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  1. 25 Feb, 2016 5 commits
    • Paul Gortmaker's avatar
      rcu: Use simple wait queues where possible in rcutree · abedf8e2
      Paul Gortmaker authored 
      As of commit dae6e64d ("rcu: Introduce proper blocking to no-CBs kthreads
GP waits") the RCU subsystem started making use of wait queues.

Here we convert all additions of RCU wait queues to use simple wait queues,
since they don't need the extra overhead of the full wait queue features.

Originally this was done for RT kernels[1], since we would get things like...

  BUG: sleeping function called from invalid context at kernel/rtmutex.c:659
  in_atomic(): 1, irqs_disabled(): 1, pid: 8, name: rcu_preempt
  Pid: 8, comm: rcu_preempt Not tainted
  Call Trace:
   [<ffffffff8106c8d0>] __might_sleep+0xd0/0xf0
   [<ffffffff817d77b4>] rt_spin_lock+0x24/0x50
   [<ffffffff8106fcf6>] __wake_up+0x36/0x70
   [<ffffffff810c4542>] rcu_gp_kthread+0x4d2/0x680
   [<ffffffff8105f910>] ? __init_waitqueue_head+0x50/0x50
   [<ffffffff810c4070>] ? rcu_gp_fqs+0x80/0x80
   [<ffffffff8105eabb>] kthread+0xdb/0xe0
   [<ffffffff8106b912>] ? finish_task_switch+0x52/0x100
   [<ffffffff817e0754>] kernel_thread_helper+0x4/0x10
   [<ffffffff8105e9e0>] ? __init_kthread_worker+0x60/0x60
   [<ffffffff817e0750>] ? gs_change+0xb/0xb

...and hence simple wait queues were deployed on RT out of necessity
(as simple wait uses a raw lock), but mainline might as well take
advantage of the more streamline support as well.

[1] This is a carry forward of work from v3.10-rt; the original conversion
was by Thomas on an earlier -rt version, and Sebastian extended it to
additional post-3.10 added RCU waiters; here I've added a commit log and
unified the RCU changes into one, and uprev'd it to match mainline RCU.
Signed-off-by: default avatarDaniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-rt-users@vger.kernel.org
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1455871601-27484-6-git-send-email-wagi@monom.orgSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      abedf8e2
    • Daniel Wagner's avatar
      rcu: Do not call rcu_nocb_gp_cleanup() while holding rnp->lock · 065bb78c
      Daniel Wagner authored 
      rcu_nocb_gp_cleanup() is called while holding rnp->lock. Currently,
this is okay because the wake_up_all() in rcu_nocb_gp_cleanup() will
not enable the IRQs. lockdep is happy.

By switching over using swait this is not true anymore. swake_up_all()
enables the IRQs while processing the waiters. __do_softirq() can now
run and will eventually call rcu_process_callbacks() which wants to
grap nrp->lock.

Let's move the rcu_nocb_gp_cleanup() call outside the lock before we
switch over to swait.

If we would hold the rnp->lock and use swait, lockdep reports
following:

