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Tue, 2 Jun 2026 11:33:30 +0000 (GMT) Date: Tue, 2 Jun 2026 13:33:29 +0200 From: Alexander Gordeev To: Heiko Carstens Cc: Sven Schnelle , Vasily Gorbik , Christian Borntraeger , Juergen Christ , linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org Subject: Re: [PATCH v5 3/7] s390/percpu: Use new percpu code section for arch_this_cpu_add() Message-ID: <796d70eb-05ba-460f-931a-8e125a441a27-agordeev@linux.ibm.com> References: <20260526055702.1429061-1-hca@linux.ibm.com> <20260526055702.1429061-4-hca@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260526055702.1429061-4-hca@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjAyMDEwNiBTYWx0ZWRfX1c6pR1J7JV48 4MWDCZz13PdEqb3MukR7NgYfJ5me18p7t1WoqMkE3NHBtvWZvLx5x74KPHviN3+cXHrjbT8dl+0 x91aZUyMK8LdmDHvql0nS7c3Z/q6vq7bKx01iSQ4lTYFyQDdhuryhZojwpCKadFlOPZhnaRhdlj HnU5L+ScbnNfmwX1cGcJVahfQAgsr/98mlZIzvI9ji8Dj9ix6h/crWPW0vVBDusnjhBZRMLRafd nEJsYZDAxWGEHNFunkNESkVfkTc8yG6TQoXAWtT6PLVg3WlehoesyA7EJNA8IHcvUrLX6bYUIbS wR1XRRjE1yC4QWhhyosD3xl1Xm4j+5rKPmNRfggAqN7op9yWwr8ipGpEGpMoAfTEESybJ2A/p8r Cb34iIaOyjCfXd3z770OARlD5EN+6HV69WN1udcFJptqRZDOGTEm4F7w6c+AGZ/dsFQPFYYzrJq V47c/41VAvtdDboo+mQ== X-Proofpoint-ORIG-GUID: -js6YQ3SpbD3CnAQoMjgKycYUX6euwDd X-Authority-Analysis: v=2.4 cv=cOzQdFeN c=1 sm=1 tr=0 ts=6a1ebf8f cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=kj9zAlcOel0A:10 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VnNF1IyMAAAA:8 a=EnoTB24x4siXizMxxzYA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-GUID: -js6YQ3SpbD3CnAQoMjgKycYUX6euwDd X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-02_01,2026-05-28_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 impostorscore=0 lowpriorityscore=0 spamscore=0 bulkscore=0 malwarescore=0 phishscore=0 suspectscore=0 priorityscore=1501 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606020106 On Tue, May 26, 2026 at 07:56:58AM +0200, Heiko Carstens wrote: > Convert arch_this_cpu_add() to make use of the new percpu code section > infrastructure. > > With this the text size of the kernel image is reduced by ~76kb > (defconfig). Also more than 5300 generated preempt_schedule_notrace() > function calls within the kernel image (modules not counted) are removed. > > With: > > DEFINE_PER_CPU(long, foo); > void bar(long a) { this_cpu_add(foo, a); } > > Old arch_this_cpu_add() looks like this: > > 00000000000000c0 : > c0: c0 04 00 00 00 00 jgnop c0 > c6: eb 01 03 a8 00 6a asi 936,1 > cc: c4 18 00 00 00 00 lgrl %r1,cc > ce: R_390_GOTENT foo+0x2 > d2: e3 10 03 b8 00 08 ag %r1,952 > d8: eb 22 10 00 00 e8 laag %r2,%r2,0(%r1) > de: eb ff 03 a8 00 6e alsi 936,-1 > e4: a7 a4 00 05 jhe ee > e8: c0 f4 00 00 00 00 jg e8 > ea: R_390_PC32DBL __s390_indirect_jump_r14+0x2 > ee: c0 f4 00 00 00 00 jg ee > f0: R_390_PLT32DBL preempt_schedule_notrace+0x2 > > New arch_this_cpu_add() looks like this: > > 00000000000000c0 : > c0: c0 04 00 00 00 00 jgnop c0 > c6: c4 38 00 00 00 00 lgrl %r3,c6 > c8: R_390_GOTENT foo+0x2 > cc: b9 04 00 43 lgr %r4,%r3 > d0: eb 00 43 c0 00 52 mviy 960(%r0),4 > d6: e3 40 03 b8 00 08 ag %r4,952 > dc: eb 52 40 00 00 e8 laag %r5,%r2,0(%r4) > e2: eb 00 03 c0 00 52 mviy 960,0 > e8: c0 f4 00 00 00 00 jg e8 > ea: R_390_PC32DBL __s390_indirect_jump_r14+0x2 > > Note that the conditional function call is removed. > > Signed-off-by: Heiko Carstens > --- > arch/s390/include/asm/percpu.h | 65 ++++++++++++++++++++++------------ > 1 file changed, 43 insertions(+), 22 deletions(-) Acked-by: Alexander Gordeev