[PATCH v11 00/26] Speculative page faults

Song, HaiyanX haiyanx.song at intel.com
Fri Jul 13 13:56:17 AEST 2018


Hi Laurent,

I attached the perf-profile.gz file for case page_fault2 and page_fault3. These files were captured during test the related test case. 
Please help to check on these data if it can help you to find the higher change. Thanks.

File name perf-profile_page_fault2_head_THP-Always.gz, means the perf-profile result get from page_fault2 
    tested for head commit (a7a8993bfe3ccb54ad468b9f1799649e4ad1ff12) with THP_always configuration.

Best regards,
Haiyan Song

________________________________________
From: owner-linux-mm at kvack.org [owner-linux-mm at kvack.org] on behalf of Laurent Dufour [ldufour at linux.vnet.ibm.com]
Sent: Thursday, July 12, 2018 1:05 AM
To: Song, HaiyanX
Cc: akpm at linux-foundation.org; mhocko at kernel.org; peterz at infradead.org; kirill at shutemov.name; ak at linux.intel.com; dave at stgolabs.net; jack at suse.cz; Matthew Wilcox; khandual at linux.vnet.ibm.com; aneesh.kumar at linux.vnet.ibm.com; benh at kernel.crashing.org; mpe at ellerman.id.au; paulus at samba.org; Thomas Gleixner; Ingo Molnar; hpa at zytor.com; Will Deacon; Sergey Senozhatsky; sergey.senozhatsky.work at gmail.com; Andrea Arcangeli; Alexei Starovoitov; Wang, Kemi; Daniel Jordan; David Rientjes; Jerome Glisse; Ganesh Mahendran; Minchan Kim; Punit Agrawal; vinayak menon; Yang Shi; linux-kernel at vger.kernel.org; linux-mm at kvack.org; haren at linux.vnet.ibm.com; npiggin at gmail.com; bsingharora at gmail.com; paulmck at linux.vnet.ibm.com; Tim Chen; linuxppc-dev at lists.ozlabs.org; x86 at kernel.org
Subject: Re: [PATCH v11 00/26] Speculative page faults

Hi Haiyan,

Do you get a chance to capture some performance cycles on your system ?
I still can't get these numbers on my hardware.

Thanks,
Laurent.

On 04/07/2018 09:51, Laurent Dufour wrote:
> On 04/07/2018 05:23, Song, HaiyanX wrote:
>> Hi Laurent,
>>
>>
>> For the test result on Intel 4s skylake platform (192 CPUs, 768G Memory), the below test cases all were run 3 times.
>> I check the test results, only page_fault3_thread/enable THP have 6% stddev for head commit, other tests have lower stddev.
>
> Repeating the test only 3 times seems a bit too low to me.
>
> I'll focus on the higher change for the moment, but I don't have access to such
> a hardware.
>
> Is possible to provide a diff between base and SPF of the performance cycles
> measured when running page_fault3 and page_fault2 when the 20% change is detected.
>
> Please stay focus on the test case process to see exactly where the series is
> impacting.
>
> Thanks,
> Laurent.
>
>>
>> And I did not find other high variation on test case result.
>>
>> a). Enable THP
>> testcase                          base     stddev       change      head     stddev         metric
>> page_fault3/enable THP           10519      ± 3%        -20.5%      8368      ±6%          will-it-scale.per_thread_ops
>> page_fault2/enalbe THP            8281      ± 2%        -18.8%      6728                   will-it-scale.per_thread_ops
>> brk1/eanble THP                 998475                   -2.2%    976893                   will-it-scale.per_process_ops
>> context_switch1/enable THP      223910                   -1.3%    220930                   will-it-scale.per_process_ops
>> context_switch1/enable THP      233722                   -1.0%    231288                   will-it-scale.per_thread_ops
>>
>> b). Disable THP
>> page_fault3/disable THP          10856                  -23.1%      8344                   will-it-scale.per_thread_ops
>> page_fault2/disable THP           8147                  -18.8%      6613                   will-it-scale.per_thread_ops
>> brk1/disable THP                   957                    -7.9%      881                   will-it-scale.per_thread_ops
>> context_switch1/disable THP     237006                    -2.2%    231907                  will-it-scale.per_thread_ops
>> brk1/disable THP                997317                    -2.0%    977778                  will-it-scale.per_process_ops
>> page_fault3/disable THP         467454                    -1.8%    459251                  will-it-scale.per_process_ops
>> context_switch1/disable THP     224431                    -1.3%    221567                  will-it-scale.per_process_ops
>>
>>
>> Best regards,
>> Haiyan Song
>> ________________________________________
