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From:   Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
To:     lenb@kernel.org, rjw@rjwysocki.net, mgorman@techsingularity.net
Cc:     peterz@infradead.org, linux-pm@vger.kernel.org,
        linux-kernel@vger.kernel.org, juri.lelli@redhat.com,
        viresh.kumar@linaro.org, ggherdovich@suse.cz,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Subject: [PATCH 0/4] Intel_pstate: HWP Dynamic performance boost
Date:   Tue,  5 Jun 2018 14:42:38 -0700
Message-Id: <20180605214242.62156-1-srinivas.pandruvada@linux.intel.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

v1 (Compared to RFC/RFT v3)
- Minor suggestion for intel_pstate for coding
- Add SKL desktop model used in some Xeons

Tested-by: Giovanni Gherdovich <ggherdovich@suse.cz>

This series has an overall positive performance impact on IO both on xfs and
ext4, and I'd be vary happy if it lands in v4.18. You dropped the migration
optimization from v1 to v2 after the reviewers' suggestion; I'm looking
forward to test that part too, so please add me to CC when you'll resend it.

I've tested your series on a single socket Xeon E3-1240 v5 (Skylake, 4 cores /
8 threads) with SSD storage. The platform is a Dell PowerEdge R230.

The benchmarks used are a mix of I/O intensive workloads on ext4 and xfs
(dbench4, sqlite, pgbench in read/write and read-only configuration, Flexible
IO aka FIO, etc) and scheduler stressers just to check that everything is okay
in that department too (hackbench, pipetest, schbench, sockperf on localhost
both in "throughput" and "under-load" mode, netperf in localhost, etc). There
is also some HPC with the NAS Parallel Benchmark, as when using openMPI as IPC
mechanism it ends up being write-intensive and that could be a good
experiment, even if the HPC people aren't exactly the target audience for a
frequency governor.

The large improvements are in areas you already highlighted in your cover
letter (dbench4, sqlite, and pgbench read/write too, very impressive
honestly). Minor wins are also observed in sockperf and running the git unit
tests (gitsource below). The scheduler stressers ends up, as expected, in the
"neutral" category where you'll also find FIO (which given other results I'd
have expected to improve a little at least). Marked "neutral" are also those
results where statistical significance wasn't reached (2 standard deviations,
which is roughly like a 0.05 p-value) even if they showed some difference in a
direction or the other. In the "small losses" section I found hackbench run
with processes (not threads) and pipes (not sockets) which I report for due
diligence but looking at the raw numbers it's more of a mixed bag than a real
loss, and the NAS high-perf computing benchmark when it uses openMP (as
opposed to openMPI) for IPC -- but again, we often find that supercomputers
people run the machines at full speed all the time.

At the bottom of this message you'll find some directions if you want to run
some test yourself using the same framework I used, MMTests from
https://github.com/gormanm/mmtests (we store a fair amount of benchmarks
parametrization up there).

Large wins:

    - dbench4:              +20% on ext4,
                            +14% on xfs (always asynch IO)
    - sqlite (insert):       +9% on both ext4 and xfs
    - pgbench (read/write):  +9% on ext4,
                            +10% on xfs

Moderate wins:

    - sockperf (type: under-load, localhost):              +1% with TCP,
                                                           +5% with UDP
    - gisource (git unit tests, shell intensive):          +3% on ext4
    - NAS Parallel Benchmark (HPC, using openMPI, on xfs): +1%
    - tbench4 (network part of dbench4, localhost):        +1%

Neutral:

    - pgbench (read-only) on ext4 and xfs
    - siege
    - netperf (streaming and round-robin) with TCP and UDP
    - hackbench (sockets/process, sockets/thread and pipes/thread)
    - pipetest
    - Linux kernel build
    - schbench
    - sockperf (type: throughput) with TCP and UDP
    - git unit tests on xfs
    - FIO (both random and seq. read, both random and seq. write)
      on ext4 and xfs, async IO

Moderate losses:

    - hackbench (pipes/process):          -10%
    - NAS Parallel Benchmark with openMP:  -1%


Each benchmark is run with a variety of configuration parameters (eg: number
of threads, number of clients, etc); to reach a final "score" the geometric
mean is used (with a few exceptions depending on the type of benchmark).
Detailed results follow. Amean, Hmean and Gmean are respectively arithmetic,
harmonic and geometric means.

