linux-toradex.git/kernel/sched/features.h, branch v5.3-rc6

sched/fair: Replace source_load() & target_load() with weighted_cpuload()

2019-06-03T09:49:39+00:00

With LB_BIAS disabled, source_load() & target_load() return
weighted_cpuload(). Replace both with calls to weighted_cpuload().

The function to obtain the load index (sd->*_idx) for an sd,
get_sd_load_idx(), can be removed as well.

Finally, get rid of the sched feature LB_BIAS.

Signed-off-by: Dietmar Eggemann 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Rik van Riel 
Cc: Frederic Weisbecker 
Cc: Linus Torvalds 
Cc: Morten Rasmussen 
Cc: Patrick Bellasi 
Cc: Peter Zijlstra 
Cc: Quentin Perret 
Cc: Thomas Gleixner 
Cc: Valentin Schneider 
Cc: Vincent Guittot 
Link: https://lkml.kernel.org/r/20190527062116.11512-3-dietmar.eggemann@arm.com
Signed-off-by: Ingo Molnar

sched/fair: Disable LB_BIAS by default

2018-10-02T07:45:01+00:00

LB_BIAS allows the adjustment on how conservative load should be
balanced.

The rq->cpu_load[idx] array is used for this functionality. It contains
weighted CPU load decayed average values over different intervals
(idx = 1..4). Idx = 0 is the weighted CPU load itself.

The values are updated during scheduler_tick, before idle balance and at
nohz exit.

There are 5 different types of idx's per sched domain (sd). Each of them
is used to index into the rq->cpu_load[idx] array in a specific scenario
(busy, idle and newidle for load balancing, forkexec for wake-up
slow-path load balancing and wake for affine wakeup based on weight).
Only the sd idx's for busy and idle load balancing are set to 2,3 or 1,2
respectively. All the other sd idx's are set to 0.

Conservative load balancing is achieved for sd idx's >= 1 by using the
min/max (source_load()/target_load()) value between the current weighted
CPU load and the rq->cpu_load[sd idx -1] for the busiest(idlest)/local
CPU load in load balancing or vice versa in the wake-up slow-path load
balancing.
There is no conservative balancing for sd idx = 0 since only current
weighted CPU load is used in this case.

It is very likely that LB_BIAS' influence on load balancing can be
neglected (see test results below). This is further supported by:

(1) Weighted CPU load today is by itself a decayed average value (PELT)
    (cfs_rq->avg->runnable_load_avg) and not the instantaneous load
    (rq->load.weight) it was when LB_BIAS was introduced.

(2) Sd imbalance_pct is used for CPU_NEWLY_IDLE and CPU_NOT_IDLE (relate
    to sd's newidle and busy idx) in find_busiest_group() when comparing
    busiest and local avg load to make load balancing even more
    conservative.

(3) The sd forkexec and newidle idx are always set to 0 so there is no
    adjustment on how conservatively load balancing is done here.

(4) Affine wakeup based on weight (wake_affine_weight()) will not be
    impacted since the sd wake idx is always set to 0.

Let's disable LB_BIAS by default for a few kernel releases to make sure
that no workload and no scheduler topology is affected. The benefit of
being able to remove the LB_BIAS dependency from source_load() and
target_load() is that the entire rq->cpu_load[idx] code could be removed
in this case.

It is really hard to say if there is no regression w/o testing this with
a lot of different workloads on a lot of different platforms, especially
NUMA machines.
The following 104 LKP (Linux Kernel Performance) tests were run by the
0-Day guys mostly on multi-socket hosts with a larger number of logical
cpus (88, 192).
The base for the test was commit b3dae109fa89 ("sched/swait: Rename to
exclusive") (tip/sched/core v4.18-rc1).
Only 2 out of the 104 tests had a significant change in one of the
metrics (fsmark/1x-1t-1HDD-btrfs-nfsv4-4M-60G-NoSync-performance +7%
files_per_sec, unixbench/300s-100%-syscall-performance -11% score).
Tests which showed a change in one of the metrics are marked with a '*'
and this change is listed as well.