>> From: Laurent Dufour [ldufour at linux.vnet.ibm.com]
>> Sent: Monday, July 02, 2018 4:59 PM
>> To: Song, HaiyanX
>> Cc: akpm at linux-foundation.org; mhocko at kernel.org; peterz at infradead.org; kirill at shutemov.name; ak at linux.intel.com; dave at stgolabs.net; jack at suse.cz; Matthew Wilcox; khandual at linux.vnet.ibm.com; aneesh.kumar at linux.vnet.ibm.com; benh at kernel.crashing.org; mpe at ellerman.id.au; paulus at samba.org; Thomas Gleixner; Ingo Molnar; hpa at zytor.com; Will Deacon; Sergey Senozhatsky; sergey.senozhatsky.work at gmail.com; Andrea Arcangeli; Alexei Starovoitov; Wang, Kemi; Daniel Jordan; David Rientjes; Jerome Glisse; Ganesh Mahendran; Minchan Kim; Punit Agrawal; vinayak menon; Yang Shi; linux-kernel at vger.kernel.org; linux-mm at kvack.org; haren at linux.vnet.ibm.com; npiggin at gmail.com; bsingharora at gmail.com; paulmck at linux.vnet.ibm.com; Tim Chen; linuxppc-dev at lists.ozlabs.org; x86 at kernel.org
>> Subject: Re: [PATCH v11 00/26] Speculative page faults
>>
>> On 11/06/2018 09:49, Song, HaiyanX wrote:
>>> Hi Laurent,
>>>
>>> Regression test for v11 patch serials have been run, some regression is found by LKP-tools (linux kernel performance)
>>> tested on Intel 4s skylake platform. This time only test the cases which have been run and found regressions on
>>> V9 patch serials.
>>>
>>> The regression result is sorted by the metric will-it-scale.per_thread_ops.
>>> branch: Laurent-Dufour/Speculative-page-faults/20180520-045126
>>> commit id:
>>>   head commit : a7a8993bfe3ccb54ad468b9f1799649e4ad1ff12
>>>   base commit : ba98a1cdad71d259a194461b3a61471b49b14df1
>>> Benchmark: will-it-scale
>>> Download link: https://github.com/antonblanchard/will-it-scale/tree/master
>>>
>>> Metrics:
>>>   will-it-scale.per_process_ops=processes/nr_cpu
>>>   will-it-scale.per_thread_ops=threads/nr_cpu
>>>   test box: lkp-skl-4sp1(nr_cpu=192,memory=768G)
>>> THP: enable / disable
>>> nr_task:100%
>>>
>>> 1. Regressions:
>>>
>>> a). Enable THP
>>> testcase                          base           change      head           metric
>>> page_fault3/enable THP           10519          -20.5%        836      will-it-scale.per_thread_ops
>>> page_fault2/enalbe THP            8281          -18.8%       6728      will-it-scale.per_thread_ops
>>> brk1/eanble THP                 998475           -2.2%     976893      will-it-scale.per_process_ops
>>> context_switch1/enable THP      223910           -1.3%     220930      will-it-scale.per_process_ops
>>> context_switch1/enable THP      233722           -1.0%     231288      will-it-scale.per_thread_ops
>>>
>>> b). Disable THP
>>> page_fault3/disable THP          10856          -23.1%       8344      will-it-scale.per_thread_ops
>>> page_fault2/disable THP           8147          -18.8%       6613      will-it-scale.per_thread_ops
>>> brk1/disable THP                   957           -7.9%        881      will-it-scale.per_thread_ops
>>> context_switch1/disable THP     237006           -2.2%     231907      will-it-scale.per_thread_ops
>>> brk1/disable THP                997317           -2.0%     977778      will-it-scale.per_process_ops
>>> page_fault3/disable THP         467454           -1.8%     459251      will-it-scale.per_process_ops
>>> context_switch1/disable THP     224431           -1.3%     221567      will-it-scale.per_process_ops
>>>
>>> Notes: for the above  values of test result, the higher is better.
>>
>> I tried the same tests on my PowerPC victim VM (1024 CPUs, 11TB) and I can't
>> get reproducible results. The results have huge variation, even on the vanilla
>> kernel, and I can't state on any changes due to that.
>>
>> I tried on smaller node (80 CPUs, 32G), and the tests ran better, but I didn't
>> measure any changes between the vanilla and the SPF patched ones:
>>
>> test THP enabled                4.17.0-rc4-mm1  spf             delta
>> page_fault3_threads             2697.7          2683.5          -0.53%
>> page_fault2_threads             170660.6        169574.1        -0.64%
>> context_switch1_threads         6915269.2       6877507.3       -0.55%
>> context_switch1_processes       6478076.2       6529493.5       0.79%
>> brk1                            243391.2        238527.5        -2.00%
>>
>> Tests were run 10 times, no high variation detected.
>>
>> Did you see high variation on your side ? How many times the test were run to
>> compute the average values ?
>>
>> Thanks,
>> Laurent.