 =================================
 [ INFO: inconsistent lock state ]
 4.2.0-rc5-00025-g9a73ba0 #136 Not tainted
 ---------------------------------
 inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
 rcu_preempt/8 [HC0[0]:SC0[0]:HE1:SE1] takes:
  (rcu_node_1){+.?...}, at: [<ffffffff811387c7>] rcu_gp_kthread+0xb97/0xeb0
 {IN-SOFTIRQ-W} state was registered at:
   [<ffffffff81109b9f>] __lock_acquire+0xd5f/0x21e0
   [<ffffffff8110be0f>] lock_acquire+0xdf/0x2b0
   [<ffffffff81841cc9>] _raw_spin_lock_irqsave+0x59/0xa0
   [<ffffffff81136991>] rcu_process_callbacks+0x141/0x3c0
   [<ffffffff810b1a9d>] __do_softirq+0x14d/0x670
   [<ffffffff810b2214>] irq_exit+0x104/0x110
   [<ffffffff81844e96>] smp_apic_timer_interrupt+0x46/0x60
   [<ffffffff81842e70>] apic_timer_interrupt+0x70/0x80
   [<ffffffff810dba66>] rq_attach_root+0xa6/0x100
   [<ffffffff810dbc2d>] cpu_attach_domain+0x16d/0x650
   [<ffffffff810e4b42>] build_sched_domains+0x942/0xb00
   [<ffffffff821777c2>] sched_init_smp+0x509/0x5c1
   [<ffffffff821551e3>] kernel_init_freeable+0x172/0x28f
   [<ffffffff8182cdce>] kernel_init+0xe/0xe0
   [<ffffffff8184231f>] ret_from_fork+0x3f/0x70
 irq event stamp: 76
 hardirqs last  enabled at (75): [<ffffffff81841330>] _raw_spin_unlock_irq+0x30/0x60
 hardirqs last disabled at (76): [<ffffffff8184116f>] _raw_spin_lock_irq+0x1f/0x90
 softirqs last  enabled at (0): [<ffffffff810a8df2>] copy_process.part.26+0x602/0x1cf0
 softirqs last disabled at (0): [<          (null)>]           (null)
 other info that might help us debug this:
  Possible unsafe locking scenario:
        CPU0
        ----
   lock(rcu_node_1);
   <Interrupt>
     lock(rcu_node_1);
  *** DEADLOCK ***
 1 lock held by rcu_preempt/8:
  #0:  (rcu_node_1){+.?...}, at: [<ffffffff811387c7>] rcu_gp_kthread+0xb97/0xeb0
 stack backtrace:
 CPU: 0 PID: 8 Comm: rcu_preempt Not tainted 4.2.0-rc5-00025-g9a73ba0 #136
 Hardware name: Dell Inc. PowerEdge R820/066N7P, BIOS 2.0.20 01/16/2014
  0000000000000000 000000006d7e67d8 ffff881fb081fbd8 ffffffff818379e0
  0000000000000000 ffff881fb0812a00 ffff881fb081fc38 ffffffff8110813b
  0000000000000000 0000000000000001 ffff881f00000001 ffffffff8102fa4f
 Call Trace:
  [<ffffffff818379e0>] dump_stack+0x4f/0x7b
  [<ffffffff8110813b>] print_usage_bug+0x1db/0x1e0
  [<ffffffff8102fa4f>] ? save_stack_trace+0x2f/0x50
  [<ffffffff811087ad>] mark_lock+0x66d/0x6e0
  [<ffffffff81107790>] ? check_usage_forwards+0x150/0x150
  [<ffffffff81108898>] mark_held_locks+0x78/0xa0
  [<ffffffff81841330>] ? _raw_spin_unlock_irq+0x30/0x60
  [<ffffffff81108a28>] trace_hardirqs_on_caller+0x168/0x220
  [<ffffffff81108aed>] trace_hardirqs_on+0xd/0x10
  [<ffffffff81841330>] _raw_spin_unlock_irq+0x30/0x60
  [<ffffffff810fd1c7>] swake_up_all+0xb7/0xe0
  [<ffffffff811386e1>] rcu_gp_kthread+0xab1/0xeb0
  [<ffffffff811089bf>] ? trace_hardirqs_on_caller+0xff/0x220
  [<ffffffff81841341>] ? _raw_spin_unlock_irq+0x41/0x60
  [<ffffffff81137c30>] ? rcu_barrier+0x20/0x20
  [<ffffffff810d2014>] kthread+0x104/0x120
  [<ffffffff81841330>] ? _raw_spin_unlock_irq+0x30/0x60
  [<ffffffff810d1f10>] ? kthread_create_on_node+0x260/0x260
  [<ffffffff8184231f>] ret_from_fork+0x3f/0x70
  [<ffffffff810d1f10>] ? kthread_create_on_node+0x260/0x260
Signed-off-by: default avatarDaniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-rt-users@vger.kernel.org
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1455871601-27484-5-git-send-email-wagi@monom.orgSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      065bb78c
    • Marcelo Tosatti's avatar
      KVM: Use simple waitqueue for vcpu->wq · 8577370f
      Marcelo Tosatti authored 
      The problem:

On -rt, an emulated LAPIC timer instances has the following path:

1) hard interrupt
2) ksoftirqd is scheduled
3) ksoftirqd wakes up vcpu thread
4) vcpu thread is scheduled

This extra context switch introduces unnecessary latency in the
LAPIC path for a KVM guest.

The solution:

Allow waking up vcpu thread from hardirq context,
thus avoiding the need for ksoftirqd to be scheduled.