(a) lkp-bdw-ep3:
      88 threads Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz 64G

    dd-write/10m-1HDD-cfq-btrfs-100dd-performance
    fsmark/1x-1t-1HDD-xfs-nfsv4-4M-60G-NoSync-performance
  * fsmark/1x-1t-1HDD-btrfs-nfsv4-4M-60G-NoSync-performance
      7.50  7%  8.00  ±  6%  fsmark.files_per_sec
    fsmark/1x-1t-1HDD-btrfs-nfsv4-4M-60G-fsyncBeforeClose-performance
    fsmark/1x-1t-1HDD-btrfs-4M-60G-NoSync-performance
    fsmark/1x-1t-1HDD-btrfs-4M-60G-fsyncBeforeClose-performance
    kbuild/300s-50%-vmlinux_prereq-performance
    kbuild/300s-200%-vmlinux_prereq-performance
    kbuild/300s-50%-vmlinux_prereq-performance-1HDD-ext4
    kbuild/300s-200%-vmlinux_prereq-performance-1HDD-ext4

(b) lkp-skl-4sp1:
      192 threads Intel(R) Xeon(R) Platinum 8160 768G

    dbench/100%-performance
    ebizzy/200%-100x-10s-performance
    hackbench/1600%-process-pipe-performance
    iperf/300s-cs-localhost-tcp-performance
    iperf/300s-cs-localhost-udp-performance
    perf-bench-numa-mem/2t-300M-performance
    perf-bench-sched-pipe/10000000ops-process-performance
    perf-bench-sched-pipe/10000000ops-threads-performance
    schbench/2-16-300-30000-30000-performance
    tbench/100%-cs-localhost-performance

(c) lkp-bdw-ep6:
      88 threads Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz 128G

