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Mon, 30 May 2022 09:20:54 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7A464A4054; Mon, 30 May 2022 09:35:14 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 55577A405B; Mon, 30 May 2022 09:35:11 +0000 (GMT) Received: from [9.171.2.176] (unknown [9.171.2.176]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 30 May 2022 09:35:11 +0000 (GMT) Message-ID: <33fd4731-9765-d78b-bdc3-f8243c98e81f@linux.ibm.com> Date: Mon, 30 May 2022 11:35:10 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [PATCH v4] mm: Avoid unnecessary page fault retires on shared memory types Content-Language: en-US To: Heiko Carstens , Peter Xu References: <20220527193936.30678-1-peterx@redhat.com> From: Christian Borntraeger In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 17H2zOn_Mc5hu2MUIDRxY-AXp5vXE9mJ X-Proofpoint-ORIG-GUID: M8apowNso6iR-DwO9jx-r0DSHd-NwVxB X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.874,Hydra:6.0.486,FMLib:17.11.64.514 definitions=2022-05-30_03,2022-05-27_01,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 suspectscore=0 adultscore=0 mlxscore=0 bulkscore=0 malwarescore=0 spamscore=0 clxscore=1011 mlxlogscore=980 lowpriorityscore=0 phishscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2204290000 definitions=main-2205300050 X-Mailman-Approved-At: Tue, 31 May 2022 08:25:41 +1000 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Rich Felker , linux-ia64@vger.kernel.org, David Hildenbrand , Peter Zijlstra , Dave Hansen , x86@kernel.org, linux-mips@vger.kernel.org, "James E . J . Bottomley" , linux-mm@kvack.org, Guo Ren , "H . Peter Anvin" , sparclinux@vger.kernel.org, linux-hexagon@vger.kernel.org, Alexander Gordeev , Will Deacon , Thomas Gleixner , Paul Mackerras , Anton Ivanov , Jonas Bonn , linux-s390@vger.kernel.org, Janosch Frank , Yoshinori Sato , linux-sh@vger.kernel.org, Helge Deller , Alistair Popple , Hugh Dickins , Russell King , linux-csky@vger.kernel.org, Ingo Molnar , Andrea Arcangeli , Geert Uytterhoeven , linux-arm-kernel@lists.infradead.org, Vineet Gupta , Matt Turner , linux-snps-arc@lists.infradead.org, Catalin Marinas , linux-xtensa@linux-xtensa.org, Albert Ou , Vasily Gorbik , Chris Zankel , Johannes Weiner , linux-um@lists.infradead.org, Nicholas Piggin , Stefan Kristiansson , Richard Weinberger , linux-m68k@lists.linux-m68k.org, openrisc@lists.librecores.org, Borislav Petkov , Al Viro , Andy Lutomirski , Paul Walmsley , Stafford Horne , Ingo Molnar , Vlastimil Babka , Richard Henderson , Brian Cain , Michal Simek , Thomas Bogendoerfer , linux-parisc@vger.kernel.org, Max Filippov , linux-kernel@vger.kernel.org, Johannes Berg , Dinh Nguyen , linux-riscv@lists.infradead.org, Palmer Dabbelt , Sven Schnelle , linux-alpha@vger.kernel.org, Ivan Kokshaysky , Andrew Morton , linuxppc-dev@lists.ozlabs.org, "David S . Miller" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Am 29.05.22 um 22:33 schrieb Heiko Carstens: [...] > > Guess the patch below on top of your patch is what we want. > Just for clarification: if gmap is not NULL then the process is a kvm > process. So, depending on the workload, this optimization makes sense. > > diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c > index 4608cc962ecf..e1d40ca341b7 100644 > --- a/arch/s390/mm/fault.c > +++ b/arch/s390/mm/fault.c > @@ -436,12 +436,11 @@ static inline vm_fault_t do_exception(struct pt_regs *regs, int access) > > /* The fault is fully completed (including releasing mmap lock) */ > if (fault & VM_FAULT_COMPLETED) { > - /* > - * Gmap will need the mmap lock again, so retake it. TODO: > - * only conditionally take the lock when CONFIG_PGSTE set. > - */ > - mmap_read_lock(mm); > - goto out_gmap; > + if (gmap) { > + mmap_read_lock(mm); > + goto out_gmap; > + } > + goto out; Yes, that makes sense. With that Acked-by: Christian Borntraeger