For brevity I won't report all tables but only those for "large wins" and
"moderate losses". Note that I'm not overly worried for the hackbench-pipes
situation, as we've studied it in the past and determined that such
configuration is particularly weak, time is mostly spent on contention and the
scheduler code path isn't exercised. See the comment in the file
configs/config-global-dhp__scheduler-unbound in MMTests for a brief
description of the issue.

DBENCH4
=======

NOTES: asyncronous IO; varies the number of clients up to NUMCPUS*8.
MMTESTS CONFIG: global-dhp__io-dbench4-async-{ext4, xfs}
MEASURES: latency (millisecs)
LOWER is better

EXT4
                              4.16.0                 4.16.0
                             vanilla              hwp-boost
Amean      1        28.49 (   0.00%)       19.68 (  30.92%)
Amean      2        26.70 (   0.00%)       25.59 (   4.14%)
Amean      4        54.59 (   0.00%)       43.56 (  20.20%)
Amean      8        91.19 (   0.00%)       77.56 (  14.96%)
Amean      64      538.09 (   0.00%)      438.67 (  18.48%)
Stddev     1         6.70 (   0.00%)        3.24 (  51.66%)
Stddev     2         4.35 (   0.00%)        3.57 (  17.85%)
Stddev     4         7.99 (   0.00%)        7.24 (   9.29%)
Stddev     8        17.51 (   0.00%)       15.80 (   9.78%)
Stddev     64       49.54 (   0.00%)       46.98 (   5.17%)

XFS
                              4.16.0                 4.16.0
                             vanilla              hwp-boost
Amean      1        21.88 (   0.00%)       16.03 (  26.75%)
Amean      2        19.72 (   0.00%)       19.82 (  -0.50%)
Amean      4        37.55 (   0.00%)       29.52 (  21.38%)
Amean      8        56.73 (   0.00%)       51.83 (   8.63%)
Amean      64      808.80 (   0.00%)      698.12 (  13.68%)
Stddev     1         6.29 (   0.00%)        2.33 (  62.99%)
Stddev     2         3.12 (   0.00%)        2.26 (  27.73%)
Stddev     4         7.56 (   0.00%)        5.88 (  22.28%)
Stddev     8        14.15 (   0.00%)       12.49 (  11.71%)
Stddev     64      380.54 (   0.00%)      367.88 (   3.33%)

SQLITE
======

NOTES: SQL insert test on a table that will be 2M in size.
MMTESTS CONFIG: global-dhp__db-sqlite-insert-medium-{ext4, xfs}
MEASURES: transactions per second
HIGHER is better

EXT4
                                4.16.0                 4.16.0
                               vanilla              hwp-boost
Hmean     Trans     2098.79 (   0.00%)     2292.16 (   9.21%)
Stddev    Trans       78.79 (   0.00%)       95.73 ( -21.50%)

XFS
                                4.16.0                 4.16.0
                               vanilla              hwp-boost
Hmean     Trans     1890.27 (   0.00%)     2058.62 (   8.91%)
Stddev    Trans       52.54 (   0.00%)       29.56 (  43.73%)

PGBENCH-RW
==========

NOTES: packaged with Postgres. Varies the number of thread up to NUMCPUS. The
  workload is scaled so that the approximate size is 80% of of the database
  shared buffer which itself is 20% of RAM. The page cache is not flushed
  after the database is populated for the test and starts cache-hot.
MMTESTS CONFIG: global-dhp__db-pgbench-timed-rw-small-{ext4, xfs}
MEASURES: transactions per second
HIGHER is better

EXT4
                            4.16.0                 4.16.0
                           vanilla              hwp-boost
Hmean     1     2692.19 (   0.00%)     2660.98 (  -1.16%)
Hmean     4     5218.93 (   0.00%)     5610.10 (   7.50%)
Hmean     7     7332.68 (   0.00%)     8378.24 (  14.26%)
Hmean     8     7462.03 (   0.00%)     8713.36 (  16.77%)
Stddev    1      231.85 (   0.00%)      257.49 ( -11.06%)
Stddev    4      681.11 (   0.00%)      312.64 (  54.10%)
Stddev    7     1072.07 (   0.00%)      730.29 (  31.88%)
Stddev    8     1472.77 (   0.00%)     1057.34 (  28.21%)

