From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753570AbdHQWFi (ORCPT ); Thu, 17 Aug 2017 18:05:38 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:41111 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753147AbdHQWFh (ORCPT ); Thu, 17 Aug 2017 18:05:37 -0400 From: Laurent Dufour To: paulmck@linux.vnet.ibm.com, peterz@infradead.org, akpm@linux-foundation.org, kirill@shutemov.name, ak@linux.intel.com, mhocko@kernel.org, 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 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, Tim Chen , linuxppc-dev@lists.ozlabs.org, x86@kernel.org Subject: [PATCH v2 00/20] Speculative page faults Date: Fri, 18 Aug 2017 00:04:59 +0200 X-Mailer: git-send-email 2.7.4 X-TM-AS-GCONF: 00 x-cbid: 17081722-0008-0000-0000-0000048E7A7A X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17081722-0009-0000-0000-00001E1E7D72 Message-Id: <1503007519-26777-1-git-send-email-ldufour@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-08-17_12:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=2 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1707230000 definitions=main-1708170357 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is a port on kernel 4.13 of the work done by Peter Zijlstra to handle page fault without holding the mm semaphore [1]. The idea is to 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 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. The speculative page fault (SPF) has to look for the VMA matching the fault address without holding the mmap_sem, so the VMA list is now managed using SRCU allowing lockless walking. The only impact would be the deferred file derefencing in the case of a file mapping, since the file pointer is released once the SRCU cleaning is done. This patch relies on the change done recently by Paul McKenney in SRCU which now runs a callback per CPU instead of per SRCU structure [1]. The VMA's attributes checked during the speculative page fault processing have to be protected against parallel changes. This is done by using a per VMA sequence lock. This sequence lock allows the speculative page fault handler to fast check for parallel changes in progress and to abort the speculative page fault in that case. Once the VMA is found, the speculative page fault handler would check for the VMA's attributes to verify that the page fault has to be handled correctly or not. Thus the VMA is protected through a sequence lock which allows fast detection of concurrent VMA changes. If such a change is detected, the speculative page fault is aborted and a *classic* page fault is tried. VMA sequence locks are added when VMA attributes which are checked during the page fault are modified. When the PTE is fetched, the VMA is checked to see if it has been changed, so once the page table is locked, the VMA is valid, so any other changes leading to touching this PTE will need to lock the page table, so no parallel change is possible at this time. Compared to the Peter's initial work, this series introduces a spin_trylock when dealing with speculative page fault. This is required to avoid dead lock when handling a page fault while a TLB invalidate is requested by an other CPU holding the PTE. Another change due to a lock dependency issue with mapping->i_mmap_rwsem. In addition some VMA field values which are used once the PTE is unlocked at the end the page fault path are saved into the vm_fault structure to used the values matching the VMA at the time the PTE was locked. This series builds on top of v4.13-rc5 and is functional on x86 and PowerPC. Tests have been made using a large commercial in-memory database on a PowerPC system with 752 CPU using RFC v5. The results are very encouraging since the loading of the 2TB database was faster by 14% with the speculative page fault. Using ebizzy test [3], which spreads a lot of threads, the result are good when running on both a large or a small system. When using kernbench, the result are quite similar which expected as not so much multithreaded processes are involved. But there is no performance degradation neither which is good. ------------------ Benchmarks results Note these test have been