Normal waitqueues make use of spinlocks, which on -RT
are sleepable locks. Therefore, waking up a waitqueue
waiter involves locking a sleeping lock, which
is not allowed from hard interrupt context.

cyclictest command line:

This patch reduces the average latency in my tests from 14us to 11us.

Daniel writes:
Paolo asked for numbers from kvm-unit-tests/tscdeadline_latency
benchmark on mainline. The test was run 1000 times on
tip/sched/core 4.4.0-rc8-01134-g0905f04e:

  ./x86-run x86/tscdeadline_latency.flat -cpu host

with idle=poll.

The test seems not to deliver really stable numbers though most of
them are smaller. Paolo write:

"Anything above ~10000 cycles means that the host went to C1 or
lower---the number means more or less nothing in that case.

The mean shows an improvement indeed."

Before:

               min             max         mean           std
count  1000.000000     1000.000000  1000.000000   1000.000000
mean   5162.596000  2019270.084000  5824.491541  20681.645558
std      75.431231   622607.723969    89.575700   6492.272062
min    4466.000000    23928.000000  5537.926500    585.864966
25%    5163.000000  16132529.750000  5790.132275  16683.745433
50%    5175.000000  2281919.000000  5834.654000  23151.990026
75%    5190.000000  2382865.750000  5861.412950  24148.206168
max    5228.000000  4175158.000000  6254.827300  46481.048691

After
               min            max         mean           std
count  1000.000000     1000.00000  1000.000000   1000.000000
mean   5143.511000  2076886.10300  5813.312474  21207.357565
std      77.668322   610413.09583    86.541500   6331.915127
min    4427.000000    25103.00000  5529.756600    559.187707
25%    5148.000000  1691272.75000  5784.889825  17473.518244
50%    5160.000000  2308328.50000  5832.025000  23464.837068
75%    5172.000000  2393037.75000  5853.177675  24223.969976
max    5222.000000  3922458.00000  6186.720500  42520.379830

[Patch was originaly based on the swait implementation found in the -rt
 tree. Daniel ported it to mainline's version and gathered the
 benchmark numbers for tscdeadline_latency test.]
Signed-off-by: default avatarDaniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-rt-users@vger.kernel.org
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1455871601-27484-4-git-send-email-wagi@monom.orgSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      8577370f
    • Daniel Wagner's avatar
      kbuild: Add option to turn incompatible pointer check into error · ef50c046
      Daniel Wagner authored 
      With the introduction of the simple wait API we have two very
similar APIs in the kernel. For example wake_up() and swake_up()
is only one character away. Although the compiler will warn
happily the wrong usage it keeps on going an even links the kernel.
Thomas and Peter would rather like to see early missuses reported
as error early on.

In a first attempt we tried to wrap all swait and wait calls
into a macro which has an compile time type assertion. The result
was pretty ugly and wasn't able to catch all wrong usages.
woken_wake_function(), autoremove_wake_function() and wake_bit_function()
are assigned as function pointers. Wrapping them with a macro around is
not possible. Prefixing them with '_' was also not a real option
because there some users in the kernel which do use them as well.
All in all this attempt looked to intrusive and too ugly.

An alternative is to turn the pointer type check into an error which
catches wrong type uses. Obviously not only the swait/wait ones. That
isn't a bad thing either.
Signed-off-by: default avatarDaniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-rt-users@vger.kernel.org
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1455871601-27484-3-git-send-email-wagi@monom.orgSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      ef50c046
    • Peter Zijlstra (Intel)'s avatar
      wait.[ch]: Introduce the simple waitqueue (swait) implementation · 13b35686
      Peter Zijlstra (Intel) authored 
      The existing wait queue support has support for custom wake up call
backs, wake flags, wake key (passed to call back) and exclusive
flags that allow wakers to be tagged as exclusive, for limiting
the number of wakers.

In a lot of cases, none of these features are used, and hence we
can benefit from a slimmed down version that lowers memory overhead
and reduces runtime overhead.

The concept originated from -rt, where waitqueues are a constant
source of trouble, as we can't convert the head lock to a raw
spinlock due to fancy and long lasting callbacks.

With the removal of custom callbacks, we can use a raw lock for
queue list manipulations, hence allowing the simple wait support
to be used in -rt.