XFS
                            4.16.0                 4.16.0
                           vanilla              hwp-boost
Hmean     1     2675.02 (   0.00%)     2661.69 (  -0.50%)
Hmean     4     5049.45 (   0.00%)     5601.45 (  10.93%)
Hmean     7     7302.18 (   0.00%)     8348.16 (  14.32%)
Hmean     8     7596.83 (   0.00%)     8693.29 (  14.43%)
Stddev    1      225.41 (   0.00%)      246.74 (  -9.46%)
Stddev    4      761.33 (   0.00%)      334.77 (  56.03%)
Stddev    7     1093.93 (   0.00%)      811.30 (  25.84%)
Stddev    8     1465.06 (   0.00%)     1118.81 (  23.63%)

HACKBENCH
=========

NOTES: Varies the number of groups between 1 and NUMCPUS*4
MMTESTS CONFIG: global-dhp__scheduler-unbound
MEASURES: time (seconds)
LOWER is better

                             4.16.0                 4.16.0
                            vanilla              hwp-boost
Amean     1       0.8350 (   0.00%)      1.1577 ( -38.64%)
Amean     3       2.8367 (   0.00%)      3.7457 ( -32.04%)
Amean     5       6.7503 (   0.00%)      5.7977 (  14.11%)
Amean     7       7.8290 (   0.00%)      8.0343 (  -2.62%)
Amean     12     11.0560 (   0.00%)     11.9673 (  -8.24%)
Amean     18     15.2603 (   0.00%)     15.5247 (  -1.73%)
Amean     24     17.0283 (   0.00%)     17.9047 (  -5.15%)
Amean     30     19.9193 (   0.00%)     23.4670 ( -17.81%)
Amean     32     21.4637 (   0.00%)     23.4097 (  -9.07%)
Stddev    1       0.0636 (   0.00%)      0.0255 (  59.93%)
Stddev    3       0.1188 (   0.00%)      0.0235 (  80.22%)
Stddev    5       0.0755 (   0.00%)      0.1398 ( -85.13%)
Stddev    7       0.2778 (   0.00%)      0.1634 (  41.17%)
Stddev    12      0.5785 (   0.00%)      0.1030 (  82.19%)
Stddev    18      1.2099 (   0.00%)      0.7986 (  33.99%)
Stddev    24      0.2057 (   0.00%)      0.7030 (-241.72%)
Stddev    30      1.1303 (   0.00%)      0.7654 (  32.28%)
Stddev    32      0.2032 (   0.00%)      3.1626 (-1456.69%)

NAS PARALLEL BENCHMARK, C-CLASS (w/ openMP)
===========================================

NOTES: The various computational kernels are run separately; see
  https://www.nas.nasa.gov/publications/npb.html for the list of tasks (IS =
  Integer Sort, EP = Embarrassingly Parallel, etc)
MMTESTS CONFIG: global-dhp__nas-c-class-omp-full
MEASURES: time (seconds)
LOWER is better

                               4.16.0                 4.16.0
                              vanilla              hwp-boost
Amean     bt.C      169.82 (   0.00%)      170.54 (  -0.42%)
Stddev    bt.C        1.07 (   0.00%)        0.97 (   9.34%)
Amean     cg.C       41.81 (   0.00%)       42.08 (  -0.65%)
Stddev    cg.C        0.06 (   0.00%)        0.03 (  48.24%)
Amean     ep.C       26.63 (   0.00%)       26.47 (   0.61%)
Stddev    ep.C        0.37 (   0.00%)        0.24 (  35.35%)
Amean     ft.C       38.17 (   0.00%)       38.41 (  -0.64%)
Stddev    ft.C        0.33 (   0.00%)        0.32 (   3.78%)
Amean     is.C        1.49 (   0.00%)        1.40 (   6.02%)
Stddev    is.C        0.20 (   0.00%)        0.16 (  19.40%)
Amean     lu.C      217.46 (   0.00%)      220.21 (  -1.26%)
Stddev    lu.C        0.23 (   0.00%)        0.22 (   0.74%)
Amean     mg.C       18.56 (   0.00%)       18.80 (  -1.31%)
Stddev    mg.C        0.01 (   0.00%)        0.01 (  22.54%)
Amean     sp.C      293.25 (   0.00%)      296.73 (  -1.19%)
Stddev    sp.C        0.10 (   0.00%)        0.06 (  42.67%)
Amean     ua.C      170.74 (   0.00%)      172.02 (  -0.75%)
Stddev    ua.C        0.28 (   0.00%)        0.31 ( -12.89%)