made on top of 4.13-rc3 with the following patch from Paul McKenney applied: "srcu: Provide ordering for CPU not involved in grace period" [5] Ebizzy: ------- The test is counting the number of records per second it can manage, the higher is the best. I run it like this 'ebizzy -mTRp'. To get consistent result I repeated the test 100 times and measure the average result, mean deviation, max and min. - 16 CPUs x86 VM Records/s 4.13-rc5 4.13-rc5-spf Average 11350.29 21760.36 Mean deviation 396.56 881.40 Max 13773 26194 Min 10567 19223 - 80 CPUs Power 8 node: Records/s 4.13-rc5 4.13-rc5-spf Average 33904.67 58847.91 Mean deviation 789.40 1753.19 Max 36703 68958 Min 31759 55125 The number of record per second is far better with the speculative page fault. The mean deviation is higher with the speculative page fault, may be because sometime the fault are not handled in a speculative way leading to more variation. Kernbench: ---------- This test is building a 4.12 kernel using platform default config. The build has been run 5 times each time. - 16 CPUs x86 VM Average Half load -j 8 Run (std deviation) 4.13.0-rc5 4.13.0-rc5-spf Elapsed Time 166.574 (0.340779) 145.754 (0.776325) User Time 1080.77 (2.05871) 999.272 (4.12142) System Time 204.594 (1.02449) 116.362 (1.22974) Percent CPU 771.2 (1.30384) 765 (0.707107) Context Switches 46590.6 (935.591) 66316.4 (744.64) Sleeps 84421.2 (596.612) 85186 (523.041) Average Optimal load -j 16 Run (std deviation) 4.13.0-rc5 4.13.0-rc5-spf Elapsed Time 85.422 (0.42293) 74.81 (0.419345) User Time 1031.79 (51.6557) 954.912 (46.8439) System Time 186.528 (19.0575) 107.514 (9.36902) Percent CPU 1059.2 (303.607) 1056.8 (307.624) Context Switches 67240.3 (21788.9) 89360.6 (24299.9) Sleeps 89607.8 (5511.22) 90372.5 (5490.16) The elapsed time is a bit shorter in the case of the SPF release, but the impact less important since there are less multithreaded processes involved here. - 80 CPUs Power 8 node: Average Half load -j 40 Run (std deviation) 4.13.0-rc5 4.13.0-rc5-spf Elapsed Time 117.176 (0.824093) 116.792 (0.695392) User Time 4412.34 (24.29) 4396.02 (24.4819) System Time 131.106 (1.28343) 133.452 (0.708851) Percent CPU 3876.8 (18.1439) 3877.6 (21.9955) Context Switches 72470.2 (466.181) 72971 (673.624) Sleeps 161294 (2284.85) 161946 (2217.9) Average Optimal load -j 80 Run (std deviation) 4.13.0-rc5 4.13.0-rc5-spf Elapsed Time 111.176 (1.11123) 111.242 (0.801542) User Time 5930.03 (1600.07) 5929.89 (1617) System Time 166.258 (37.0662) 169.337 (37.8419) Percent CPU 5378.5 (1584.16) 5385.6 (1590.24) Context Switches 117389 (47350.1) 130132 (60256.3) Sleeps 163354 (4153.9) 163219 (2251.27) Here the elapsed time is a bit shorter using the spf release, but we remain in the error margin. It has to be noted that this system is not correctly balanced on the NUMA point of view as all the available memory is attached to one core. ------------------------ Changes since v1: - Remove PERF_COUNT_SW_SPF_FAILED perf event. - Add tracing events to details speculative page fault failures. - Cache VMA fields values which are used once the PTE is unlocked at the end of the page fault events. - Ensure that fields read during the speculative path are written and read using WRITE_ONCE and READ_ONCE. - Add checks at the beginning of the speculative path to abort it if the VMA is known to not be supported. Changes since RFC V5 [6] - Port to 4.13 kernel - Merging patch fixing lock dependency into the original patch - Replace the 2 parameters of vma_has_changed() with the vmf pointer - In patch 7, don't call __do_fault() in the speculative path as it may want to unlock the mmap_sem. - In patch 11-12, don't check for vma boundaries when page_add_new_anon_rmap() is called during the spf path and protect against anon_vma pointer's update. - In patch 13-16, add performance events to report number of successful and failed speculative events. [1] http://linux-kernel.2935.n7.nabble.com/RFC-PATCH-0-6-Another-go-at-speculative-page-faults-tt965642.html#none [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=da915ad5cf25b5f5d358dd3670c3378d8ae8c03e [3] http://ebizzy.sourceforge.net/ [4] http://ck.kolivas.org/apps/kernbench/kernbench-0.50/ [5] https://lkml.org/lkml/2017/7/24/829 [6] https://lwn.net/Articles/725607/ Laurent Dufour (14): mm: Introduce pte_spinlock for FAULT_FLAG_SPECULATIVE mm: Protect VMA modifications using VMA sequence count mm: Cache some VMA fields in the vm_fault structure mm: Protect SPF handler against anon_vma changes mm/migrate: Pass vm_fault pointer to migrate_misplaced_page() mm: Introduce __lru_cache_add_active_or_unevictable mm: Introduce __maybe_mkwrite() mm: Introduce __vm_normal_page() mm: Introduce __page_add_new_anon_rmap() mm: Try spin lock in speculative path mm: Adding speculative page fault failure trace events perf: Add a speculative page fault sw event perf tools: Add support for the SPF perf event powerpc/mm: Add speculative page fault Peter Zijlstra (6): mm: Dont assume page-table invariance during faults mm: Prepare for FAULT_FLAG_SPECULATIVE mm: VMA sequence count mm: RCU free VMAs mm: Provide speculative fault infrastructure x86/mm: Add speculative pagefault handling arch/powerpc/include/asm/book3s/64/pgtable.h | 5 + arch/powerpc/mm/fault.c | 30 +- arch/x86/include/asm/pgtable_types.h | 7 + arch/x86/mm/fault.c | 19 ++ fs/proc/task_mmu.c | 5 +- fs/userfaultfd.c | 17 +- include/linux/hugetlb_inline.h | 2 +- include/linux/migrate.h | 4 +- include/linux/mm.h | 21 +- include/linux/mm_types.h | 3 + include/linux/pagemap.h | 4 +- include/linux/rmap.h | 12 +- include/linux/swap.h | 11 +- include/trace/events/pagefault.h | 87 +++++ include/uapi/linux/perf_event.h | 1 + kernel/fork.c | 1 + mm/hugetlb.c | 2 + mm/init-mm.c | 1 + mm/internal.h | 19 ++ mm/khugepaged.c | 5 + mm/madvise.c | 6 +- mm/memory.c | 474 ++++++++++++++++++++++----- mm/mempolicy.c | 51 ++- mm/migrate.c | 4 +- mm/mlock.c | 13 +- mm/mmap.c | 138 ++++++-- mm/mprotect.c | 4 +- mm/mremap.c | 7 + mm/rmap.c | 5 +- mm/swap.c | 12 +- tools/include/uapi/linux/perf_event.h | 1 + tools/perf/util/evsel.c | 1 + tools/perf/util/parse-events.c | 4 + tools/perf/util/parse-events.l | 1 + tools/perf/util/python.c | 1 + 35 files changed, 803 insertions(+), 175 deletions(-) create mode 100644 include/trace/events/pagefault.h -- 2.7.4 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f200.google.com (mail-io0-f200.google.com [209.85.223.200]) by kanga.kvack.org (Postfix) with ESMTP id DD2CB6B025F for ; Thu, 17 Aug 2017 18:05:38 -0400 (EDT) Received: by mail-io0-f200.google.com with SMTP id p141so5975078iop.6 for ; Thu, 17 Aug 2017 15:05:38 -0700 (PDT) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com. 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Violators will be prosecuted for from ; Thu, 17 Aug 2017 23:05:33 +0100 From: Laurent Dufour Subject: [PATCH v2 00/20] Speculative page faults Date: Fri, 18 Aug 2017 00:04:59 +0200 Message-Id: <1503007519-26777-1-git-send-email-ldufour@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: paulmck@linux.vnet.ibm.com, peterz@infradead.org, akpm@linux-foundation.org, kirill@shutemov.name, ak@linux.intel.com, mhocko@kernel.org, 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 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, Tim Chen , linuxppc-dev@lists.ozlabs.org, x86@kernel.org This is a port on kernel 4.13 of the work done by Peter Zijlstra to handle page fault without holding the mm semaphore [1]. The idea is to 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 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. The speculative page fault (SPF) has to look for the VMA matching the fault address without holding the mmap_sem, so the VMA list is now managed using SRCU allowing lockless walking. The only impact would be the deferred file derefencing in the case of a file mapping, since the file pointer is released once the SRCU cleaning is done. This patch relies on the change done recently by Paul McKenney in SRCU which now runs a callback per CPU instead of per SRCU structure [1]. The VMA's attributes checked during the speculative page fault processing have to be protected against parallel changes. This is done by using a per VMA sequence lock. This sequence lock allows the speculative page fault handler to fast check for parallel changes in progress and to abort the speculative page fault