>>
>>
>>>
>>> 2. Improvement: not found improvement based on the selected test cases.
>>>
>>>
>>> Best regards
>>> Haiyan Song
>>> ________________________________________
>>> From: owner-linux-mm at kvack.org [owner-linux-mm at kvack.org] on behalf of Laurent Dufour [ldufour at linux.vnet.ibm.com]
>>> Sent: Monday, May 28, 2018 4:54 PM
>>> To: Song, HaiyanX
>>> Cc: akpm at linux-foundation.org; mhocko at kernel.org; peterz at infradead.org; kirill at shutemov.name; ak at linux.intel.com; dave at stgolabs.net; jack at suse.cz; Matthew Wilcox; khandual at linux.vnet.ibm.com; aneesh.kumar at linux.vnet.ibm.com; benh at kernel.crashing.org; mpe at ellerman.id.au; paulus at samba.org; Thomas Gleixner; Ingo Molnar; hpa at zytor.com; Will Deacon; Sergey Senozhatsky; sergey.senozhatsky.work at gmail.com; Andrea Arcangeli; Alexei Starovoitov; Wang, Kemi; Daniel Jordan; David Rientjes; Jerome Glisse; Ganesh Mahendran; Minchan Kim; Punit Agrawal; vinayak menon; Yang Shi; linux-kernel at vger.kernel.org; linux-mm at kvack.org; haren at linux.vnet.ibm.com; npiggin at gmail.com; bsingharora at gmail.com; paulmck at linux.vnet.ibm.com; Tim Chen; linuxppc-dev at lists.ozlabs.org; x86 at kernel.org
>>> Subject: Re: [PATCH v11 00/26] Speculative page faults
>>>
>>> On 28/05/2018 10:22, Haiyan Song wrote:
>>>> Hi Laurent,
>>>>
>>>> Yes, these tests are done on V9 patch.
>>>
>>> Do you plan to give this V11 a run ?
>>>
>>>>
>>>>
>>>> Best regards,
>>>> Haiyan Song
>>>>
>>>> On Mon, May 28, 2018 at 09:51:34AM +0200, Laurent Dufour wrote:
>>>>> On 28/05/2018 07:23, Song, HaiyanX wrote:
>>>>>>
>>>>>> Some regression and improvements is found by LKP-tools(linux kernel performance) on V9 patch series
>>>>>> tested on Intel 4s Skylake platform.
>>>>>
>>>>> Hi,
>>>>>
>>>>> Thanks for reporting this benchmark results, but you mentioned the "V9 patch
>>>>> series" while responding to the v11 header series...
>>>>> Were these tests done on v9 or v11 ?
>>>>>
>>>>> Cheers,
>>>>> Laurent.
>>>>>
>>>>>>
>>>>>> The regression result is sorted by the metric will-it-scale.per_thread_ops.
>>>>>> Branch: Laurent-Dufour/Speculative-page-faults/20180316-151833 (V9 patch series)
>>>>>> Commit id:
>>>>>>     base commit: d55f34411b1b126429a823d06c3124c16283231f
>>>>>>     head commit: 0355322b3577eeab7669066df42c550a56801110
>>>>>> Benchmark suite: will-it-scale
>>>>>> Download link:
>>>>>> https://github.com/antonblanchard/will-it-scale/tree/master/tests
>>>>>> Metrics:
>>>>>>     will-it-scale.per_process_ops=processes/nr_cpu
>>>>>>     will-it-scale.per_thread_ops=threads/nr_cpu
>>>>>> test box: lkp-skl-4sp1(nr_cpu=192,memory=768G)
>>>>>> THP: enable / disable
>>>>>> nr_task: 100%
>>>>>>
>>>>>> 1. Regressions:
>>>>>> a) THP enabled:
>>>>>> testcase                        base            change          head       metric
>>>>>> page_fault3/ enable THP         10092           -17.5%          8323       will-it-scale.per_thread_ops
>>>>>> page_fault2/ enable THP          8300           -17.2%          6869       will-it-scale.per_thread_ops
>>>>>> brk1/ enable THP                  957.67         -7.6%           885       will-it-scale.per_thread_ops
>>>>>> page_fault3/ enable THP        172821            -5.3%        163692       will-it-scale.per_process_ops
>>>>>> signal1/ enable THP              9125            -3.2%          8834       will-it-scale.per_process_ops
>>>>>>
>>>>>> b) THP disabled:
>>>>>> testcase                        base            change          head       metric
>>>>>> page_fault3/ disable THP        10107           -19.1%          8180       will-it-scale.per_thread_ops
>>>>>> page_fault2/ disable THP         8432           -17.8%          6931       will-it-scale.per_thread_ops
>>>>>> context_switch1/ disable THP   215389            -6.8%        200776       will-it-scale.per_thread_ops
>>>>>> brk1/ disable THP                 939.67         -6.6%           877.33    will-it-scale.per_thread_ops
>>>>>> page_fault3/ disable THP       173145            -4.7%        165064       will-it-scale.per_process_ops
>>>>>> signal1/ disable THP             9162            -3.9%          8802       will-it-scale.per_process_ops
>>>>>>
>>>>>> 2. Improvements:
>>>>>> a) THP enabled:
>>>>>> testcase                        base            change          head       metric
>>>>>> malloc1/ enable THP               66.33        +469.8%           383.67    will-it-scale.per_thread_ops
>>>>>> writeseek3/ enable THP          2531             +4.5%          2646       will-it-scale.per_thread_ops
>>>>>> signal1/ enable THP              989.33          +2.8%          1016       will-it-scale.per_thread_ops
>>>>>>
>>>>>> b) THP disabled:
>>>>>> testcase                        base            change          head       metric
>>>>>> malloc1/ disable THP              90.33        +417.3%           467.33    will-it-scale.per_thread_ops
>>>>>> read2/ disable THP             58934            +39.2%         82060       will-it-scale.per_thread_ops
>>>>>> page_fault1/ disable THP        8607            +36.4%         11736       will-it-scale.per_thread_ops
>>>>>> read1/ disable THP            314063            +12.7%        353934       will-it-scale.per_thread_ops
>>>>>> writeseek3/ disable THP         2452            +12.5%          2759       will-it-scale.per_thread_ops
>>>>>> signal1/ disable THP             971.33          +5.5%          1024       will-it-scale.per_thread_ops
>>>>>>
>>>>>> Notes: for above values in column "change", the higher value means that the related testcase result
>>>>>> on head commit is better than that on base commit for this benchmark.
>>>>>>
>>>>>>
>>>>>> Best regards
>>>>>> Haiyan Song
>>>>>>
>>>>>> ________________________________________
>>>>>> From: owner-linux-mm at kvack.org [owner-linux-mm at kvack.org] on behalf of Laurent Dufour [ldufour at linux.vnet.ibm.com]
>>>>>> Sent: Thursday, May 17, 2018 7:06 PM
>>>>>> To: akpm at linux-foundation.org; mhocko at kernel.org; peterz at infradead.org; kirill at shutemov.name; ak at linux.intel.com; dave at stgolabs.net; jack at suse.cz; Matthew Wilcox; khandual at linux.vnet.ibm.com; aneesh.kumar at linux.vnet.ibm.com; benh at kernel.crashing.org; mpe at ellerman.id.au; paulus at samba.org; Thomas Gleixner; Ingo Molnar; hpa at zytor.com; Will Deacon; Sergey Senozhatsky; sergey.senozhatsky.work at gmail.com; Andrea Arcangeli; Alexei Starovoitov; Wang, Kemi; Daniel Jordan; David Rientjes; Jerome Glisse; Ganesh Mahendran; Minchan Kim; Punit Agrawal; vinayak menon; Yang Shi
>>>>>> Cc: linux-kernel at vger.kernel.org; linux-mm at kvack.org; haren at linux.vnet.ibm.com; npiggin at gmail.com; bsingharora at gmail.com; paulmck at linux.vnet.ibm.com; Tim Chen; linuxppc-dev at lists.ozlabs.org; x86 at kernel.org
>>>>>> Subject: [PATCH v11 00/26] Speculative page faults
>>>>>>
>>>>>> This is a port on kernel 4.17 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, this is done by introducing a rwlock
>>>>>> which protects the access to the mm_rb tree. Previously this was done using
>>>>>> SRCU but it was introducing a lot of scheduling to process the VMA's
>>>>>> freeing operation which was hitting the performance by 20% as reported by
>>>>>> Kemi Wang [2]. Using a rwlock to protect access to the mm_rb tree is
>>>>>> limiting the locking contention to these operations which are expected to
>>>>>> be in a O(log n) order. In addition to ensure that the VMA is not freed in
>>>>>> our back a reference count is added and 2 services (get_vma() and
>>>>>> put_vma()) are introduced to handle the reference count. Once a VMA is
>>>>>> fetched from the RB tree using get_vma(), it must be later freed using
>>>>>> put_vma(). I can't see anymore the overhead I got while will-it-scale
>>>>>> benchmark anymore.
>>>>>>
>>>>>> 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 has been 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 lockings 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.
>>>>>>
>>>>>> The locking of the PTE is done with interrupts disabled, this allows
>>>>>> checking for the PMD to ensure that there is not an ongoing collapsing
>>>>>> operation. Since khugepaged is firstly set the PMD to pmd_none and then is
>>>>>> waiting for the other CPU to have caught the IPI interrupt, if the pmd is
>>>>>> valid at the time the PTE is locked, we have the guarantee that the
>>>>>> collapsing operation will have to wait on the PTE lock to move forward.