    stress-ng/100%-60s-pipe-performance
    unixbench/300s-1-whetstone-double-performance
    unixbench/300s-1-shell1-performance
    unixbench/300s-1-shell8-performance
    unixbench/300s-1-pipe-performance
  * unixbench/300s-1-context1-performance
      312  315  unixbench.score
    unixbench/300s-1-spawn-performance
    unixbench/300s-1-syscall-performance
    unixbench/300s-1-dhry2reg-performance
    unixbench/300s-1-fstime-performance
    unixbench/300s-1-fsbuffer-performance
    unixbench/300s-1-fsdisk-performance
    unixbench/300s-100%-whetstone-double-performance
    unixbench/300s-100%-shell1-performance
    unixbench/300s-100%-shell8-performance
    unixbench/300s-100%-pipe-performance
    unixbench/300s-100%-context1-performance
    unixbench/300s-100%-spawn-performance
  * unixbench/300s-100%-syscall-performance
      3571  ±  3%  -11%  3183  ±  4%  unixbench.score
    unixbench/300s-100%-dhry2reg-performance
    unixbench/300s-100%-fstime-performance
    unixbench/300s-100%-fsbuffer-performance
    unixbench/300s-100%-fsdisk-performance
    unixbench/300s-1-execl-performance
    unixbench/300s-100%-execl-performance
  * will-it-scale/brk1-performance
      365004  360387  will-it-scale.per_thread_ops
  * will-it-scale/dup1-performance
      432401  437596  will-it-scale.per_thread_ops
    will-it-scale/eventfd1-performance
    will-it-scale/futex1-performance
    will-it-scale/futex2-performance
    will-it-scale/futex3-performance
    will-it-scale/futex4-performance
    will-it-scale/getppid1-performance
    will-it-scale/lock1-performance
    will-it-scale/lseek1-performance
    will-it-scale/lseek2-performance
  * will-it-scale/malloc1-performance
      47025  45817  will-it-scale.per_thread_ops
      77499  76529  will-it-scale.per_process_ops
    will-it-scale/malloc2-performance
  * will-it-scale/mmap1-performance
      123399  120815  will-it-scale.per_thread_ops
      152219  149833  will-it-scale.per_process_ops
  * will-it-scale/mmap2-performance
      107327  104714  will-it-scale.per_thread_ops
      136405  133765  will-it-scale.per_process_ops
    will-it-scale/open1-performance
  * will-it-scale/open2-performance
      171570  168805  will-it-scale.per_thread_ops
      532644  526202  will-it-scale.per_process_ops
    will-it-scale/page_fault1-performance
    will-it-scale/page_fault2-performance
    will-it-scale/page_fault3-performance
    will-it-scale/pipe1-performance
    will-it-scale/poll1-performance
  * will-it-scale/poll2-performance
      176134  172848  will-it-scale.per_thread_ops
      281361  275053  will-it-scale.per_process_ops
    will-it-scale/posix_semaphore1-performance
    will-it-scale/pread1-performance
    will-it-scale/pread2-performance
    will-it-scale/pread3-performance
    will-it-scale/pthread_mutex1-performance
    will-it-scale/pthread_mutex2-performance
    will-it-scale/pwrite1-performance
    will-it-scale/pwrite2-performance
    will-it-scale/pwrite3-performance
  * will-it-scale/read1-performance
      1190563  1174833  will-it-scale.per_thread_ops
  * will-it-scale/read2-performance
      1105369  1080427  will-it-scale.per_thread_ops
    will-it-scale/readseek1-performance
  * will-it-scale/readseek2-performance
      261818  259040  will-it-scale.per_thread_ops
    will-it-scale/readseek3-performance
  * will-it-scale/sched_yield-performance
      2408059  2382034  will-it-scale.per_thread_ops
    will-it-scale/signal1-performance
    will-it-scale/unix1-performance
    will-it-scale/unlink1-performance
    will-it-scale/unlink2-performance
  * will-it-scale/write1-performance
      976701  961588  will-it-scale.per_thread_ops
  * will-it-scale/writeseek1-performance
      831898  822448  will-it-scale.per_thread_ops
  * will-it-scale/writeseek2-performance
      228248  225065  will-it-scale.per_thread_ops
  * will-it-scale/writeseek3-performance
      226670  224058  will-it-scale.per_thread_ops
    will-it-scale/context_switch1-performance
    aim7/performance-fork_test-2000
  * aim7/performance-brk_test-3000
      74869  76676  aim7.jobs-per-min
    aim7/performance-disk_cp-3000
    aim7/performance-disk_rd-3000
    aim7/performance-sieve-3000
    aim7/performance-page_test-3000
    aim7/performance-creat-clo-3000
    aim7/performance-mem_rtns_1-8000
    aim7/performance-disk_wrt-8000
    aim7/performance-pipe_cpy-8000
    aim7/performance-ram_copy-8000

(d) lkp-avoton3:
      8 threads Intel(R) Atom(TM) CPU C2750 @ 2.40GHz 16G

    netperf/ipv4-900s-200%-cs-localhost-TCP_STREAM-performance

Signed-off-by: Dietmar Eggemann 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Fengguang Wu 
Cc: Li Zhijian 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/20180809135753.21077-1-dietmar.eggemann@arm.com
Signed-off-by: Ingo Molnar

sched/fair: Update util_est only on util_avg updates

2018-03-20T07:11:09+00:00

The estimated utilization of a task is currently updated every time the
task is dequeued. However, to keep overheads under control, PELT signals
are effectively updated at maximum once every 1ms.

Thus, for really short running tasks, it can happen that their util_avg
value has not been updates since their last enqueue.  If such tasks are
also frequently running tasks (e.g. the kind of workload generated by
hackbench) it can also happen that their util_avg is updated only every
few activations.

This means that updating util_est at every dequeue potentially introduces
not necessary overheads and it's also conceptually wrong if the util_avg
signal has never been updated during a task activation.

Let's introduce a throttling mechanism on task's util_est updates
to sync them with util_avg updates. To make the solution memory
efficient, both in terms of space and load/store operations, we encode a
synchronization flag into the LSB of util_est.enqueued.
This makes util_est an even values only metric, which is still
considered good enough for its purpose.
The synchronization bit is (re)set by __update_load_avg_se() once the
PELT signal of a task has been updated during its last activation.

Such a throttling mechanism allows to keep under control util_est
overheads in the wakeup hot path, thus making it a suitable mechanism
which can be enabled also on high-intensity workload systems.
Thus, this now switches on by default the estimation utilization
scheduler feature.