[Patch is from PeterZ which is based on Thomas version. Commit message is
 written by Paul G.
 Daniel:  - Fixed some compile issues
 	  - Added non-lazy implementation of swake_up_locked as suggested
	     by Boqun Feng.]
Originally-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarDaniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-rt-users@vger.kernel.org
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1455871601-27484-2-git-send-email-wagi@monom.orgSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      13b35686
  3. 24 Feb, 2016 1 commit
  5. 17 Feb, 2016 1 commit
  7. 09 Feb, 2016 2 commits
    • Rik van Riel's avatar
      sched/numa: Spread memory according to CPU and memory use · 4142c3eb
      Rik van Riel authored 
      The pseudo-interleaving in NUMA placement has a fundamental problem:
using hard usage thresholds to spread memory equally between nodes
can prevent workloads from converging, or keep memory "trapped" on
nodes where the workload is barely running any more.

In order for workloads to properly converge, the memory migration
should not be stopped when nodes reach parity, but instead be
distributed according to how heavily memory is used from each node.
This way memory migration and task migration reinforce each other,
instead of one putting the brakes on the other.

Remove the hard thresholds from the pseudo-interleaving code, and
instead use a more gradual policy on memory placement. This also
seems to improve convergence of workloads that do not run flat out,
but sleep in between bursts of activity.

We still want to slow down NUMA scanning and migration once a workload
has settled on a few actively used nodes, so keep the 3/4 hysteresis
in place. Keep track of whether a workload is actively running on
multiple nodes, so task_numa_migrate does a full scan of the system
for better task placement.

In the case of running 3 SPECjbb2005 instances on a 4 node system,
this code seems to result in fairer distribution of memory between
nodes, with more memory bandwidth for each instance.
Signed-off-by: default avatarRik van Riel <riel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: mgorman@suse.de
Link: http://lkml.kernel.org/r/20160125170739.2fc9a641@annuminas.surriel.com
[ Minor readability tweaks. ]
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      4142c3eb
    • Mel Gorman's avatar
      sched/debug: Make schedstats a runtime tunable that is disabled by default · cb251765
      Mel Gorman authored 
      schedstats is very useful during debugging and performance tuning but it
incurs overhead to calculate the stats. As such, even though it can be
disabled at build time, it is often enabled as the information is useful.

This patch adds a kernel command-line and sysctl tunable to enable or
disable schedstats on demand (when it's built in). It is disabled
by default as someone who knows they need it can also learn to enable
it when necessary.

The benefits are dependent on how scheduler-intensive the workload is.
If it is then the patch reduces the number of cycles spent calculating
the stats with a small benefit from reducing the cache footprint of the
scheduler.

These measurements were taken from a 48-core 2-socket
machine with Xeon(R) E5-2670 v3 cpus although they were also tested on a
single socket machine 8-core machine with Intel i7-3770 processors.

netperf-tcp
                           4.5.0-rc1             4.5.0-rc1
                             vanilla          nostats-v3r1
Hmean    64         560.45 (  0.00%)      575.98 (  2.77%)
Hmean    128        766.66 (  0.00%)      795.79 (  3.80%)
Hmean    256        950.51 (  0.00%)      981.50 (  3.26%)
Hmean    1024      1433.25 (  0.00%)     1466.51 (  2.32%)
Hmean    2048      2810.54 (  0.00%)     2879.75 (  2.46%)
Hmean    3312      4618.18 (  0.00%)     4682.09 (  1.38%)
Hmean    4096      5306.42 (  0.00%)     5346.39 (  0.75%)
Hmean    8192     10581.44 (  0.00%)    10698.15 (  1.10%)
Hmean    16384    18857.70 (  0.00%)    18937.61 (  0.42%)

Small gains here, UDP_STREAM showed nothing intresting and neither did
the TCP_RR tests. The gains on the 8-core machine were very similar.

