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Tue, 26 Nov 2024 12:11:46 +0000 (GMT) Date: Tue, 26 Nov 2024 13:11:44 +0100 From: Claudio Imbrenda To: Heiko Carstens Cc: Christian Borntraeger , Janosch Frank , David Hildenbrand , kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 0/3] KVM: s390: Couple of small cmpxchg() optimizations Message-ID: <20241126131144.0a076101@p-imbrenda> In-Reply-To: <20241126102515.3178914-1-hca@linux.ibm.com> References: <20241126102515.3178914-1-hca@linux.ibm.com> Organization: IBM X-Mailer: Claws Mail 4.3.0 (GTK 3.24.43; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: IZ6z6AJwRAl1qDa--NiJF6Vnq671tAeO X-Proofpoint-ORIG-GUID: IZ6z6AJwRAl1qDa--NiJF6Vnq671tAeO X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 priorityscore=1501 lowpriorityscore=0 mlxlogscore=767 bulkscore=0 spamscore=0 impostorscore=0 mlxscore=0 suspectscore=0 malwarescore=0 adultscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2409260000 definitions=main-2411260097 On Tue, 26 Nov 2024 11:25:12 +0100 Heiko Carstens wrote: looks good, and it's a follow-up of your cmpxchg series, so I think it should go through the s390 kernel tree (but please try to add the comment in patch 3) > v2: > - Replace broken WRITE_ONCE(..., 9) with intended WRITE_ONCE(..., 0). > > v1: > Use try_cmpxchg() instead of cmpxchg() so compilers with flag output > operand support (gcc 14 and newer) can generate slightly better code. > > Also get rid of two cmpxchg() usages on one/two byte memory areas > which generates inefficient code. > > bloat-o-meter statistics of the kvm module: > > add/remove: 0/0 grow/shrink: 0/11 up/down: 0/-318 (-318) > Function old new delta > kvm_s390_handle_wait 886 880 -6 > kvm_s390_gisa_destroy 226 220 -6 > kvm_s390_gisa_clear 96 90 -6 > ipte_unlock 380 372 -8 > kvm_s390_gisc_unregister 270 260 -10 > kvm_s390_gisc_register 290 280 -10 > gisa_vcpu_kicker 200 190 -10 > account_mem 250 232 -18 > ipte_lock 416 368 -48 > kvm_s390_update_topology_change_report 174 122 -52 > kvm_s390_clear_local_irqs 420 276 -144 > Total: Before=316521, After=316203, chg -0.10% > > Heiko Carstens (3): > KVM: s390: Use try_cmpxchg() instead of cmpxchg() loops > KVM: s390: Remove one byte cmpxchg() usage > KVM: s390: Increase size of union sca_utility to four bytes > > arch/s390/include/asm/kvm_host.h | 10 +++++----- > arch/s390/kvm/gaccess.c | 16 ++++++++-------- > arch/s390/kvm/interrupt.c | 25 ++++++++----------------- > arch/s390/kvm/kvm-s390.c | 4 ++-- > arch/s390/kvm/pci.c | 5 ++--- > 5 files changed, 25 insertions(+), 35 deletions(-) >