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Subject: Re: [RFC][PATCH v2 00/21] x86/pti: Defer CR3 switch to C code
To:     Borislav Petkov <bp@alien8.de>
Cc:     tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
        x86@kernel.org, dave.hansen@linux.intel.com, luto@kernel.org,
        peterz@infradead.org, linux-kernel@vger.kernel.org,
        thomas.lendacky@amd.com, jroedel@suse.de, konrad.wilk@oracle.com,
        jan.setjeeilers@oracle.com, junaids@google.com, oweisse@google.com,
        rppt@linux.vnet.ibm.com, graf@amazon.de, mgross@linux.intel.com,
        kuzuno@gmail.com, Mel Gorman <mgorman@techsingularity.net>
References: <20201116144757.1920077-1-alexandre.chartre@oracle.com>
 <20201116201711.GE1131@zn.tnic>
 <44a88648-738a-4a4b-9c25-6b70000e037c@oracle.com>
 <20201117165539.GG5719@zn.tnic>
 <890f6b7e-a268-2257-edcb-5eacc7db3d8e@oracle.com>
 <20201117212608.GS5719@zn.tnic>
 <b63ec614-8a49-728d-aa61-76339378183f@oracle.com>
 <20201118112952.GB7472@zn.tnic>
From:   Alexandre Chartre <alexandre.chartre@oracle.com>
Message-ID: <408004fa-b143-7e12-150a-0dfab12d34ee@oracle.com>
Date:   Wed, 18 Nov 2020 20:37:57 +0100
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On 11/18/20 12:29 PM, Borislav Petkov wrote:
> On Wed, Nov 18, 2020 at 08:41:42AM +0100, Alexandre Chartre wrote:
>> Well, it looks like I wrongfully assume that KPTI was a well known performance
>> overhead since it was introduced (because it adds extra page-table switches),
>> but you are right I should be presenting my own numbers.
> 
> Here's one recipe, courtesy of Mel:
> 
> https://github.com/gormanm/mmtests
> 

Thanks for the detailed information, I have run the test and I see the same difference
as with the tools/perf and libMICRO I already sent: there's a 150% difference for
getpid() with and without pti.

alex.

