From mboxrd@z Thu Jan 1 00:00:00 1970 From: shuah Subject: Re: [PATCH for 5.1 3/3] rseq/selftests: Adapt number of threads to the number of detected cpus Date: Fri, 19 Apr 2019 12:57:39 -0600 Message-ID: References: <20190305194755.2602-1-mathieu.desnoyers@efficios.com> <20190305194755.2602-4-mathieu.desnoyers@efficios.com> <20190419103847.GA111210@gmail.com> <1444419838.71.1555677682502.JavaMail.zimbra@efficios.com> <1266612341.87.1555678507226.JavaMail.zimbra@efficios.com> <614774674.134.1555681346941.JavaMail.zimbra@efficios.com> <1863599735.141.1555681723685.JavaMail.zimbra@efficios.com> <6ba0796c-8a96-f797-265c-37bfb9b4bb71@kernel.org> <580328197.148.1555684824260.JavaMail.zimbra@efficios.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <580328197.148.1555684824260.JavaMail.zimbra@efficios.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Mathieu Desnoyers , Ingo Molnar Cc: Thomas Gleixner , linux-kernel , linux-api , Peter Zijlstra , "Paul E . McKenney" , Boqun Feng , Andy Lutomirski , Dave Watson , Paul Turner , Andrew Morton , Russell King , Ingo Molnar , "H. Peter Anvin" , Andi Kleen , Chris Lameter , Ben Maurer , rostedt , Josh Triplett , Linus Torvalds , Catalin Marinas , Will List-Id: linux-api@vger.kernel.org On 4/19/19 8:40 AM, Mathieu Desnoyers wrote: > ----- On Apr 19, 2019, at 10:17 AM, shuah shuah@kernel.org wrote: > >> 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 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 >>>>>>>> Cc: Shuah Khan >>>>>>>> Cc: Thomas Gleixner >>>>>>>> Cc: Joel Fernandes >>>>>>>> Cc: Peter Zijlstra >>>>>>>> Cc: Catalin Marinas >>>>>>>> Cc: Dave Watson >>>>>>>> Cc: Will Deacon >>>>>>>> Cc: Andi Kleen >>>>>>>> Cc: linux-kselftest@vger.kernel.org >>>>>>>> Cc: "H . Peter Anvin" >>>>>>>> Cc: Chris Lameter >>>>>>>> Cc: Russell King >>>>>>>> Cc: Michael Kerrisk >>>>>>>> Cc: "Paul E . McKenney" >>>>>>>> Cc: Paul Turner >>>>>>>> Cc: Boqun Feng >>>>>>>> Cc: Josh Triplett >>>>>>>> Cc: Steven Rostedt >>>>>>>> Cc: Ben Maurer >>>>>>>> Cc: Andy Lutomirski >>>>>>>> Cc: Andrew Morton >>>>>>>> Cc: Linus Torvalds >>>>>>>> --- >>>>>>>> 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) > > It really appears to be an optimization bug in gcc-8. Considering that > bogus compilers are released in the wild, we can hardly justify using > the compiler feature that triggers the bogus behavior, even if it gets > fixed in the future. > > I've prepared a patch that changes the way the __rseq_abi fields are > passed to the inline asm. I pass the address of the __rseq_abi TLS > as a register input operand rather than each individual field as "m" > operand. > > I will submit it in a separate thread. > > By the way, it affects both x86-32 (building with gcc-8 -m32) and x86-64. > Should I drop this patch that is currently in linux-kseltest next? Just confirming if your new patch is supposed to be applied on top of this one or not? thanks, -- Shuah