From patchwork Fri Sep 20 19:50:37 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Leonardo Bras X-Patchwork-Id: 1165419 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 46ZkwC67vsz9s4Y for ; Sat, 21 Sep 2019 05:55:23 +1000 (AEST) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.ibm.com Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 46ZkwC4tcdzDqgd for ; Sat, 21 Sep 2019 05:55:23 +1000 (AEST) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: lists.ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=linux.ibm.com (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=leonardo@linux.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.ibm.com Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 46Zkqx33YWzF10g for ; Sat, 21 Sep 2019 05:51:41 +1000 (AEST) Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x8KJm141039068; Fri, 20 Sep 2019 15:51:22 -0400 Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 2v50uetuk4-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 20 Sep 2019 15:51:22 -0400 Received: from m0098396.ppops.net (m0098396.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.27/8.16.0.27) with SMTP id x8KJnH6A042230; Fri, 20 Sep 2019 15:51:22 -0400 Received: from ppma05wdc.us.ibm.com (1b.90.2fa9.ip4.static.sl-reverse.com [169.47.144.27]) by mx0a-001b2d01.pphosted.com with ESMTP id 2v50uetujg-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 20 Sep 2019 15:51:21 -0400 Received: from pps.filterd (ppma05wdc.us.ibm.com [127.0.0.1]) by ppma05wdc.us.ibm.com (8.16.0.27/8.16.0.27) with SMTP id x8KJoHqe015546; Fri, 20 Sep 2019 19:51:20 GMT Received: from b03cxnp08027.gho.boulder.ibm.com (b03cxnp08027.gho.boulder.ibm.com [9.17.130.19]) by ppma05wdc.us.ibm.com with ESMTP id 2v3vbu8p2f-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 20 Sep 2019 19:51:20 +0000 Received: from b03ledav004.gho.boulder.ibm.com (b03ledav004.gho.boulder.ibm.com [9.17.130.235]) by b03cxnp08027.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x8KJpJPZ54788488 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 20 Sep 2019 19:51:19 GMT Received: from b03ledav004.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2EE4278060; Fri, 20 Sep 2019 19:51:19 +0000 (GMT) Received: from b03ledav004.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 931697805E; Fri, 20 Sep 2019 19:51:14 +0000 (GMT) Received: from LeoBras.aus.stglabs.ibm.com (unknown [9.18.235.184]) by b03ledav004.gho.boulder.ibm.com (Postfix) with ESMTP; Fri, 20 Sep 2019 19:51:14 +0000 (GMT) From: Leonardo Bras To: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 01/11] powerpc/mm: Adds counting method to monitor lockless pgtable walks Date: Fri, 20 Sep 2019 16:50:37 -0300 Message-Id: <20190920195047.7703-2-leonardo@linux.ibm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190920195047.7703-1-leonardo@linux.ibm.com> References: <20190920195047.7703-1-leonardo@linux.ibm.com> MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-09-20_07:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1909200161 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: Keith Busch , Richard Fontana , Paul Mackerras , Ira Weiny , Dan Williams , "Aneesh Kumar K.V" , YueHaibing , Mike Rapoport , Jason Gunthorpe , Ganesh Goudar , Mahesh Salgaonkar , Leonardo Bras , Arnd Bergmann , John Hubbard , Nicholas Piggin , Thomas Gleixner , Allison Randal , Greg Kroah-Hartman , Andrew Morton Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" It's necessary to monitor lockless pagetable walks, in order to avoid doing THP splitting/collapsing during them. Some methods rely on local_irq_{save,restore}, but that can be slow on cases with a lot of cpus are used for the process. In order to speedup some cases, I propose a refcount-based approach, that counts the number of lockless pagetable walks happening on the process. This method does not exclude the current irq-oriented method. It works as a complement to skip unnecessary waiting. start_lockless_pgtbl_walk(mm) Insert before starting any lockless pgtable walk end_lockless_pgtbl_walk(mm) Insert after the end of any lockless pgtable walk (Mostly after the ptep is last used) running_lockless_pgtbl_walk(mm) Returns the number of lockless pgtable walks running Signed-off-by: Leonardo Bras --- arch/powerpc/include/asm/book3s/64/mmu.h | 3 +++ arch/powerpc/mm/book3s64/mmu_context.c | 1 + arch/powerpc/mm/book3s64/pgtable.c | 17 +++++++++++++++++ 3 files changed, 21 insertions(+) diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/include/asm/book3s/64/mmu.h index 23b83d3593e2..13b006e7dde4 100644 --- a/arch/powerpc/include/asm/book3s/64/mmu.h +++ b/arch/powerpc/include/asm/book3s/64/mmu.h @@ -116,6 +116,9 @@ typedef struct { /* Number of users of the external (Nest) MMU */ atomic_t copros; + /* Number of running instances of lockless pagetable walk*/ + atomic_t lockless_pgtbl_walk_count; + struct hash_mm_context *hash_context; unsigned long vdso_base; diff --git a/arch/powerpc/mm/book3s64/mmu_context.c b/arch/powerpc/mm/book3s64/mmu_context.c index 2d0cb5ba9a47..3dd01c0ca5be 100644 --- a/arch/powerpc/mm/book3s64/mmu_context.c +++ b/arch/powerpc/mm/book3s64/mmu_context.c @@ -200,6 +200,7 @@ int init_new_context(struct task_struct *tsk, struct mm_struct *mm) #endif atomic_set(&mm->context.active_cpus, 0); atomic_set(&mm->context.copros, 0); + atomic_set(&mm->context.lockless_pgtbl_walk_count, 0); return 0; } diff --git a/arch/powerpc/mm/book3s64/pgtable.c b/arch/powerpc/mm/book3s64/pgtable.c index 7d0e0d0d22c4..13239b17a22c 100644 --- a/arch/powerpc/mm/book3s64/pgtable.c +++ b/arch/powerpc/mm/book3s64/pgtable.c @@ -98,6 +98,23 @@ void serialize_against_pte_lookup(struct mm_struct *mm) smp_call_function_many(mm_cpumask(mm), do_nothing, NULL, 1); } +void start_lockless_pgtbl_walk(struct mm_struct *mm) +{ + atomic_inc(&mm->context.lockless_pgtbl_walk_count); +} +EXPORT_SYMBOL(start_lockless_pgtbl_walk); + +void end_lockless_pgtbl_walk(struct mm_struct *mm) +{ + atomic_dec(&mm->context.lockless_pgtbl_walk_count); +} +EXPORT_SYMBOL(end_lockless_pgtbl_walk); + +int running_lockless_pgtbl_walk(struct mm_struct *mm) +{ + return atomic_read(&mm->context.lockless_pgtbl_walk_count); +} + /* * We use this to invalidate a pmdp entry before switching from a * hugepte to regular pmd entry.