From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752876AbeDQOsC (ORCPT ); Tue, 17 Apr 2018 10:48:02 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:38868 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753321AbeDQOd7 (ORCPT ); Tue, 17 Apr 2018 10:33:59 -0400 From: Laurent Dufour To: akpm@linux-foundation.org, mhocko@kernel.org, peterz@infradead.org, kirill@shutemov.name, ak@linux.intel.com, dave@stgolabs.net, jack@suse.cz, Matthew Wilcox , benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org, Thomas Gleixner , Ingo Molnar , hpa@zytor.com, Will Deacon , Sergey Senozhatsky , Andrea Arcangeli , Alexei Starovoitov , kemi.wang@intel.com, sergey.senozhatsky.work@gmail.com, Daniel Jordan , David Rientjes , Jerome Glisse , Ganesh Mahendran Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, haren@linux.vnet.ibm.com, khandual@linux.vnet.ibm.com, npiggin@gmail.com, bsingharora@gmail.com, paulmck@linux.vnet.ibm.com, Tim Chen , linuxppc-dev@lists.ozlabs.org, x86@kernel.org Subject: [PATCH v10 01/25] mm: introduce CONFIG_SPECULATIVE_PAGE_FAULT Date: Tue, 17 Apr 2018 16:33:07 +0200 X-Mailer: git-send-email 2.7.4 In-Reply-To: <1523975611-15978-1-git-send-email-ldufour@linux.vnet.ibm.com> References: <1523975611-15978-1-git-send-email-ldufour@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18041714-0012-0000-0000-000005CBDCCC X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18041714-0013-0000-0000-000019482804 Message-Id: <1523975611-15978-2-git-send-email-ldufour@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-04-17_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 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1804170131 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This configuration variable will be used to build the code needed to handle speculative page fault. By default it is turned off, and activated depending on architecture support, SMP and MMU. Suggested-by: Thomas Gleixner Suggested-by: David Rientjes Signed-off-by: Laurent Dufour --- mm/Kconfig | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/mm/Kconfig b/mm/Kconfig index d5004d82a1d6..5484dca11199 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -752,3 +752,25 @@ config GUP_BENCHMARK performance of get_user_pages_fast(). See tools/testing/selftests/vm/gup_benchmark.c + +config ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT + def_bool n + +config SPECULATIVE_PAGE_FAULT + bool "Speculative page faults" + default y + depends on ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT + depends on MMU && SMP + help + Try to handle user space page faults without holding the mmap_sem. + + This should allow better concurrency for massively threaded process + since the page fault handler will not wait for other threads memory + layout change to be done, assuming that this change is done in another + part of the process's memory space. This type of page fault is named + speculative page fault. + + If the speculative page fault fails because of a concurrency is + detected or because underlying PMD or PTE tables are not yet + allocating, it is failing its processing and a classic page fault + is then tried. -- 2.7.4