>>>>>> This allows the SPF handler to map the PTE safely. If the PMD value is
>>>>>> different from the one recorded at the beginning of the SPF operation, the
>>>>>> classic page fault handler will be called to handle the operation while
>>>>>> holding the mmap_sem. As the PTE lock is done with the interrupts disabled,
>>>>>> the lock is done using spin_trylock() to avoid dead lock when handling a
>>>>>> page fault while a TLB invalidate is requested by another CPU holding the
>>>>>> PTE.
>>>>>>
>>>>>> In pseudo code, this could be seen as:
>>>>>>     speculative_page_fault()
>>>>>>     {
>>>>>>             vma = get_vma()
>>>>>>             check vma sequence count
>>>>>>             check vma's support
>>>>>>             disable interrupt
>>>>>>                   check pgd,p4d,...,pte
>>>>>>                   save pmd and pte in vmf
>>>>>>                   save vma sequence counter in vmf
>>>>>>             enable interrupt
>>>>>>             check vma sequence count
>>>>>>             handle_pte_fault(vma)
>>>>>>                     ..
>>>>>>                     page = alloc_page()
>>>>>>                     pte_map_lock()
>>>>>>                             disable interrupt
>>>>>>                                     abort if sequence counter has changed
>>>>>>                                     abort if pmd or pte has changed
>>>>>>                                     pte map and lock
>>>>>>                             enable interrupt
>>>>>>                     if abort
>>>>>>                        free page
>>>>>>                        abort
>>>>>>                     ...
>>>>>>     }
>>>>>>
>>>>>>     arch_fault_handler()
>>>>>>     {
>>>>>>             if (speculative_page_fault(&vma))
>>>>>>                goto done
>>>>>>     again:
>>>>>>             lock(mmap_sem)
>>>>>>             vma = find_vma();
>>>>>>             handle_pte_fault(vma);
>>>>>>             if retry
>>>>>>                unlock(mmap_sem)
>>>>>>                goto again;
>>>>>>     done:
>>>>>>             handle fault error
>>>>>>     }
>>>>>>
>>>>>> Support for THP is not done because when checking for the PMD, we can be
>>>>>> confused by an in progress collapsing operation done by khugepaged. The
>>>>>> issue is that pmd_none() could be true either if the PMD is not already
>>>>>> populated or if the underlying PTE are in the way to be collapsed. So we
>>>>>> cannot safely allocate a PMD if pmd_none() is true.
>>>>>>
>>>>>> This series add a new software performance event named 'speculative-faults'
>>>>>> or 'spf'. It counts the number of successful page fault event handled
>>>>>> speculatively. When recording 'faults,spf' events, the faults one is
>>>>>> counting the total number of page fault events while 'spf' is only counting
>>>>>> the part of the faults processed speculatively.
>>>>>>
>>>>>> There are some trace events introduced by this series. They allow
>>>>>> identifying why the page faults were not processed speculatively. This
>>>>>> doesn't take in account the faults generated by a monothreaded process
>>>>>> which directly processed while holding the mmap_sem. This trace events are
>>>>>> grouped in a system named 'pagefault', they are:
>>>>>>  - pagefault:spf_vma_changed : if the VMA has been changed in our back
>>>>>>  - pagefault:spf_vma_noanon : the vma->anon_vma field was not yet set.
>>>>>>  - pagefault:spf_vma_notsup : the VMA's type is not supported
>>>>>>  - pagefault:spf_vma_access : the VMA's access right are not respected
>>>>>>  - pagefault:spf_pmd_changed : the upper PMD pointer has changed in our
>>>>>>    back.
>>>>>>
>>>>>> To record all the related events, the easier is to run perf with the
>>>>>> following arguments :
>>>>>> $ perf stat -e 'faults,spf,pagefault:*' <command>
>>>>>>
>>>>>> There is also a dedicated vmstat counter showing the number of successful
>>>>>> page fault handled speculatively. I can be seen this way:
>>>>>> $ grep speculative_pgfault /proc/vmstat
>>>>>>
>>>>>> This series builds on top of v4.16-mmotm-2018-04-13-17-28 and is functional
>>>>>> on x86, PowerPC and arm64.
>>>>>>
>>>>>> ---------------------
>>>>>> Real Workload results
>>>>>>
>>>>>> As mentioned in previous email, we did non official runs using a "popular
>>>>>> in memory multithreaded database product" on 176 cores SMT8 Power system
>>>>>> which showed a 30% improvements in the number of transaction processed per
>>>>>> second. This run has been done on the v6 series, but changes introduced in
>>>>>> this new version should not impact the performance boost seen.
