 or 3 could be offline
>>
>> # cat /sys/devices/system/cpu/cpu3/online
>> 0
>> # echo $(nproc)
>> 71
> 
> The cpu affinity is only set to bring some stability across runs.
> 
> The test does not actually verify that a run with zerocopy is some
> factor faster than without, as that factor is hard to choose across
> all platforms. As a result the automated run mainly gives code coverage.
> 
> It's preferable to always run. And on sched_setaffinity failure log a
> message about possible jitter and continue. I can send that patch, if
> the approach sounds good.
> 
That's sounds preferable to my bad fix for sure :-)

Colin

Re: [PATCH] selftests/net: skip msg_zerocopy test if we have less than 4 CPUs

[Willem de Bruijn]

On Wed, Aug 5, 2020 at 10:22 AM Colin Ian King <colin.king@canonical.com> wrote:
>
> On 05/08/2020 09:06, Willem de Bruijn wrote:
> > On Wed, Aug 5, 2020 at 2:54 AM Eric Dumazet <eric.dumazet@gmail.com> wrote:
> >>
> >>
> >>
> >> On 8/4/20 5:30 AM, Colin King wrote:
> >>> From: Colin Ian King <colin.king@canonical.com>
> >>>
> >>> The current test will exit with a failure if it cannot set affinity on
> >>> specific CPUs which is problematic when running this on single CPU
> >>> systems. Add a check for the number of CPUs and skip the test if
> >>> the CPU requirement is not met.
> >>>
> >>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> >>> ---
> >>>  tools/testing/selftests/net/msg_zerocopy.sh | 5 +++++
> >>>  1 file changed, 5 insertions(+)
> >>>
> >>> diff --git a/tools/testing/selftests/net/msg_zerocopy.sh b/tools/testing/selftests/net/msg_zerocopy.sh
> >>> index 825ffec85cea..97bc527e1297 100755
> >>> --- a/tools/testing/selftests/net/msg_zerocopy.sh
> >>> +++ b/tools/testing/selftests/net/msg_zerocopy.sh
> >>> @@ -21,6 +21,11 @@ readonly DADDR6='fd::2'
> >>>
> >>>  readonly path_sysctl_mem="net.core.optmem_max"
> >>>
> >>> +if [[ $(nproc) -lt 4 ]]; then
> >>> +     echo "SKIP: test requires at least 4 CPUs"
> >>> +     exit 4
> >>> +fi
> >>> +
> >>>  # No arguments: automated test
> >>>  if [[ "$#" -eq "0" ]]; then
> >>>       $0 4 tcp -t 1
> >>>
> >>
> >> Test explicitly uses CPU 2 and 3, right ?
> >>
> >> nproc could be 500, yet cpu 2 or 3 could be offline
> >>
> >> # cat /sys/devices/system/cpu/cpu3/online
> >> 0
> >> # echo $(nproc)
> >> 71
> >
> > The cpu affinity is only set to bring some stability across runs.
> >
> > The test does not actually verify that a run with zerocopy is some
> > factor faster than without, as that factor is hard to choose across
> > all platforms. As a result the automated run mainly gives code coverage.
> >
> > It's preferable to always run. And on sched_setaffinity failure log a
> > message about possible jitter and continue. I can send that patch, if
> > the approach sounds good.
> >
> That's sounds preferable to my bad fix for sure :-)

Certainly not a bad fix! Thanks for addressing the issue. Alternative
approach at

http://patchwork.ozlabs.org/project/netdev/patch/20200805084045.1549492-1-willemdebruijn.kernel@gmail.com/

Re: [PATCH] selftests/net: skip msg_zerocopy test if we have less than 4 CPUs

[Colin Ian King]

On 05/08/2020 09:44, Willem de Bruijn wrote:
> On Wed, Aug 5, 2020 at 10:22 AM Colin Ian King <colin.king@canonical.com> wrote:
>>
>> On 05/08/2020 09:06, Willem de Bruijn wrote:
>>> On Wed, Aug 5, 2020 at 2:54 AM Eric Dumazet <eric.dumazet@gmail.com> wrote:
>>>>
>>>>
>>>>
>>>> On 8/4/20 5:30 AM, Colin King wrote:
>>>>> From: Colin Ian King <colin.king@canonical.com>
>>>>>
>>>>> The current test will exit with a failure if it cannot set affinity on
>>>>> specific CPUs which is problematic when running this on single CPU
>>>>> systems. Add a check for the number of CPUs and skip the test if
>>>>> the CPU requirement is not met.
>>>>>
>>>>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>>>>> ---
>>>>>  tools/testing/selftests/net/msg_zerocopy.sh | 5 +++++
>>>>>  1 file changed, 5 insertions(+)
>>>>>
>>>>> diff --git a/tools/testing/selftests/net/msg_zerocopy.sh b/tools/testing/selftests/net/msg_zerocopy.sh
>>>>> index 825ffec85cea..97bc527e1297 100755
>>>>> --- a/tools/testing/selftests/net/msg_zerocopy.sh
>>>>> +++ b/tools/testing/selftests/net/msg_zerocopy.sh
>>>>> @@ -21,6 +21,11 @@ readonly DADDR6='fd::2'
>>>>>
>>>>>  readonly path_sysctl_mem="net.core.optmem_max"
>>>>>
>>>>> +if [[ $(nproc) -lt 4 ]]; then
>>>>> +     echo "SKIP: test requires at least 4 CPUs"
>>>>> +     exit 4
>>>>> +fi
>>>>> +
>>>>>  # No arguments: automated test
>>>>>  if [[ "$#" -eq "0" ]]; then
>>>>>       $0 4 tcp -t 1
>>>>>
>>>>
>>>> Test explicitly uses CPU 2 and 3, right ?
>>>>
>>>> nproc could be 500, yet cpu 2 or 3 could be offline
>>>>
>>>> # cat /sys/devices/system/cpu/cpu3/online
>>>> 0
>>>> # echo $(nproc)
>>>> 71
>>>
>>> The cpu affinity is only set to bring some stability across runs.
>>>
>>> The test does not actually verify that a run with zerocopy is some
>>> factor faster than without, as that factor is hard to choose across
>>> all platforms. As a result the automated run mainly gives code coverage.
>>>
>>> It's preferable to always run. And on sched_setaffinity failure log a
>>> message about possible jitter and continue. I can send that patch, if
>>> the approach sounds good.
>>>
>> That's sounds preferable to my bad fix for sure :-)
> 
> Certainly not a bad fix! Thanks for addressing the issue. Alternative
> approach at
> 
> http://patchwork.ozlabs.org/project/netdev/patch/20200805084045.1549492-1-willemdebruijn.kernel@gmail.com/
> 
Thanks, you solution is good for my testing requirements

Acked-by: Colin Ian King <colin.king@canonical.com>