Suggested-by: Chris Redpath 
Signed-off-by: Patrick Bellasi 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Dietmar Eggemann 
Cc: Joel Fernandes 
Cc: Juri Lelli 
Cc: Linus Torvalds 
Cc: Morten Rasmussen 
Cc: Paul Turner 
Cc: Peter Zijlstra 
Cc: Rafael J . Wysocki 
Cc: Steve Muckle 
Cc: Thomas Gleixner 
Cc: Todd Kjos 
Cc: Vincent Guittot 
Cc: Viresh Kumar 
Link: http://lkml.kernel.org/r/20180309095245.11071-5-patrick.bellasi@arm.com
Signed-off-by: Ingo Molnar

sched/fair: Add util_est on top of PELT

2018-03-20T07:11:06+00:00

The util_avg signal computed by PELT is too variable for some use-cases.
For example, a big task waking up after a long sleep period will have its
utilization almost completely decayed. This introduces some latency before
schedutil will be able to pick the best frequency to run a task.

The same issue can affect task placement. Indeed, since the task
utilization is already decayed at wakeup, when the task is enqueued in a
CPU, this can result in a CPU running a big task as being temporarily
represented as being almost empty. This leads to a race condition where
other tasks can be potentially allocated on a CPU which just started to run
a big task which slept for a relatively long period.

Moreover, the PELT utilization of a task can be updated every [ms], thus
making it a continuously changing value for certain longer running
tasks. This means that the instantaneous PELT utilization of a RUNNING
task is not really meaningful to properly support scheduler decisions.

For all these reasons, a more stable signal can do a better job of
representing the expected/estimated utilization of a task/cfs_rq.
Such a signal can be easily created on top of PELT by still using it as
an estimator which produces values to be aggregated on meaningful
events.

This patch adds a simple implementation of util_est, a new signal built on
top of PELT's util_avg where:

    util_est(task) = max(task::util_avg, f(task::util_avg@dequeue))

This allows to remember how big a task has been reported by PELT in its
previous activations via f(task::util_avg@dequeue), which is the new
_task_util_est(struct task_struct*) function added by this patch.

If a task should change its behavior and it runs longer in a new
activation, after a certain time its util_est will just track the
original PELT signal (i.e. task::util_avg).

The estimated utilization of cfs_rq is defined only for root ones.
That's because the only sensible consumer of this signal are the
scheduler and schedutil when looking for the overall CPU utilization
due to FAIR tasks.

For this reason, the estimated utilization of a root cfs_rq is simply
defined as:

    util_est(cfs_rq) = max(cfs_rq::util_avg, cfs_rq::util_est::enqueued)

where:

    cfs_rq::util_est::enqueued = sum(_task_util_est(task))
                                 for each RUNNABLE task on that root cfs_rq

It's worth noting that the estimated utilization is tracked only for
objects of interests, specifically:

 - Tasks: to better support tasks placement decisions
 - root cfs_rqs: to better support both tasks placement decisions as
                 well as frequencies selection

Signed-off-by: Patrick Bellasi 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Dietmar Eggemann 
Cc: Joel Fernandes 
Cc: Juri Lelli 
Cc: Linus Torvalds 
Cc: Morten Rasmussen 
Cc: Paul Turner 
Cc: Rafael J . Wysocki 
Cc: Steve Muckle 
Cc: Thomas Gleixner 
Cc: Todd Kjos 
Cc: Vincent Guittot 
Cc: Viresh Kumar 
Link: http://lkml.kernel.org/r/20180309095245.11071-2-patrick.bellasi@arm.com
Signed-off-by: Ingo Molnar

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

2017-11-02T10:10:55+00:00

Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier.  The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
 - file had no licensing information it it.
 - file was a */uapi/* one with no licensing information in it,
 - file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne.  Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed.  Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
 - Files considered eligible had to be source code files.
 - Make and config files were included as candidates if they contained >5
   lines of source
 - File already had some variant of a license header in it (even if <5
   lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

 - when both scanners couldn't find any license traces, file was
   considered to have no license information in it, and the top level
   COPYING file license applied.

