Re: [PATCH for 5.1 3/3] rseq/selftests: Adapt number of threads to the number of detected cpus

[shuah <shuah@kernel.org>]

On 4/19/19 7:48 AM, Mathieu Desnoyers wrote:
> ----- On Apr 19, 2019, at 9:42 AM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:
> 
>> ----- On Apr 19, 2019, at 8:55 AM, Mathieu Desnoyers
>> mathieu.desnoyers@efficios.com wrote:
>>
>>> ----- On Apr 19, 2019, at 8:41 AM, Mathieu Desnoyers
>>> mathieu.desnoyers@efficios.com wrote:
>>>
>>>> ----- On Apr 19, 2019, at 6:38 AM, Ingo Molnar mingo@kernel.org wrote:
>>>>
>>>>> * Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:
>>>>>
>>>>>> On smaller systems, running a test with 200 threads can take a long
>>>>>> time on machines with smaller number of CPUs.
>>>>>>
>>>>>> Detect the number of online cpus at test runtime, and multiply that
>>>>>> by 6 to have 6 rseq threads per cpu preempting each other.
>>>>>>
>>>>>> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
>>>>>> Cc: Shuah Khan <shuah@kernel.org>
>>>>>> Cc: Thomas Gleixner <tglx@linutronix.de>
>>>>>> Cc: Joel Fernandes <joelaf@google.com>
>>>>>> Cc: Peter Zijlstra <peterz@infradead.org>
>>>>>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>>>>>> Cc: Dave Watson <davejwatson@fb.com>
>>>>>> Cc: Will Deacon <will.deacon@arm.com>
>>>>>> Cc: Andi Kleen <andi@firstfloor.org>
>>>>>> Cc: linux-kselftest@vger.kernel.org
>>>>>> Cc: "H . Peter Anvin" <hpa@zytor.com>
>>>>>> Cc: Chris Lameter <cl@linux.com>
>>>>>> Cc: Russell King <linux@arm.linux.org.uk>
>>>>>> Cc: Michael Kerrisk <mtk.manpages@gmail.com>
>>>>>> Cc: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>
>>>>>> Cc: Paul Turner <pjt@google.com>
>>>>>> Cc: Boqun Feng <boqun.feng@gmail.com>
>>>>>> Cc: Josh Triplett <josh@joshtriplett.org>
>>>>>> Cc: Steven Rostedt <rostedt@goodmis.org>
>>>>>> Cc: Ben Maurer <bmaurer@fb.com>
>>>>>> Cc: Andy Lutomirski <luto@amacapital.net>
>>>>>> Cc: Andrew Morton <akpm@linux-foundation.org>
>>>>>> Cc: Linus Torvalds <torvalds@linux-foundation.org>
>>>>>> ---
>>>>>>   tools/testing/selftests/rseq/run_param_test.sh | 7 +++++--
>>>>>>   1 file changed, 5 insertions(+), 2 deletions(-)
>>>>>>
>>>>>> diff --git a/tools/testing/selftests/rseq/run_param_test.sh
>>>>>> b/tools/testing/selftests/rseq/run_param_test.sh
>>>>>> index 3acd6d75ff9f..e426304fd4a0 100755
>>>>>> --- a/tools/testing/selftests/rseq/run_param_test.sh
>>>>>> +++ b/tools/testing/selftests/rseq/run_param_test.sh
>>>>>> @@ -1,6 +1,8 @@
>>>>>>   #!/bin/bash
>>>>>>   # SPDX-License-Identifier: GPL-2.0+ or MIT
>>>>>>   
>>>>>> +NR_CPUS=`grep '^processor' /proc/cpuinfo | wc -l`
>>>>>> +
>>>>>>   EXTRA_ARGS=${@}
>>>>>>   
>>>>>>   OLDIFS="$IFS"
>>>>>> @@ -28,15 +30,16 @@ IFS="$OLDIFS"
>>>>>>   
>>>>>>   REPS=1000
>>>>>>   SLOW_REPS=100
>>>>>> +NR_THREADS=$((6*${NR_CPUS}))
>>>>>>   
>>>>>>   function do_tests()
>>>>>>   {
>>>>>>   	local i=0
>>>>>>   	while [ "$i" -lt "${#TEST_LIST[@]}" ]; do
>>>>>>   		echo "Running test ${TEST_NAME[$i]}"
>>>>>> -		./param_test ${TEST_LIST[$i]} -r ${REPS} ${@} ${EXTRA_ARGS} || exit 1
>>>>>> +		./param_test ${TEST_LIST[$i]} -r ${REPS} -t ${NR_THREADS} ${@} ${EXTRA_ARGS}
>>>>>> || exit 1
>>>>>>   		echo "Running compare-twice test ${TEST_NAME[$i]}"
>>>>>> -		./param_test_compare_twice ${TEST_LIST[$i]} -r ${REPS} ${@} ${EXTRA_ARGS} ||
>>>>>> exit 1
>>>>>> +		./param_test_compare_twice ${TEST_LIST[$i]} -r ${REPS} -t ${NR_THREADS} ${@}
>>>>>> ${EXTRA_ARGS} || exit 1
>>>>>>   		let "i++"
>>>>>>   	done
