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Tue, 22 Sep 2026 15:37:14 +0000 (GMT) Received: from [9.111.22.84] (unknown [9.111.22.84]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 22 Sep 2026 15:37:14 +0000 (GMT) Message-ID: Date: Tue, 22 Sep 2026 17:37:14 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 00/11] s390: More this_cpu_*() changes To: Heiko Carstens , Alexander Gordeev , Sven Schnelle , Vasily Gorbik , Christian Borntraeger , Peter Zijlstra , Mark Rutland , Juergen Christ , Ilya Leoshkevich Cc: linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org References: <20260921155806.2447506-1-hca@linux.ibm.com> Content-Language: en-US From: Mete Durlu In-Reply-To: <20260921155806.2447506-1-hca@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 6S3gsGywxpjOubl5YlqYT1VEntfNj09c X-Proofpoint-Spam-Info: AW1haW4tMjYwOTIyMDIyNyBTYWx0ZWRfX9wYK9s2Ubhyo Wi+5Re6iB+Xgxy7uuOqUc7fzz+dnG0w4TdQ4OavOAAOREcg255d5+yfvwE62B8imaGH4OLinVgu 3IIJn1zFlQuhVabHjMLmFQIdjuu470M= X-Authority-Analysis: v=2.4 cv=FLiOVOos c=1 sm=1 tr=0 ts=6ab2a0af cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VwQbUJbxAAAA:8 a=7CQSdrXTAAAA:8 a=s7ObvvvYnUrjyN0Krc8A:9 a=QEXdDO2ut3YA:10 a=a-qgeE7W1pNrGK8U0ZQC:22 X-Proofpoint-GUID: 6S3gsGywxpjOubl5YlqYT1VEntfNj09c X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTIyMDIyNyBTYWx0ZWRfX6E80gNfZXN2h lgugKO6eKafQFl21wj4jdB241EcsI+xdIGUHb3hhyCOG9zrDim7dVQEPXGSlSO0kRRCoOY1mcrx 0zybM9cMF/0MnaCSp0QWGAbyiNlJOYBvMfUukNxKUOwhlITGgEODayYgWLKfLmwXvD1HRNVTFdm UPpoRTRsrIGEz1UvBKRkM3F5mHA+Ha1pK8vxCNW7YuwjtfCbLRcmm1Ac1rkfcuZ8Wb5JYu4omgu 5PsM9d2H8Ucuu70Cp6m6ICeNuAWNIEjdQZZbnQ4f7fuxva7jRY5yKR/QHRgUwW9aPmUnRHAM+Ox g9DavEg/DHiHyajz9WFH1KT7kobaNb56pLJp+g+FIeXYsrINJ3npiX487LinmussskzkO1CxgfC B6f7/YpkB/4lGN/3BsU0qmSrVip74ZUdjiWxynxaCD4gC2jJMJs2Xh2IxO/vhKL9N9MK7YmwRID HA+p/bHRJr0hYYgn8UA== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-09-22_02,2026-09-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 impostorscore=0 phishscore=0 spamscore=0 clxscore=1011 suspectscore=0 bulkscore=0 lowpriorityscore=0 priorityscore=1501 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609220227 On 21/09/2026 17:57, Heiko Carstens wrote: [..snip..] > v1: > Most of this is only about cleaning up the percpu code after preemptible > this_cpu_*() operations have been implemented. The first ten patches are > all more or less trivial cleanup patches trying to make the code shorter > and more readable. > > The only non-trivial patch is the last one, which converts s390's > this_cpu_*() operations to use a similar scheme like Mark Rutland > provided it for arm64 [1]. This allows to simplify the irq entry and exit > path, however at the cost of slightly worse code for this_cpu_*() > operations. > > The simplified irq entry and exit code seems to be worth it. Usable > performance numbers are not available yet, however I don't expect big > difference to before. > > [1] https://lore.kernel.org/all/20260904161758.376504-1-mark.rutland@arm.com/ > > Thanks, > Heiko > > Heiko Carstens (11): > s390/percpu: Fix comment typo > s390/percpu: Add sanity check to GEN_MVIY macro > s390/lowcore: Remove _AC() from LOWCORE_ALT_ADDRESS > s390/percpu: Let MVIY_PERCPU() calculate alternative displacement > s390/percpu/lowcore: Add and use LC_PERCPU lowcore offset defines > s390/percpu: Rename inline assembly symbolic names > s390/percpu: Use __PCPU_BEGIN() and __PCPU_END() for inline assemblies > s390/percpu: Use percpu code section for this_cpu_cmpxchg128() > s390/percpu: Use percpu code section for this_cpu_xchg() > s390/percpu: Use percpu code section for this_cpu_cmpxchg() > s390/percpu: Rework to simplify percpu_entry() and percpu_exit() > > arch/s390/include/asm/entry-percpu.h | 71 ++---- > arch/s390/include/asm/lowcore.h | 5 +- > arch/s390/include/asm/percpu.h | 354 +++++++++++++++++---------- > arch/s390/kernel/irq.c | 10 +- > arch/s390/kernel/nmi.c | 4 +- > arch/s390/kernel/traps.c | 4 +- > 6 files changed, 248 insertions(+), 200 deletions(-) > Hi all, I did some benchmarking for this patch series. Used a shared LPAR with 24 CPUs (12 cores w SMT2). Base commit: f0100363d8c3 ("Merge tag 'xfs-fixes-7.3-rc5' of gitolite.kernel.org:/pub/scm/fs/xfs/xfs-linux") Some of the benchmark runs show +-5% standard deviation which can be attributed to s390 being a virtualized system. Each run has been repeated five times to circumvent the effects of standard deviation. (In the odd case where baseline has -5% and patched run has +5% deviation, the comparison can show ~+10% improvements which is highly misleading). Overall, the benchmarks do not show any real difference between baseline and patched kernels; 1-) Hackbench ======================================================================== Repeated hackbench runs with different group and fd count combinations; [1, 2, 4, 8] $ hackbench -T -p -l $loops -g $g -f $f no real difference. 2-) Stress-ng ======================================================================== Repeated stress-ng runs with range of stressors: [6, $(nproc)] # 3d matrix operations $ stress-ng --matrix-3d $cpu --matrix-3d-method mult --timeout 10 # repeated mmap() and munmap() operations and also writing to the # allocated memory. $ stress-ng --vm $cpu --vm-bytes 128M --timeout 10 # starts workers that each fork off 32 child processes. Each child # tries to allocate some memory. Child processes use madvise and memset # to produce VM activity. $ stress-ng --mmapfork $cpu --mmapfork-bytes 128M --timeout 10 no real difference. 3-) Openblas Benchmark ======================================================================== Repeated matrix operations with different size of 3d matrices. $ make -j$(nproc) \ USE_OPENMP=1 \ NUM_THREADS=$(nproc)\ NOFORTRAN=1 > /dev/null 2>&1 $ make -C benchmark sgemm.goto \ USE_OPENMP=1 \ NUM_THREADS=$(nproc) \ NOFORTRAN=1 > /dev/null 2>&1 $ OPENBLAS_LOOPS=50 sgemm.goto no real difference between runs. 4-) Compiling kernel ======================================================================== Linux kernel compilation $ make clean $ make mrproper $ make defconfig $ time make -j$(nproc) no real difference between runs.