HOW TO REPRODUCE
================

To install MMTests, clone the git repo at
https://github.com/gormanm/mmtests.git

To run a config (ie a set of benchmarks, such as
config-global-dhp__nas-c-class-omp-full), use the command
./run-mmtests.sh --config configs/$CONFIG $MNEMONIC-NAME
from the top-level directory; the benchmark source will be downloaded from its
canonical internet location, compiled and run.

To compare results from two runs, use
./bin/compare-mmtests.pl --directory ./work/log \
                         --benchmark $BENCHMARK-NAME \
                         --names $MNEMONIC-NAME-1,$MNEMONIC-NAME-2
from the top-level directory.

==================
From RFC Series:
v3
- Removed atomic bit operation as suggested.
- Added description of contention with user space.
- Removed hwp cache, boost utililty function patch and merged with util callback
  patch. This way any value set is used somewhere.

Waiting for test results from Mel Gorman, who is the original reporter.

v2
This is a much simpler version than the previous one and only consider IO
boost, using the existing mechanism. There is no change in this series
beyond intel_pstate driver.

Once PeterZ finishes his work on frequency invariant, I will revisit
thread migration optimization in HWP mode.

Other changes:
- Gradual boost instead of single step as suggested by PeterZ.
- Cross CPU synchronization concerns identified by Rafael.
- Split the patch for HWP MSR value caching as suggested by PeterZ.

Not changed as suggested:
There is no architecture way to identify platform with Per-core
P-states, so still have to enable feature based on CPU model.

-----------
v1

This series tries to address some concern in performance particularly with IO
workloads (Reported by Mel Gorman), when HWP is using intel_pstate powersave
policy.

Background
HWP performance can be controlled by user space using sysfs interface for
max/min frequency limits and energy performance preference settings. Based on
workload characteristics these can be adjusted from user space. These limits
are not changed dynamically by kernel based on workload.

By default HWP defaults to energy performance preference value of 0x80 on
majority of platforms(Scale is 0-255, 0 is max performance and 255 is min).
This value offers best performance/watt and for majority of server workloads
performance doesn't suffer. Also users always have option to use performance
policy of intel_pstate, to get best performance. But user tend to run with
out of box configuration, which is powersave policy on most of the distros.

In some case it is possible to dynamically adjust performance, for example,
when a CPU is woken up due to IO completion or thread migrate to a new CPU. In
this case HWP algorithm will take some time to build utilization and ramp up
P-states. So this may results in lower performance for some IO workloads and
workloads which tend to migrate. The idea of this patch series is to
temporarily boost performance dynamically in these cases. This is only
applicable only when user is using powersave policy, not in performance policy.

Results on a Skylake server:

Benchmark                       Improvement %
----------------------------------------------------------------------
dbench                          50.36
thread IO bench (tiobench)      10.35
File IO                         9.81
sqlite                          15.76
X264 -104 cores                 9.75

Spec Power                      (Negligible impact 7382 Vs. 7378)
Idle Power                      No change observed
-----------------------------------------------------------------------

HWP brings in best performace/watt at EPP=0x80. Since we are boosting
EPP here to 0, the performance/watt drops upto 10%. So there is a power
penalty of these changes.

Also Mel Gorman provided test results on a prior patchset, which shows
benifits of this series.

Srinivas Pandruvada (4):
  cpufreq: intel_pstate: Add HWP boost utility and sched util hooks
  cpufreq: intel_pstate: HWP boost performance on IO wakeup
  cpufreq: intel_pstate: New sysfs entry to control HWP boost
  cpufreq: intel_pstate: enable boost for Skylake Xeon

 drivers/cpufreq/intel_pstate.c | 179 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 176 insertions(+), 3 deletions(-)

-- 
2.13.6