   For non */uapi/* files that summary was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0                                              11139

   and resulted in the first patch in this series.

   If that file was a */uapi/* path one, it was "GPL-2.0 WITH
   Linux-syscall-note" otherwise it was "GPL-2.0".  Results of that was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0 WITH Linux-syscall-note                        930

   and resulted in the second patch in this series.

 - if a file had some form of licensing information in it, and was one
   of the */uapi/* ones, it was denoted with the Linux-syscall-note if
   any GPL family license was found in the file or had no licensing in
   it (per prior point).  Results summary:

   SPDX license identifier                            # files
   ---------------------------------------------------|------
   GPL-2.0 WITH Linux-syscall-note                       270
   GPL-2.0+ WITH Linux-syscall-note                      169
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause)    21
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)    17
   LGPL-2.1+ WITH Linux-syscall-note                      15
   GPL-1.0+ WITH Linux-syscall-note                       14
   ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause)    5
   LGPL-2.0+ WITH Linux-syscall-note                       4
   LGPL-2.1 WITH Linux-syscall-note                        3
   ((GPL-2.0 WITH Linux-syscall-note) OR MIT)              3
   ((GPL-2.0 WITH Linux-syscall-note) AND MIT)             1

   and that resulted in the third patch in this series.

 - when the two scanners agreed on the detected license(s), that became
   the concluded license(s).

 - when there was disagreement between the two scanners (one detected a
   license but the other didn't, or they both detected different
   licenses) a manual inspection of the file occurred.

 - In most cases a manual inspection of the information in the file
   resulted in a clear resolution of the license that should apply (and
   which scanner probably needed to revisit its heuristics).

 - When it was not immediately clear, the license identifier was
   confirmed with lawyers working with the Linux Foundation.

 - If there was any question as to the appropriate license identifier,
   the file was flagged for further research and to be revisited later
   in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights.  The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
 - a full scancode scan run, collecting the matched texts, detected
   license ids and scores
 - reviewing anything where there was a license detected (about 500+
   files) to ensure that the applied SPDX license was correct
 - reviewing anything where there was no detection but the patch license
   was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
   SPDX license was correct

This produced a worksheet with 20 files needing minor correction.  This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg.  Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected.  This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.)  Finally Greg ran the script using the .csv files to
generate the patches.

Reviewed-by: Kate Stewart 
Reviewed-by: Philippe Ombredanne 
Reviewed-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

sched/core: Address more wake_affine() regressions

2017-10-10T08:14:03+00:00

The trivial wake_affine_idle() implementation is very good for a
number of workloads, but it comes apart at the moment there are no
idle CPUs left, IOW. the overloaded case.

hackbench:

		NO_WA_WEIGHT		WA_WEIGHT

hackbench-20  : 7.362717561 seconds	6.450509391 seconds

(win)

netperf:

		  NO_WA_WEIGHT		WA_WEIGHT

TCP_SENDFILE-1	: Avg: 54524.6		Avg: 52224.3
TCP_SENDFILE-10	: Avg: 48185.2          Avg: 46504.3
TCP_SENDFILE-20	: Avg: 29031.2          Avg: 28610.3
TCP_SENDFILE-40	: Avg: 9819.72          Avg: 9253.12
TCP_SENDFILE-80	: Avg: 5355.3           Avg: 4687.4

TCP_STREAM-1	: Avg: 41448.3          Avg: 42254
TCP_STREAM-10	: Avg: 24123.2          Avg: 25847.9
TCP_STREAM-20	: Avg: 15834.5          Avg: 18374.4
TCP_STREAM-40	: Avg: 5583.91          Avg: 5599.57
TCP_STREAM-80	: Avg: 2329.66          Avg: 2726.41

TCP_RR-1	: Avg: 80473.5          Avg: 82638.8
TCP_RR-10	: Avg: 72660.5          Avg: 73265.1
TCP_RR-20	: Avg: 52607.1          Avg: 52634.5
TCP_RR-40	: Avg: 57199.2          Avg: 56302.3
TCP_RR-80	: Avg: 25330.3          Avg: 26867.9