tbench4
                                 4.5.0-rc1             4.5.0-rc1
                                   vanilla          nostats-v3r1
Hmean    mb/sec-1         500.85 (  0.00%)      522.43 (  4.31%)
Hmean    mb/sec-2         984.66 (  0.00%)     1018.19 (  3.41%)
Hmean    mb/sec-4        1827.91 (  0.00%)     1847.78 (  1.09%)
Hmean    mb/sec-8        3561.36 (  0.00%)     3611.28 (  1.40%)
Hmean    mb/sec-16       5824.52 (  0.00%)     5929.03 (  1.79%)
Hmean    mb/sec-32      10943.10 (  0.00%)    10802.83 ( -1.28%)
Hmean    mb/sec-64      15950.81 (  0.00%)    16211.31 (  1.63%)
Hmean    mb/sec-128     15302.17 (  0.00%)    15445.11 (  0.93%)
Hmean    mb/sec-256     14866.18 (  0.00%)    15088.73 (  1.50%)
Hmean    mb/sec-512     15223.31 (  0.00%)    15373.69 (  0.99%)
Hmean    mb/sec-1024    14574.25 (  0.00%)    14598.02 (  0.16%)
Hmean    mb/sec-2048    13569.02 (  0.00%)    13733.86 (  1.21%)
Hmean    mb/sec-3072    12865.98 (  0.00%)    13209.23 (  2.67%)

Small gains of 2-4% at low thread counts and otherwise flat.  The
gains on the 8-core machine were slightly different

tbench4 on 8-core i7-3770 single socket machine
Hmean    mb/sec-1        442.59 (  0.00%)      448.73 (  1.39%)
Hmean    mb/sec-2        796.68 (  0.00%)      794.39 ( -0.29%)
Hmean    mb/sec-4       1322.52 (  0.00%)     1343.66 (  1.60%)
Hmean    mb/sec-8       2611.65 (  0.00%)     2694.86 (  3.19%)
Hmean    mb/sec-16      2537.07 (  0.00%)     2609.34 (  2.85%)
Hmean    mb/sec-32      2506.02 (  0.00%)     2578.18 (  2.88%)
Hmean    mb/sec-64      2511.06 (  0.00%)     2569.16 (  2.31%)
Hmean    mb/sec-128     2313.38 (  0.00%)     2395.50 (  3.55%)
Hmean    mb/sec-256     2110.04 (  0.00%)     2177.45 (  3.19%)
Hmean    mb/sec-512     2072.51 (  0.00%)     2053.97 ( -0.89%)

In constract, this shows a relatively steady 2-3% gain at higher thread
counts. Due to the nature of the patch and the type of workload, it's
not a surprise that the result will depend on the CPU used.

hackbench-pipes
                         4.5.0-rc1             4.5.0-rc1
                           vanilla          nostats-v3r1
Amean    1        0.0637 (  0.00%)      0.0660 ( -3.59%)
Amean    4        0.1229 (  0.00%)      0.1181 (  3.84%)
Amean    7        0.1921 (  0.00%)      0.1911 (  0.52%)
Amean    12       0.3117 (  0.00%)      0.2923 (  6.23%)
Amean    21       0.4050 (  0.00%)      0.3899 (  3.74%)
Amean    30       0.4586 (  0.00%)      0.4433 (  3.33%)
Amean    48       0.5910 (  0.00%)      0.5694 (  3.65%)
Amean    79       0.8663 (  0.00%)      0.8626 (  0.43%)
Amean    110      1.1543 (  0.00%)      1.1517 (  0.22%)
Amean    141      1.4457 (  0.00%)      1.4290 (  1.16%)
Amean    172      1.7090 (  0.00%)      1.6924 (  0.97%)
Amean    192      1.9126 (  0.00%)      1.9089 (  0.19%)

Some small gains and losses and while the variance data is not included,
it's close to the noise. The UMA machine did not show anything particularly
different

pipetest
                             4.5.0-rc1             4.5.0-rc1
                               vanilla          nostats-v2r2
Min         Time        4.13 (  0.00%)        3.99 (  3.39%)
1st-qrtle   Time        4.38 (  0.00%)        4.27 (  2.51%)
2nd-qrtle   Time        4.46 (  0.00%)        4.39 (  1.57%)
3rd-qrtle   Time        4.56 (  0.00%)        4.51 (  1.10%)
Max-90%     Time        4.67 (  0.00%)        4.60 (  1.50%)
Max-93%     Time        4.71 (  0.00%)        4.65 (  1.27%)
Max-95%     Time        4.74 (  0.00%)        4.71 (  0.63%)
Max-99%     Time        4.88 (  0.00%)        4.79 (  1.84%)
Max         Time        4.93 (  0.00%)        4.83 (  2.03%)
Mean        Time        4.48 (  0.00%)        4.39 (  1.91%)
Best99%Mean Time        4.47 (  0.00%)        4.39 (  1.91%)
Best95%Mean Time        4.46 (  0.00%)        4.38 (  1.93%)
Best90%Mean Time        4.45 (  0.00%)        4.36 (  1.98%)
Best50%Mean Time        4.36 (  0.00%)        4.25 (  2.49%)
Best10%Mean Time        4.23 (  0.00%)        4.10 (  3.13%)
Best5%Mean  Time        4.19 (  0.00%)        4.06 (  3.20%)
Best1%Mean  Time        4.13 (  0.00%)        4.00 (  3.39%)