>>>>>>
>>>>>> Here are the perf data captured during 2 of these runs on top of the v8
>>>>>> series:
>>>>>>                 vanilla         spf
>>>>>> faults          89.418          101.364         +13%
>>>>>> spf                n/a           97.989
>>>>>>
>>>>>> With the SPF kernel, most of the page fault were processed in a speculative
>>>>>> way.
>>>>>>
>>>>>> Ganesh Mahendran had backported the series on top of a 4.9 kernel and gave
>>>>>> it a try on an android device. He reported that the application launch time
>>>>>> was improved in average by 6%, and for large applications (~100 threads) by
>>>>>> 20%.
>>>>>>
>>>>>> Here are the launch time Ganesh mesured on Android 8.0 on top of a Qcom
>>>>>> MSM845 (8 cores) with 6GB (the less is better):
>>>>>>
>>>>>> Application                             4.9     4.9+spf delta
>>>>>> com.tencent.mm                          416     389     -7%
>>>>>> com.eg.android.AlipayGphone             1135    986     -13%
>>>>>> com.tencent.mtt                         455     454     0%
>>>>>> com.qqgame.hlddz                        1497    1409    -6%
>>>>>> com.autonavi.minimap                    711     701     -1%
>>>>>> com.tencent.tmgp.sgame                  788     748     -5%
>>>>>> com.immomo.momo                         501     487     -3%
>>>>>> com.tencent.peng                        2145    2112    -2%
>>>>>> com.smile.gifmaker                      491     461     -6%
>>>>>> com.baidu.BaiduMap                      479     366     -23%
>>>>>> com.taobao.taobao                       1341    1198    -11%
>>>>>> com.baidu.searchbox                     333     314     -6%
>>>>>> com.tencent.mobileqq                    394     384     -3%
>>>>>> com.sina.weibo                          907     906     0%
>>>>>> com.youku.phone                         816     731     -11%
>>>>>> com.happyelements.AndroidAnimal.qq      763     717     -6%
>>>>>> com.UCMobile                            415     411     -1%
>>>>>> com.tencent.tmgp.ak                     1464    1431    -2%
>>>>>> com.tencent.qqmusic                     336     329     -2%
>>>>>> com.sankuai.meituan                     1661    1302    -22%
>>>>>> com.netease.cloudmusic                  1193    1200    1%
>>>>>> air.tv.douyu.android                    4257    4152    -2%
>>>>>>
>>>>>> ------------------
>>>>>> Benchmarks results
>>>>>>
>>>>>> Base kernel is v4.17.0-rc4-mm1
>>>>>> SPF is BASE + this series
>>>>>>
>>>>>> Kernbench:
>>>>>> ----------
>>>>>> Here are the results on a 16 CPUs X86 guest using kernbench on a 4.15
>>>>>> kernel (kernel is build 5 times):
>>>>>>
>>>>>> Average Half load -j 8
>>>>>>                  Run    (std deviation)
>>>>>>                  BASE                   SPF
>>>>>> Elapsed Time     1448.65 (5.72312)      1455.84 (4.84951)       0.50%
>>>>>> User    Time     10135.4 (30.3699)      10148.8 (31.1252)       0.13%
>>>>>> System  Time     900.47  (2.81131)      923.28  (7.52779)       2.53%
>>>>>> Percent CPU      761.4   (1.14018)      760.2   (0.447214)      -0.16%
>>>>>> Context Switches 85380   (3419.52)      84748   (1904.44)       -0.74%
>>>>>> Sleeps           105064  (1240.96)      105074  (337.612)       0.01%
>>>>>>
>>>>>> Average Optimal load -j 16
>>>>>>                  Run    (std deviation)
>>>>>>                  BASE                   SPF
>>>>>> Elapsed Time     920.528 (10.1212)      927.404 (8.91789)       0.75%
>>>>>> User    Time     11064.8 (981.142)      11085   (990.897)       0.18%
>>>>>> System  Time     979.904 (84.0615)      1001.14 (82.5523)       2.17%
>>>>>> Percent CPU      1089.5  (345.894)      1086.1  (343.545)       -0.31%
>>>>>> Context Switches 159488  (78156.4)      158223  (77472.1)       -0.79%
>>>>>> Sleeps           110566  (5877.49)      110388  (5617.75)       -0.16%
>>>>>>
>>>>>>
>>>>>> During a run on the SPF, perf events were captured:
>>>>>>  Performance counter stats for '../kernbench -M':
>>>>>>          526743764      faults
>>>>>>                210      spf
>>>>>>                  3      pagefault:spf_vma_changed
>>>>>>                  0      pagefault:spf_vma_noanon
>>>>>>               2278      pagefault:spf_vma_notsup
>>>>>>                  0      pagefault:spf_vma_access
>>>>>>                  0      pagefault:spf_pmd_changed
>>>>>>
>>>>>> Very few speculative page faults were recorded as most of the processes
>>>>>> involved are monothreaded (sounds that on this architecture some threads
>>>>>> were created during the kernel build processing).