-----

# ../../compare-kernels.sh --baseline test-nopti --compare test-pti

poundsyscall
                                test                   test
                               nopti                    pti
Min       2         1.99 (   0.00%)        5.08 (-155.28%)
Min       4         1.02 (   0.00%)        2.60 (-154.90%)
Min       6         0.94 (   0.00%)        2.07 (-120.21%)
Min       8         0.81 (   0.00%)        1.60 ( -97.53%)
Min       12        0.85 (   0.00%)        1.65 ( -94.12%)
Min       18        0.82 (   0.00%)        1.61 ( -96.34%)
Min       24        0.81 (   0.00%)        1.60 ( -97.53%)
Min       30        0.81 (   0.00%)        1.60 ( -97.53%)
Min       32        0.81 (   0.00%)        1.60 ( -97.53%)
Amean     2         2.02 (   0.00%)        5.10 *-151.83%*
Amean     4         1.03 (   0.00%)        2.61 *-151.98%*
Amean     6         0.96 (   0.00%)        2.07 *-116.74%*
Amean     8         0.82 (   0.00%)        1.60 * -96.56%*
Amean     12        0.87 (   0.00%)        1.67 * -91.73%*
Amean     18        0.82 (   0.00%)        1.63 * -97.94%*
Amean     24        0.81 (   0.00%)        1.60 * -97.41%*
Amean     30        0.82 (   0.00%)        1.60 * -96.93%*
Amean     32        0.82 (   0.00%)        1.60 * -96.56%*
Stddev    2         0.02 (   0.00%)        0.02 (  33.78%)
Stddev    4         0.01 (   0.00%)        0.01 (   7.18%)
Stddev    6         0.01 (   0.00%)        0.00 (  68.77%)
Stddev    8         0.01 (   0.00%)        0.01 (  10.56%)
Stddev    12        0.01 (   0.00%)        0.02 ( -12.69%)
Stddev    18        0.01 (   0.00%)        0.01 (-107.25%)
Stddev    24        0.00 (   0.00%)        0.00 ( -14.56%)
Stddev    30        0.01 (   0.00%)        0.01 (   0.00%)
Stddev    32        0.01 (   0.00%)        0.00 (  20.00%)
CoeffVar  2         1.17 (   0.00%)        0.31 (  73.70%)
CoeffVar  4         0.82 (   0.00%)        0.30 (  63.16%)
CoeffVar  6         1.41 (   0.00%)        0.20 (  85.59%)
CoeffVar  8         0.87 (   0.00%)        0.39 (  54.50%)
CoeffVar  12        1.66 (   0.00%)        0.98 (  41.23%)
CoeffVar  18        0.85 (   0.00%)        0.89 (  -4.71%)
CoeffVar  24        0.52 (   0.00%)        0.30 (  41.97%)
CoeffVar  30        0.65 (   0.00%)        0.33 (  49.22%)
CoeffVar  32        0.65 (   0.00%)        0.26 (  59.30%)
Max       2         2.04 (   0.00%)        5.13 (-151.47%)
Max       4         1.04 (   0.00%)        2.62 (-151.92%)
Max       6         0.98 (   0.00%)        2.08 (-112.24%)
Max       8         0.83 (   0.00%)        1.62 ( -95.18%)
Max       12        0.89 (   0.00%)        1.70 ( -91.01%)
Max       18        0.84 (   0.00%)        1.66 ( -97.62%)
Max       24        0.82 (   0.00%)        1.61 ( -96.34%)
Max       30        0.82 (   0.00%)        1.61 ( -96.34%)
Max       32        0.82 (   0.00%)        1.61 ( -96.34%)
BAmean-50 2         2.01 (   0.00%)        5.09 (-153.39%)
BAmean-50 4         1.03 (   0.00%)        2.60 (-152.62%)
BAmean-50 6         0.95 (   0.00%)        2.07 (-118.82%)
BAmean-50 8         0.81 (   0.00%)        1.60 ( -97.53%)
BAmean-50 12        0.86 (   0.00%)        1.66 ( -92.79%)
BAmean-50 18        0.82 (   0.00%)        1.62 ( -97.56%)
BAmean-50 24        0.81 (   0.00%)        1.60 ( -97.53%)
BAmean-50 30        0.81 (   0.00%)        1.60 ( -97.53%)
BAmean-50 32        0.81 (   0.00%)        1.60 ( -97.53%)
BAmean-95 2         2.02 (   0.00%)        5.09 (-151.87%)
BAmean-95 4         1.03 (   0.00%)        2.61 (-151.99%)
BAmean-95 6         0.95 (   0.00%)        2.07 (-117.25%)
BAmean-95 8         0.81 (   0.00%)        1.60 ( -96.72%)
BAmean-95 12        0.87 (   0.00%)        1.67 ( -91.82%)
BAmean-95 18        0.82 (   0.00%)        1.63 ( -97.97%)
BAmean-95 24        0.81 (   0.00%)        1.60 ( -97.53%)
BAmean-95 30        0.81 (   0.00%)        1.60 ( -97.00%)
BAmean-95 32        0.81 (   0.00%)        1.60 ( -96.59%)
BAmean-99 2         2.02 (   0.00%)        5.09 (-151.87%)
BAmean-99 4         1.03 (   0.00%)        2.61 (-151.99%)
BAmean-99 6         0.95 (   0.00%)        2.07 (-117.25%)
BAmean-99 8         0.81 (   0.00%)        1.60 ( -96.72%)
BAmean-99 12        0.87 (   0.00%)        1.67 ( -91.82%)
BAmean-99 18        0.82 (   0.00%)        1.63 ( -97.97%)
BAmean-99 24        0.81 (   0.00%)        1.60 ( -97.53%)
BAmean-99 30        0.81 (   0.00%)        1.60 ( -97.00%)
BAmean-99 32        0.81 (   0.00%)        1.60 ( -96.59%)

                         test        test
                        nopti         pti
Duration User         150.13      432.03
Duration System       372.10      657.69
Duration Elapsed       94.17      199.27