in that case. Once the VMA is found, the speculative page fault handler would check for the VMA's attributes to verify that the page fault has to be handled correctly or not. Thus the VMA is protected through a sequence lock which allows fast detection of concurrent VMA changes. If such a change is detected, the speculative page fault is aborted and a *classic* page fault is tried. VMA sequence locks are added when VMA attributes which are checked during the page fault are modified. When the PTE is fetched, the VMA is checked to see if it has been changed, so once the page table is locked, the VMA is valid, so any other changes leading to touching this PTE will need to lock the page table, so no parallel change is possible at this time. Compared to the Peter's initial work, this series introduces a spin_trylock when dealing with speculative page fault. This is required to avoid dead lock when handling a page fault while a TLB invalidate is requested by an other CPU holding the PTE. Another change due to a lock dependency issue with mapping->i_mmap_rwsem. In addition some VMA field values which are used once the PTE is unlocked at the end the page fault path are saved into the vm_fault structure to used the values matching the VMA at the time the PTE was locked. This series builds on top of v4.13-rc5 and is functional on x86 and PowerPC. Tests have been made using a large commercial in-memory database on a PowerPC system with 752 CPU using RFC v5. The results are very encouraging since the loading of the 2TB database was faster by 14% with the speculative page fault. Using ebizzy test [3], which spreads a lot of threads, the result are good when running on both a large or a small system. When using kernbench, the result are quite similar which expected as not so much multithreaded processes are involved. But there is no performance degradation neither which is good. ------------------ Benchmarks results Note these test have been made on top of 4.13-rc3 with the following patch from Paul McKenney applied: "srcu: Provide ordering for CPU not involved in grace period" [5] Ebizzy: ------- The test is counting the number of records per second it can manage, the higher is the best. I run it like this 'ebizzy -mTRp'. To get consistent result I repeated the test 100 times and measure the average result, mean deviation, max and min. - 16 CPUs x86 VM Records/s 4.13-rc5 4.13-rc5-spf Average 11350.29 21760.36 Mean deviation 396.56 881.40 Max 13773 26194 Min 10567 19223 - 80 CPUs Power 8 node: Records/s 4.13-rc5 4.13-rc5-spf Average 33904.67 58847.91 Mean deviation 789.40 1753.19 Max 36703 68958 Min 31759 55125 The number of record per second is far better with the speculative page fault. The mean deviation is higher with the speculative page fault, may be because sometime the fault are not handled in a speculative way leading to more variation. Kernbench: ---------- This test is building a 4.12 kernel using platform default config. The build has been run 5 times each time. - 16 CPUs x86 VM Average Half load -j 8 Run (std deviation) 4.13.0-rc5 4.13.0-rc5-spf Elapsed Time 166.574 (0.340779) 145.754 (0.776325) User Time 1080.77 (2.05871) 999.272 (4.12142) System Time 204.594 (1.02449) 116.362 (1.22974) Percent CPU 771.2 (1.30384) 765 (0.707107) Context Switches 46590.6 (935.591) 66316.4 (744.64) Sleeps 84421.2 (596.612) 85186 (523.041) Average Optimal load -j 16 Run (std deviation) 4.13.0-rc5 4.13.0-rc5-spf Elapsed Time 85.422 (0.42293) 74.81 (0.419345) User Time 1031.79 (51.6557) 954.912 (46.8439) System Time 186.528 (19.0575) 107.514 (9.36902) Percent CPU 1059.2 (303.607) 1056.8 (307.624) Context Switches 67240.3 (21788.9) 89360.6 (24299.9) Sleeps 89607.8 (5511.22) 90372.5 (5490.16) The elapsed time is a bit shorter in the case of the SPF release, but the impact less important since there are less multithreaded processes involved here. - 80 CPUs Power 8 node: Average Half load -j 40 Run (std deviation) 4.13.0-rc5 4.13.0-rc5-spf Elapsed Time 117.176 (0.824093) 116.792 (0.695392) User Time 4412.34 (24.29) 4396.02 (24.4819) System Time 131.106 (1.28343) 133.452 (0.708851) Percent CPU 3876.8 (18.1439) 3877.6 (21.9955) Context Switches 