>>>>>>
>>>>>> Here are the kerbench results on a 80 CPUs Power8 system:
>>>>>>
>>>>>> Average Half load -j 40
>>>>>>                  Run    (std deviation)
>>>>>>                  BASE                   SPF
>>>>>> Elapsed Time     117.152 (0.774642)     117.166 (0.476057)      0.01%
>>>>>> User    Time     4478.52 (24.7688)      4479.76 (9.08555)       0.03%
>>>>>> System  Time     131.104 (0.720056)     134.04  (0.708414)      2.24%
>>>>>> Percent CPU      3934    (19.7104)      3937.2  (19.0184)       0.08%
>>>>>> Context Switches 92125.4 (576.787)      92581.6 (198.622)       0.50%
>>>>>> Sleeps           317923  (652.499)      318469  (1255.59)       0.17%
>>>>>>
>>>>>> Average Optimal load -j 80
>>>>>>                  Run    (std deviation)
>>>>>>                  BASE                   SPF
>>>>>> Elapsed Time     107.73  (0.632416)     107.31  (0.584936)      -0.39%
>>>>>> User    Time     5869.86 (1466.72)      5871.71 (1467.27)       0.03%
>>>>>> System  Time     153.728 (23.8573)      157.153 (24.3704)       2.23%
>>>>>> Percent CPU      5418.6  (1565.17)      5436.7  (1580.91)       0.33%
>>>>>> Context Switches 223861  (138865)       225032  (139632)        0.52%
>>>>>> Sleeps           330529  (13495.1)      332001  (14746.2)       0.45%
>>>>>>
>>>>>> During a run on the SPF, perf events were captured:
>>>>>>  Performance counter stats for '../kernbench -M':
>>>>>>          116730856      faults
>>>>>>                  0      spf
>>>>>>                  3      pagefault:spf_vma_changed
>>>>>>                  0      pagefault:spf_vma_noanon
>>>>>>                476      pagefault:spf_vma_notsup
>>>>>>                  0      pagefault:spf_vma_access
>>>>>>                  0      pagefault:spf_pmd_changed
>>>>>>
>>>>>> Most of the processes involved are monothreaded so SPF is not activated but
>>>>>> there is no impact on the performance.
>>>>>>
>>>>>> 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 -mTt <nrcpus>'. To get
>>>>>> consistent result I repeated the test 100 times and measure the average
>>>>>> result. The number is the record processes per second, the higher is the
>>>>>> best.
>>>>>>
>>>>>>                 BASE            SPF             delta
>>>>>> 16 CPUs x86 VM  742.57          1490.24         100.69%
>>>>>> 80 CPUs P8 node 13105.4         24174.23        84.46%
>>>>>>
>>>>>> Here are the performance counter read during a run on a 16 CPUs x86 VM:
>>>>>>  Performance counter stats for './ebizzy -mTt 16':
>>>>>>            1706379      faults
>>>>>>            1674599      spf
>>>>>>              30588      pagefault:spf_vma_changed
>>>>>>                  0      pagefault:spf_vma_noanon
>>>>>>                363      pagefault:spf_vma_notsup
>>>>>>                  0      pagefault:spf_vma_access
>>>>>>                  0      pagefault:spf_pmd_changed
>>>>>>
>>>>>> And the ones captured during a run on a 80 CPUs Power node:
>>>>>>  Performance counter stats for './ebizzy -mTt 80':
>>>>>>            1874773      faults
>>>>>>            1461153      spf
>>>>>>             413293      pagefault:spf_vma_changed
>>>>>>                  0      pagefault:spf_vma_noanon
>>>>>>                200      pagefault:spf_vma_notsup
>>>>>>                  0      pagefault:spf_vma_access
>>>>>>                  0      pagefault:spf_pmd_changed
>>>>>>
>>>>>> In ebizzy's case most of the page fault were handled in a speculative way,
>>>>>> leading the ebizzy performance boost.
>>>>>>
>>>>>> ------------------
>>>>>> Changes since v10 (https://lkml.org/lkml/2018/4/17/572):
>>>>>>  - Accounted for all review feedbacks from Punit Agrawal, Ganesh Mahendran
>>>>>>    and Minchan Kim, hopefully.
>>>>>>  - Remove unneeded check on CONFIG_SPECULATIVE_PAGE_FAULT in
>>>>>>    __do_page_fault().
>>>>>>  - Loop in pte_spinlock() and pte_map_lock() when pte try lock fails
>>>>>>    instead
>>>>>>    of aborting the speculative page fault handling. Dropping the now
>>>>>> useless
>>>>>>    trace event pagefault:spf_pte_lock.