Small improvement and similar gains were seen on the UMA machine.

The gain is small but it stands to reason that doing less work in the
scheduler is a good thing. The downside is that the lack of schedstats and
tracepoints may be surprising to experts doing performance analysis until
they find the existence of the schedstats= parameter or schedstats sysctl.
It will be automatically activated for latencytop and sleep profiling to
alleviate the problem. For tracepoints, there is a simple warning as it's
not safe to activate schedstats in the context when it's known the tracepoint
may be wanted but is unavailable.
Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
Reviewed-by: default avatarMatt Fleming <matt@codeblueprint.co.uk>
Reviewed-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <mgalbraith@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1454663316-22048-1-git-send-email-mgorman@techsingularity.netSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
      cb251765
  9. 05 Feb, 2016 1 commit
  11. 03 Feb, 2016 24 commits
  13. 01 Feb, 2016 6 commits
    • Linus Torvalds's avatar
      Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net · 34229b27
      Linus Torvalds authored 
      Pull networking fixes from David Miller:
 "This looks like a lot but it's a mixture of regression fixes as well
  as fixes for longer standing issues.

   1) Fix on-channel cancellation in mac80211, from Johannes Berg.

   2) Handle CHECKSUM_COMPLETE properly in xt_TCPMSS netfilter xtables
      module, from Eric Dumazet.

   3) Avoid infinite loop in UDP SO_REUSEPORT logic, also from Eric
      Dumazet.

   4) Avoid a NULL deref if we try to set SO_REUSEPORT after a socket is
      bound, from Craig Gallek.

   5) GRO key comparisons don't take lightweight tunnels into account,
      from Jesse Gross.

   6) Fix struct pid leak via SCM credentials in AF_UNIX, from Eric
      Dumazet.

   7) We need to set the rtnl_link_ops of ipv6 SIT tunnels before we
      register them, otherwise the NEWLINK netlink message is missing
      the proper attributes.  From Thadeu Lima de Souza Cascardo.

   8) Several Spectrum chip bug fixes for mlxsw switch driver, from Ido
      Schimmel

   9) Handle fragments properly in ipv4 easly socket demux, from Eric
      Dumazet.

  10) Don't ignore the ifindex key specifier on ipv6 output route
      lookups, from Paolo Abeni"

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (128 commits)
  tcp: avoid cwnd undo after receiving ECN
  irda: fix a potential use-after-free in ircomm_param_request
  net: tg3: avoid uninitialized variable warning
  net: nb8800: avoid uninitialized variable warning
  net: vxge: avoid unused function warnings
  net: bgmac: clarify CONFIG_BCMA dependency
  net: hp100: remove unnecessary #ifdefs
  net: davinci_cpdma: use dma_addr_t for DMA address
  ipv6/udp: use sticky pktinfo egress ifindex on connect()
  ipv6: enforce flowi6_oif usage in ip6_dst_lookup_tail()
  netlink: not trim skb for mmaped socket when dump
  vxlan: fix a out of bounds access in __vxlan_find_mac
  net: dsa: mv88e6xxx: fix port VLAN maps
  fib_trie: Fix shift by 32 in fib_table_lookup
  net: moxart: use correct accessors for DMA memory
  ipv4: ipconfig: avoid unused ic_proto_used symbol
  bnxt_en: Fix crash in bnxt_free_tx_skbs() during tx timeout.
  bnxt_en: Exclude rx_drop_pkts hw counter from the stack's rx_dropped counter.
  bnxt_en: Ring free response from close path should use completion ring
  net_sched: drr: check for NULL pointer in drr_dequeue
  ...
      34229b27
    • Linus Torvalds's avatar
      Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 · 2c923414
      Linus Torvalds authored 
      Pull crypto fixes from Herbert Xu:
 "This fixes the following issues:

  API:
   - algif_hash needs to wait for init operations to complete.
   - The has_key setting for shash was always true.