72470.2 (466.181) 72971 (673.624) Sleeps 161294 (2284.85) 161946 (2217.9) Average Optimal load -j 80 Run (std deviation) 4.13.0-rc5 4.13.0-rc5-spf Elapsed Time 111.176 (1.11123) 111.242 (0.801542) User Time 5930.03 (1600.07) 5929.89 (1617) System Time 166.258 (37.0662) 169.337 (37.8419) Percent CPU 5378.5 (1584.16) 5385.6 (1590.24) Context Switches 117389 (47350.1) 130132 (60256.3) Sleeps 163354 (4153.9) 163219 (2251.27) Here the elapsed time is a bit shorter using the spf release, but we remain in the error margin. It has to be noted that this system is not correctly balanced on the NUMA point of view as all the available memory is attached to one core. ------------------------ Changes since v1: - Remove PERF_COUNT_SW_SPF_FAILED perf event. - Add tracing events to details speculative page fault failures. - Cache VMA fields values which are used once the PTE is unlocked at the end of the page fault events. - Ensure that fields read during the speculative path are written and read using WRITE_ONCE and READ_ONCE. - Add checks at the beginning of the speculative path to abort it if the VMA is known to not be supported. Changes since RFC V5 [6] - Port to 4.13 kernel - Merging patch fixing lock dependency into the original patch - Replace the 2 parameters of vma_has_changed() with the vmf pointer - In patch 7, don't call __do_fault() in the speculative path as it may want to unlock the mmap_sem. - In patch 11-12, don't check for vma boundaries when page_add_new_anon_rmap() is called during the spf path and protect against anon_vma pointer's update. - In patch 13-16, add performance events to report number of successful and failed speculative events. [1] http://linux-kernel.2935.n7.nabble.com/RFC-PATCH-0-6-Another-go-at-speculative-page-faults-tt965642.html#none [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=da915ad5cf25b5f5d358dd3670c3378d8ae8c03e [3] http://ebizzy.sourceforge.net/ [4] http://ck.kolivas.org/apps/kernbench/kernbench-0.50/ [5] https://lkml.org/lkml/2017/7/24/829 [6] https://lwn.net/Articles/725607/ Laurent Dufour (14): mm: Introduce pte_spinlock for FAULT_FLAG_SPECULATIVE mm: Protect VMA modifications using VMA sequence count mm: Cache some VMA fields in the vm_fault structure mm: Protect SPF handler against anon_vma changes mm/migrate: Pass vm_fault pointer to migrate_misplaced_page() mm: Introduce __lru_cache_add_active_or_unevictable mm: Introduce __maybe_mkwrite() mm: Introduce __vm_normal_page() mm: Introduce __page_add_new_anon_rmap() mm: Try spin lock in speculative path mm: Adding speculative page fault failure trace events perf: Add a speculative page fault sw event perf tools: Add support for the SPF perf event powerpc/mm: Add speculative page fault Peter Zijlstra (6): mm: Dont assume page-table invariance during faults mm: Prepare for FAULT_FLAG_SPECULATIVE mm: VMA sequence count mm: RCU free VMAs mm: Provide speculative fault infrastructure x86/mm: Add speculative pagefault handling arch/powerpc/include/asm/book3s/64/pgtable.h | 5 + arch/powerpc/mm/fault.c | 30 +- arch/x86/include/asm/pgtable_types.h | 7 + arch/x86/mm/fault.c | 19 ++ fs/proc/task_mmu.c | 5 +- fs/userfaultfd.c | 17 +- include/linux/hugetlb_inline.h | 2 +- include/linux/migrate.h | 4 +- include/linux/mm.h | 21 +- include/linux/mm_types.h | 3 + include/linux/pagemap.h | 4 +- include/linux/rmap.h | 12 +- include/linux/swap.h | 11 +- include/trace/events/pagefault.h | 87 +++++ include/uapi/linux/perf_event.h | 1 + kernel/fork.c | 1 + mm/hugetlb.c | 2 + mm/init-mm.c | 1 + mm/internal.h | 19 ++ mm/khugepaged.c | 5 + mm/madvise.c | 6 +- mm/memory.c | 474 ++++++++++++++++++++++----- mm/mempolicy.c | 51 ++- mm/migrate.c | 4 +- mm/mlock.c | 13 +- mm/mmap.c | 138 ++++++-- mm/mprotect.c | 4 +- mm/mremap.c | 7 + mm/rmap.c | 5 +- mm/swap.c | 12 +- tools/include/uapi/linux/perf_event.h | 1 + tools/perf/util/evsel.c | 1 + tools/perf/util/parse-events.c | 4 + tools/perf/util/parse-events.l | 1 + tools/perf/util/python.c | 1 + 35 files changed, 803 insertions(+), 175 deletions(-) create mode 100644 include/trace/events/pagefault.h -- 2.7.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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