>>>>>>  - No more try to reuse the fetched VMA during the speculative page fault
>>>>>>    handling when retrying is needed. This adds a lot of complexity and
>>>>>>    additional tests done didn't show a significant performance improvement.
>>>>>>  - Convert IS_ENABLED(CONFIG_NUMA) back to #ifdef due to build error.
>>>>>>
>>>>>> [1] http://linux-kernel.2935.n7.nabble.com/RFC-PATCH-0-6-Another-go-at-speculative-page-faults-tt965642.html#none
>>>>>> [2] https://patchwork.kernel.org/patch/9999687/
>>>>>>
>>>>>>
>>>>>> Laurent Dufour (20):
>>>>>>   mm: introduce CONFIG_SPECULATIVE_PAGE_FAULT
>>>>>>   x86/mm: define ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT
>>>>>>   powerpc/mm: set ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT
>>>>>>   mm: introduce pte_spinlock for FAULT_FLAG_SPECULATIVE
>>>>>>   mm: make pte_unmap_same compatible with SPF
>>>>>>   mm: introduce INIT_VMA()
>>>>>>   mm: protect VMA modifications using VMA sequence count
>>>>>>   mm: protect mremap() against SPF hanlder
>>>>>>   mm: protect SPF handler against anon_vma changes
>>>>>>   mm: cache some VMA fields in the vm_fault structure
>>>>>>   mm/migrate: Pass vm_fault pointer to migrate_misplaced_page()
>>>>>>   mm: introduce __lru_cache_add_active_or_unevictable
>>>>>>   mm: introduce __vm_normal_page()
>>>>>>   mm: introduce __page_add_new_anon_rmap()
>>>>>>   mm: protect mm_rb tree with a rwlock
>>>>>>   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
>>>>>>   mm: add speculative page fault vmstats
>>>>>>   powerpc/mm: add speculative page fault
>>>>>>
>>>>>> Mahendran Ganesh (2):
>>>>>>   arm64/mm: define ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT
>>>>>>   arm64/mm: add speculative page fault
>>>>>>
>>>>>> Peter Zijlstra (4):
>>>>>>   mm: prepare for FAULT_FLAG_SPECULATIVE
>>>>>>   mm: VMA sequence count
>>>>>>   mm: provide speculative fault infrastructure
>>>>>>   x86/mm: add speculative pagefault handling
>>>>>>
>>>>>>  arch/arm64/Kconfig                    |   1 +
>>>>>>  arch/arm64/mm/fault.c                 |  12 +
>>>>>>  arch/powerpc/Kconfig                  |   1 +
>>>>>>  arch/powerpc/mm/fault.c               |  16 +
>>>>>>  arch/x86/Kconfig                      |   1 +
>>>>>>  arch/x86/mm/fault.c                   |  27 +-
>>>>>>  fs/exec.c                             |   2 +-
>>>>>>  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                    | 136 +++++++-
>>>>>>  include/linux/mm_types.h              |   7 +
>>>>>>  include/linux/pagemap.h               |   4 +-
>>>>>>  include/linux/rmap.h                  |  12 +-
>>>>>>  include/linux/swap.h                  |  10 +-
>>>>>>  include/linux/vm_event_item.h         |   3 +
>>>>>>  include/trace/events/pagefault.h      |  80 +++++
>>>>>>  include/uapi/linux/perf_event.h       |   1 +
>>>>>>  kernel/fork.c                         |   5 +-
>>>>>>  mm/Kconfig                            |  22 ++
>>>>>>  mm/huge_memory.c                      |   6 +-
>>>>>>  mm/hugetlb.c                          |   2 +
>>>>>>  mm/init-mm.c                          |   3 +
>>>>>>  mm/internal.h                         |  20 ++
>>>>>>  mm/khugepaged.c                       |   5 +
>>>>>>  mm/madvise.c                          |   6 +-
>>>>>>  mm/memory.c                           | 612 +++++++++++++++++++++++++++++-----
>>>>>>  mm/mempolicy.c                        |  51 ++-
>>>>>>  mm/migrate.c                          |   6 +-
>>>>>>  mm/mlock.c                            |  13 +-
>>>>>>  mm/mmap.c                             | 229 ++++++++++---
>>>>>>  mm/mprotect.c                         |   4 +-
>>>>>>  mm/mremap.c                           |  13 +
>>>>>>  mm/nommu.c                            |   2 +-
>>>>>>  mm/rmap.c                             |   5 +-
>>>>>>  mm/swap.c                             |   6 +-
>>>>>>  mm/swap_state.c                       |   8 +-
>>>>>>  mm/vmstat.c                           |   5 +-
>>>>>>  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 +
>>>>>>  44 files changed, 1161 insertions(+), 211 deletions(-)
>>>>>>  create mode 100644 include/trace/events/pagefault.h
>>>>>>
>>>>>> --
>>>>>> 2.7.4
>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>>
>

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