Re: [PATCH v11 00/26] Speculative page faults

[Laurent Dufour <ldufour@linux.vnet.ibm.com>]

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      A+- 3%        -20.5%      8368      A+-6%          will-it-scale.per_thread_ops
> page_fault2/enalbe THP            8281      A+- 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@linux.vnet.ibm.com]
> Sent: Monday, July 02, 2018 4:59 PM
> To: Song, HaiyanX
> Cc: 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; khandual@linux.vnet.ibm.com; aneesh.kumar@linux.vnet.ibm.com; benh@kernel.crashing.org; mpe@ellerman.id.au; paulus@samba.org; Thomas Gleixner; Ingo Molnar; hpa@zytor.com; Will Deacon; Sergey Senozhatsky; sergey.senozhatsky.work@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@vger.kernel.org; linux-mm@kvack.org; haren@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: 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@kvack.org [owner-linux-mm@kvack.org] on behalf of Laurent Dufour [ldufour@linux.vnet.ibm.com]
>> Sent: Monday, May 28, 2018 4:54 PM
>> To: Song, HaiyanX
>> Cc: 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; khandual@linux.vnet.ibm.com; aneesh.kumar@linux.vnet.ibm.com; benh@kernel.crashing.org; mpe@ellerman.id.au; paulus@samba.org; Thomas Gleixner; Ingo Molnar; hpa@zytor.com; Will Deacon; Sergey Senozhatsky; sergey.senozhatsky.work@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@vger.kernel.org; linux-mm@kvack.org; haren@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: 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@kvack.org [owner-linux-mm@kvack.org] on behalf of Laurent Dufour [ldufour@linux.vnet.ibm.com]
>>>>> Sent: Thursday, May 17, 2018 7:06 PM
>>>>> 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; khandual@linux.vnet.ibm.com; aneesh.kumar@linux.vnet.ibm.com; benh@kernel.crashing.org; mpe@ellerman.id.au; paulus@samba.org; Thomas Gleixner; Ingo Molnar; hpa@zytor.com; Will Deacon; Sergey Senozhatsky; sergey.senozhatsky.work@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@vger.kernel.org; linux-mm@kvack.org; haren@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 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
>>>>>
>>>>>
>>>>
>>>
>>
> 
>