>>>>>>   }
>>>>>
>>>>> BTW., when trying to build the rseq self-tests I get this build failure:
>>>>>
>>>>>   dagon:~/tip/tools/testing/selftests/rseq> make
>>>>>   gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L./ -Wl,-rpath=./ -shared
>>>>>   -fPIC rseq.c -lpthread -o
>>>>>   /home/mingo/tip/tools/testing/selftests/rseq/librseq.so
>>>>>   gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L./ -Wl,-rpath=./ basic_test.c
>>>>>   -lpthread -lrseq -o /home/mingo/tip/tools/testing/selftests/rseq/basic_test
>>>>>   gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L./ -Wl,-rpath=./
>>>>>   basic_percpu_ops_test.c -lpthread -lrseq -o
>>>>>   /home/mingo/tip/tools/testing/selftests/rseq/basic_percpu_ops_test
>>>>>   /usr/bin/ld: /tmp/ccuHTWnZ.o: in function `rseq_cmpeqv_storev':
>>>>>   /home/mingo/tip/tools/testing/selftests/rseq/./rseq-x86.h:84: undefined
>>>>>   reference to `.L8'
>>>>>   /usr/bin/ld: /home/mingo/tip/tools/testing/selftests/rseq/./rseq-x86.h:84:
>>>>>   undefined reference to `.L49'
>>>>>   /usr/bin/ld: /tmp/ccuHTWnZ.o: in function `rseq_cmpnev_storeoffp_load':
>>>>>   /home/mingo/tip/tools/testing/selftests/rseq/./rseq-x86.h:141: undefined
>>>>>   reference to `.L57'
>>>>>   /usr/bin/ld: /tmp/ccuHTWnZ.o:(__rseq_failure+0x8): undefined reference to `.L8'
>>>>>   /usr/bin/ld: /tmp/ccuHTWnZ.o:(__rseq_failure+0x14): undefined reference to
>>>>>   `.L49'
>>>>>   /usr/bin/ld: /tmp/ccuHTWnZ.o:(__rseq_failure+0x20): undefined reference to
>>>>>   `.L55'
>>>>>   collect2: error: ld returned 1 exit status
>>>>>   make: *** [Makefile:22:
>>>>>   /home/mingo/tip/tools/testing/selftests/rseq/basic_percpu_ops_test] Error 1
>>>>>
>>>>> Is this a known problem, or do I miss something from my build environment
>>>>> perhaps? Vanilla 64-bit Ubuntu 18.10 (Cosmic).
>>>>
>>>> It works fine with gcc-7 (gcc version 7.3.0 (Ubuntu 7.3.0-16ubuntu3))
>>>> but indeed I get the same failure with gcc-8 (gcc version 8.0.1 20180414
>>>> (experimental) [trunk revision 259383] (Ubuntu 8-20180414-1ubuntu2)).
>>>>
>>>> Thanks for reporting! I will investigate.
>>>
>>> It looks like gcc-8 optimize away the target of asm goto labels when
>>> there are more than one of them on x86-64. I'll try to come up with
>>> a simpler reproducer.
>>
>> It appears to be related to gcc-8 mishandling combination of
>> asm goto and thread-local storage input operands on x86-64.
>> Here is a simple reproducer:
>>
>> __thread int var;
>>   
>> static int fct(void)
>> {
>>         asm goto (      "jmp %l[testlabel]\n\t"
>>                         : : [var] "m" (var) : : testlabel);
>>         return 0;
>> testlabel:
> 
> FWIW, if I add an empty
> 
>     asm volatile ("");
> 
> here after the label, gcc-8 -O2 builds "something" which is
> a bogus assembler (an endless loop) :
> 
> main:
> .LFB24:
>          .cfi_startproc
> .L2:
>          subq    $8, %rsp
>          .cfi_def_cfa_offset 16
> #APP
> # 6 "test-asm-goto.c" 1
>          jmp .L2
> 
> # 0 "" 2
> #NO_APP
>          movl    %fs:var@tpoff, %edx
>          leaq    .LC0(%rip), %rsi
>          movl    $1, %edi
>          xorl    %eax, %eax
>          call    __printf_chk@PLT
>          xorl    %eax, %eax
>          addq    $8, %rsp
>          .cfi_def_cfa_offset 8
>          ret
>          .cfi_endproc
> 
> Thoughts ?
> 

Didn't see problems when I tested it before applying it to
linux-kselftest next.

I have gcc version 7.3.0 (Ubuntu 7.3.0-27ubuntu1~18.04)

thanks,
-- Shuah