  Algorithms:
   - Add missing selections of CRYPTO_HASH.
   - Fix pkcs7 authentication.

  Drivers:
   - Fix stack alignment bug in chacha20-ssse3.
   - Fix performance regression in caam due to incorrect setting.
   - Fix potential compile-only build failure of stm32"

* 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6:
  crypto: atmel-aes - remove calls of clk_prepare() from atomic contexts
  crypto: algif_hash - wait for crypto_ahash_init() to complete
  crypto: shash - Fix has_key setting
  hwrng: stm32 - Fix dependencies for !HAS_IOMEM archs
  crypto: ghash,poly1305 - select CRYPTO_HASH where needed
  crypto: chacha20-ssse3 - Align stack pointer to 64 bytes
  PKCS#7: Don't require SpcSpOpusInfo in Authenticode pkcs7 signatures
  crypto: caam - make write transactions bufferable on PPC platforms
      2c923414
    • Linus Torvalds's avatar
      Merge branch 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm · 29a8ea4f
      Linus Torvalds authored 
      Pull libnvdimm fixes from Dan Williams:
 "1/ Fixes to the libnvdimm 'pfn' device that establishes a reserved
     area for storing a struct page array.

  2/ Fixes for dax operations on a raw block device to prevent pagecache
     collisions with dax mappings.

  3/ A fix for pfn_t usage in vm_insert_mixed that lead to a null
     pointer de-reference.

  These have received build success notification from the kbuild robot
  across 153 configs and pass the latest ndctl tests"

* 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  phys_to_pfn_t: use phys_addr_t
  mm: fix pfn_t to page conversion in vm_insert_mixed
  block: use DAX for partition table reads
  block: revert runtime dax control of the raw block device
  fs, block: force direct-I/O for dax-enabled block devices
  devm_memremap_pages: fix vmem_altmap lifetime + alignment handling
  libnvdimm, pfn: fix restoring memmap location
  libnvdimm: fix mode determination for e820 devices
      29a8ea4f
    • Linus Torvalds's avatar
      Linux 4.5-rc2 · 36f90b0a
      Linus Torvalds authored
      36f90b0a
    • Linus Torvalds's avatar
      Merge tag 'usb-4.5-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb · d784ef58
      Linus Torvalds authored 
      Pull USB driver fixes from Greg KH:
 "Here are some small USB fixes and new device ids for 4.5-rc2.  Nothing
  major here, full details are in the shortlog, and all of these have
  been in linux-next successfully"

* tag 'usb-4.5-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb:
  USB: option: fix Cinterion AHxx enumeration
  USB: mxu11x0: fix memory leak on usb_serial private data
  USB: serial: ftdi_sio: add support for Yaesu SCU-18 cable
  USB: serial: option: Adding support for Telit LE922
  USB: serial: visor: fix crash on detecting device without write_urbs
  USB: visor: fix null-deref at probe
  USB: cp210x: add ID for IAI USB to RS485 adaptor
  usb: hub: do not clear BOS field during reset device
  cdc-acm:exclude Samsung phone 04e8:685d
  usb: cdc-acm: send zero packet for intel 7260 modem
  usb: cdc-acm: handle unlinked urb in acm read callback
      d784ef58
    • Linus Torvalds's avatar
      Merge tag 'tty-4.5-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty · 54e3f3e3
      Linus Torvalds authored 
      Pull tty/serial fixes from Greg KH:
 "Here are some small tty/serial driver fixes for 4.5-rc2.

  They resolve a number of reported problems (the ioctl one specifically
  has been pointed out by numerous people) and one patch adds some new
  device ids for the 8250_pci driver.  All have been in linux-next
  successfully"

* tag 'tty-4.5-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
  serial: 8250_pci: Add Intel Broadwell ports
  staging/speakup: Use tty_ldisc_ref() for paste kworker
  n_tty: Fix unsafe reference to "other" ldisc
  tty: Fix unsafe ldisc reference via ioctl(TIOCGETD)
  tty: Retry failed reopen if tty teardown in-progress
  tty: Wait interruptibly for tty lock on reopen
      54e3f3e3
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