From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0687FC433FE for ; Mon, 30 May 2022 18:29:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 77F3B6B0072; Mon, 30 May 2022 14:29:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 72B826B0073; Mon, 30 May 2022 14:29:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5CA156B0074; Mon, 30 May 2022 14:29:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 4D83A6B0072 for ; Mon, 30 May 2022 14:29:45 -0400 (EDT) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 30BCF3502B for ; Mon, 30 May 2022 18:29:45 +0000 (UTC) X-FDA: 79523247930.10.1DB3136 Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) by imf06.hostedemail.com (Postfix) with ESMTP id E0936180048 for ; Mon, 30 May 2022 18:29:40 +0000 (UTC) Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 24UIM0H1024517; Mon, 30 May 2022 18:29:41 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=message-id : date : mime-version : subject : to : cc : references : from : in-reply-to : content-type : content-transfer-encoding; s=pp1; bh=J3XEFiqlO85yR0rlrt+0Ucb3kcbo/uXfSzDk57v+UvI=; b=sK08a5JRQZv/pRZYSijJfgzCNWcnImFCMS1209YIqfs77/e2+DqGCKxKlBXdJgBmlco8 lBUxmyGoc+OLGeLWYBYYR26O3FsvegFajhqOddNqC68LJDao5jNt43AilvT83QFtIU09 ymysBZ+7yYvC1vU7jJWa8h114YLyiWf0mvxibmh4UXnXn2YZzAzo8CIdHOnqkmFzsY1r B+BMFqTlkhhhT5CMeGiBcg1sFURj8WmM61cUPcqTMXIorBEaBI5LTzeO9gIr7HvJfINf FIjGzFOAKcrEWvMA8wWWcaPvQrckVA5zWZJHRK+ah1+o9L5zMidx1M1UKYE9RYi3B87E oA== Received: from pps.reinject (localhost [127.0.0.1]) by mx0b-001b2d01.pphosted.com (PPS) with ESMTPS id 3gd34y82yk-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 30 May 2022 18:29:40 +0000 Received: from m0098414.ppops.net (m0098414.ppops.net [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 24UIQonu010446; Mon, 30 May 2022 18:29:39 GMT Received: from ppma06fra.de.ibm.com (48.49.7a9f.ip4.static.sl-reverse.com [159.122.73.72]) by mx0b-001b2d01.pphosted.com (PPS) with ESMTPS id 3gd34y82y9-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 30 May 2022 18:29:39 +0000 Received: from pps.filterd (ppma06fra.de.ibm.com [127.0.0.1]) by ppma06fra.de.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 24UIM2B8011304; Mon, 30 May 2022 18:29:37 GMT Received: from b06cxnps4074.portsmouth.uk.ibm.com (d06relay11.portsmouth.uk.ibm.com [9.149.109.196]) by ppma06fra.de.ibm.com with ESMTP id 3gbcb7j9t2-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 30 May 2022 18:29:37 +0000 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 24UITYUm39059828 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 30 May 2022 18:29:34 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 12CBA5204F; Mon, 30 May 2022 18:29:34 +0000 (GMT) Received: from [9.171.42.121] (unknown [9.171.42.121]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id D9F875204E; Mon, 30 May 2022 18:29:30 +0000 (GMT) Message-ID: <58b163b1-22ec-7634-dcd3-5a0a54adec45@linux.ibm.com> Date: Mon, 30 May 2022 20:29:30 +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: Peter Xu Cc: Heiko Carstens , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Will Deacon , Matt Turner , linux-s390@vger.kernel.org, Andrew Morton , Brian Cain , Borislav Petkov , linux-alpha@vger.kernel.org, Alistair Popple , Jonas Bonn , linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, Michael Ellerman , Stefan Kristiansson , linux-snps-arc@lists.infradead.org, Vineet Gupta , Vasily Gorbik , Vlastimil Babka , Ivan Kokshaysky , Rich Felker , sparclinux@vger.kernel.org, Russell King , David Hildenbrand , Benjamin Herrenschmidt , Nicholas Piggin , "James E . J . Bottomley" , linux-xtensa@linux-xtensa.org, linux-sh@vger.kernel.org, Paul Walmsley , linux-m68k@lists.linux-m68k.org, linuxppc-dev@lists.ozlabs.org, Richard Henderson , Guo Ren , linux-parisc@vger.kernel.org, Andrea Arcangeli , Helge Deller , Al Viro , Albert Ou , linux-um@lists.infradead.org, "H . Peter Anvin" , Janosch Frank , Sven Schnelle , Anton Ivanov , openrisc@lists.librecores.org, Thomas Bogendoerfer , linux-hexagon@vger.kernel.org, Andy Lutomirski , Stafford Horne , linux-csky@vger.kernel.org, Thomas Gleixner , linux-mips@vger.kernel.org, Paul Mackerras , Alexander Gordeev , Dinh Nguyen , Palmer Dabbelt , "David S . Miller" , Johannes Weiner , Hugh Dickins , Ingo Molnar , Peter Zijlstra , linux-riscv@lists.infradead.org, Max Filippov , Catalin Marinas , Geert Uytterhoeven , Johannes Berg , Chris Zankel , Michal Simek , x86@kernel.org, Yoshinori Sato , Dave Hansen , Richard Weinberger , Ingo Molnar References: <20220527193936.30678-1-peterx@redhat.com> <33fd4731-9765-d78b-bdc3-f8243c98e81f@linux.ibm.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: BcnqcIajExbqAnGujS-ZUqcYMX48oxDt X-Proofpoint-ORIG-GUID: iK5fU7K0gq48iA5OulnJebFyFFDVydua X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.874,Hydra:6.0.517,FMLib:17.11.64.514 definitions=2022-05-30_07,2022-05-30_03,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 mlxscore=0 lowpriorityscore=0 priorityscore=1501 phishscore=0 suspectscore=0 adultscore=0 malwarescore=0 impostorscore=0 spamscore=0 mlxlogscore=999 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2204290000 definitions=main-2205300096 X-Rspamd-Queue-Id: E0936180048 X-Rspam-User: Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b=sK08a5JR; spf=pass (imf06.hostedemail.com: domain of borntraeger@linux.ibm.com designates 148.163.158.5 as permitted sender) smtp.mailfrom=borntraeger@linux.ibm.com; dmarc=pass (policy=none) header.from=ibm.com X-Stat-Signature: 7oat171q5hhg6h8bbedyfsmc1rgh7xkp X-Rspamd-Server: rspam05 X-HE-Tag: 1653935380-68760 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Am 30.05.22 um 18:00 schrieb Peter Xu: > On Mon, May 30, 2022 at 11:52:54AM -0400, Peter Xu wrote: >> On Mon, May 30, 2022 at 11:35:10AM +0200, Christian Borntraeger wrote: >>> >>> >>> 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; > > Hmm, right after I replied I found "goto out" could be problematic, since > all s390 callers of do_exception() will assume it an error condition (side > note: "goto out_gmap" contains one step to clear "fault" to 0). I'll > replace this with "return 0" instead if it looks good to both of you. > > I'll wait for a confirmation before reposting. Thanks, Yes, that sounds good and thank you for double checking.