UDP_RR-1	: Avg: 108266           Avg: 107844
UDP_RR-10	: Avg: 95480            Avg: 95245.2
UDP_RR-20	: Avg: 68770.8          Avg: 68673.7
UDP_RR-40	: Avg: 76231            Avg: 75419.1
UDP_RR-80	: Avg: 34578.3          Avg: 35639.1

UDP_STREAM-1	: Avg: 64684.3          Avg: 66606
UDP_STREAM-10	: Avg: 52701.2          Avg: 52959.5
UDP_STREAM-20	: Avg: 30376.4          Avg: 29704
UDP_STREAM-40	: Avg: 15685.8          Avg: 15266.5
UDP_STREAM-80	: Avg: 8415.13          Avg: 7388.97

(wins and losses)

sysbench:

		    NO_WA_WEIGHT		WA_WEIGHT

sysbench-mysql-2  :  2135.17 per sec.		 2142.51 per sec.
sysbench-mysql-5  :  4809.68 per sec.            4800.19 per sec.
sysbench-mysql-10 :  9158.59 per sec.            9157.05 per sec.
sysbench-mysql-20 : 14570.70 per sec.           14543.55 per sec.
sysbench-mysql-40 : 22130.56 per sec.           22184.82 per sec.
sysbench-mysql-80 : 20995.56 per sec.           21904.18 per sec.

sysbench-psql-2   :  1679.58 per sec.            1705.06 per sec.
sysbench-psql-5   :  3797.69 per sec.            3879.93 per sec.
sysbench-psql-10  :  7253.22 per sec.            7258.06 per sec.
sysbench-psql-20  : 11166.75 per sec.           11220.00 per sec.
sysbench-psql-40  : 17277.28 per sec.           17359.78 per sec.
sysbench-psql-80  : 17112.44 per sec.           17221.16 per sec.

(increase on the top end)

tbench:

NO_WA_WEIGHT

Throughput 685.211 MB/sec   2 clients   2 procs  max_latency=0.123 ms
Throughput 1596.64 MB/sec   5 clients   5 procs  max_latency=0.119 ms
Throughput 2985.47 MB/sec  10 clients  10 procs  max_latency=0.262 ms
Throughput 4521.15 MB/sec  20 clients  20 procs  max_latency=0.506 ms
Throughput 9438.1  MB/sec  40 clients  40 procs  max_latency=2.052 ms
Throughput 8210.5  MB/sec  80 clients  80 procs  max_latency=8.310 ms

WA_WEIGHT

Throughput 697.292 MB/sec   2 clients   2 procs  max_latency=0.127 ms
Throughput 1596.48 MB/sec   5 clients   5 procs  max_latency=0.080 ms
Throughput 2975.22 MB/sec  10 clients  10 procs  max_latency=0.254 ms
Throughput 4575.14 MB/sec  20 clients  20 procs  max_latency=0.502 ms
Throughput 9468.65 MB/sec  40 clients  40 procs  max_latency=2.069 ms
Throughput 8631.73 MB/sec  80 clients  80 procs  max_latency=8.605 ms

(increase on the top end)

Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Rik van Riel 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

sched/core: Fix wake_affine() performance regression

2017-10-10T08:14:02+00:00

Eric reported a sysbench regression against commit:

  3fed382b46ba ("sched/numa: Implement NUMA node level wake_affine()")

Similarly, Rik was looking at the NAS-lu.C benchmark, which regressed
against his v3.10 enterprise kernel.

PRE (current tip/master):

 ivb-ep sysbench:

   2: [30 secs]     transactions:                        64110  (2136.94 per sec.)
   5: [30 secs]     transactions:                        143644 (4787.99 per sec.)
  10: [30 secs]     transactions:                        274298 (9142.93 per sec.)
  20: [30 secs]     transactions:                        418683 (13955.45 per sec.)
  40: [30 secs]     transactions:                        320731 (10690.15 per sec.)
  80: [30 secs]     transactions:                        355096 (11834.28 per sec.)

 hsw-ex NAS:

 OMP_PROC_BIND/lu.C.x_threads_144_run_1.log: Time in seconds =                    18.01
 OMP_PROC_BIND/lu.C.x_threads_144_run_2.log: Time in seconds =                    17.89
 OMP_PROC_BIND/lu.C.x_threads_144_run_3.log: Time in seconds =                    17.93
 lu.C.x_threads_144_run_1.log: Time in seconds =                   434.68
 lu.C.x_threads_144_run_2.log: Time in seconds =                   405.36
 lu.C.x_threads_144_run_3.log: Time in seconds =                   433.83

POST (+patch):

 ivb-ep sysbench:

   2: [30 secs]     transactions:                        64494  (2149.75 per sec.)
   5: [30 secs]     transactions:                        145114 (4836.99 per sec.)
  10: [30 secs]     transactions:                        278311 (9276.69 per sec.)
  20: [30 secs]     transactions:                        437169 (14571.60 per sec.)
  40: [30 secs]     transactions:                        669837 (22326.73 per sec.)
  80: [30 secs]     transactions:                        631739 (21055.88 per sec.)

 hsw-ex NAS:

 lu.C.x_threads_144_run_1.log: Time in seconds =                    23.36
 lu.C.x_threads_144_run_2.log: Time in seconds =                    22.96
 lu.C.x_threads_144_run_3.log: Time in seconds =                    22.52

This patch takes out all the shiny wake_affine() stuff and goes back to
utter basics. Between the two CPUs involved with the wakeup (the CPU
doing the wakeup and the CPU we ran on previously) pick the CPU we can
run on _now_.

This restores much of the regressions against the older kernels,
but leaves some ground in the overloaded case. The default-enabled
WA_WEIGHT (which will be introduced in the next patch) is an attempt
to address the overloaded situation.

Reported-by: Eric Farman 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Christian Borntraeger 
Cc: Linus Torvalds 
Cc: Matthew Rosato 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Rik van Riel 
Cc: Thomas Gleixner 
Cc: jinpuwang@gmail.com
Cc: vcaputo@pengaru.com
Fixes: 3fed382b46ba ("sched/numa: Implement NUMA node level wake_affine()")
Signed-off-by: Ingo Molnar

sched/core: Implement new approach to scale select_idle_cpu()

2017-06-08T08:25:17+00:00

Hackbench recently suffered a bunch of pain, first by commit:

  4c77b18cf8b7 ("sched/fair: Make select_idle_cpu() more aggressive")

and then by commit:

  c743f0a5c50f ("sched/fair, cpumask: Export for_each_cpu_wrap()")

which fixed a bug in the initial for_each_cpu_wrap() implementation
that made select_idle_cpu() even more expensive. The bug was that it
would skip over CPUs when bits were consequtive in the bitmask.

This however gave me an idea to fix select_idle_cpu(); where the old
scheme was a cliff-edge throttle on idle scanning, this introduces a
more gradual approach. Instead of stopping to scan entirely, we limit
how many CPUs we scan.

Initial benchmarks show that it mostly recovers hackbench while not
hurting anything else, except Mason's schbench, but not as bad as the
old thing.

It also appears to recover the tbench high-end, which also suffered like
hackbench.

Tested-by: Matt Fleming 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Chris Mason 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: hpa@zytor.com
Cc: kitsunyan 
Cc: linux-kernel@vger.kernel.org
Cc: lvenanci@redhat.com
Cc: riel@redhat.com
Cc: xiaolong.ye@intel.com
Link: http://lkml.kernel.org/r/20170517105350.hk5m4h4jb6dfr65a@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar

sched/topology: Remove FORCE_SD_OVERLAP

2017-05-15T08:15:28+00:00

Its an obsolete debug mechanism and future code wants to rely on
properties this undermines.

Namely, it would be good to assume that SD_OVERLAP domains have
children, but if we build the entire hierarchy with SD_OVERLAP this is
obviously false.

Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

sched/core: Add WARNING for multiple update_rq_clock() calls

2017-03-16T08:46:21+00:00

Now that we have no missing calls, add a warning to find multiple
calls.

By having only a single update_rq_clock() call per rq-lock section,
the section appears 'atomic' wrt time.

Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Signed-off-by: Ingo Molnar