Currently people use TASK_INTERRUPTIBLE to idle kthreads and wait for
'work' because TASK_UNINTERRUPTIBLE contributes to the loadavg. Having
all idle kthreads contribute to the loadavg is somewhat silly.
Now mostly this works OK, because kthreads have all their signals
masked. However there's a few sites where this is causing problems and
TASK_UNINTERRUPTIBLE should be used, except for that loadavg issue.
This patch adds TASK_NOLOAD which, when combined with
TASK_UNINTERRUPTIBLE avoids the loadavg accounting.
As most of imagined usage sites are loops where a thread wants to
idle, waiting for work, a helper TASK_IDLE is introduced.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Julian Anastasov <ja@ssi.bg>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: NeilBrown <neilb@suse.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This patch adds three tracepoints
o trace_sched_move_numa when a task is moved to a node
o trace_sched_swap_numa when a task is swapped with another task
o trace_sched_stick_numa when a numa-related migration fails
The tracepoints allow the NUMA scheduler activity to be monitored and the
following high-level metrics can be calculated
o NUMA migrated stuck nr trace_sched_stick_numa
o NUMA migrated idle nr trace_sched_move_numa
o NUMA migrated swapped nr trace_sched_swap_numa
o NUMA local swapped trace_sched_swap_numa src_nid == dst_nid (should never happen)
o NUMA remote swapped trace_sched_swap_numa src_nid != dst_nid (should == NUMA migrated swapped)
o NUMA group swapped trace_sched_swap_numa src_ngid == dst_ngid
Maybe a small number of these are acceptable
but a high number would be a major surprise.
It would be even worse if bounces are frequent.
o NUMA avg task migs. Average number of migrations for tasks
o NUMA stddev task mig Self-explanatory
o NUMA max task migs. Maximum number of migrations for a single task
In general the intent of the tracepoints is to help diagnose problems
where automatic NUMA balancing appears to be doing an excessive amount
of useless work.
[akpm@linux-foundation.org: remove semicolon-after-if, repair coding-style]
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Alex Thorlton <athorlton@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Conflicts:
kernel/Makefile
There are conflicts in kernel/Makefile due to file moving in the
scheduler tree - resolve them.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Currently check_hung_task() prints a warning if it detects the
problem, but it is not convenient to watch the system logs if
user-space wants to be notified about the hang.
Add the new trace_sched_process_hang() into check_hung_task(),
this way a user-space monitor can easily wait for the hang and
potentially resolve a problem.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Dave Sullivan <dsulliva@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20131019161828.GA7439@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We need a few special preempt_count accessors:
- task_preempt_count() for when we're interested in the preemption
count of another (non-running) task.
- init_task_preempt_count() for properly initializing the preemption
count.
- init_idle_preempt_count() a special case of the above for the idle
threads.
With these no generic code ever touches thread_info::preempt_count
anymore and architectures could choose to remove it.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-jf5swrio8l78j37d06fzmo4r@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The next patch tries to avoid the costly perf_trace_buf_* calls
when possible but there is a problem. We can only do this if
__task == NULL, perf_tp_event(task != NULL) has the additional
code for this case.
Unfortunately, TP_perf_assign/__perf_xxx which changes the default
values of __count/__task variables for perf_trace_buf_submit() is
called "too late", after we already did perf_trace_buf_prepare(),
and the optimization above can't work.
So this patch simply embeds __perf_xxx() into TP_ARGS(), this way
DECLARE_EVENT_CLASS() can use the result of assignments hidden in
"args" right after ftrace_get_offsets_##call() which is mostly
trivial. This allows us to have the fast-path "__task != NULL"
check at the start, see the next patch.
Link: http://lkml.kernel.org/r/20130806160844.GA2739@redhat.com
Tested-by: David Ahern <dsahern@gmail.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
To simplify the review of the next patches:
1. We are going to reimplent __perf_task/counter and embedd them
into TP_ARGS(). expand TRACE_EVENT(sched_stat_runtime) into
DECLARE_EVENT_CLASS() + DEFINE_EVENT(), this way they can use
different TP_ARGS's.
2. Change perf_trace_##call() macro to do perf_fetch_caller_regs()
right before perf_trace_buf_prepare().
This way it evaluates TP_ARGS() asap, the next patch explores
this fact.
Note: after 87f44bbc perf_trace_buf_prepare() doesn't need
"struct pt_regs *regs", perhaps it makes sense to remove this
argument. And perhaps we can teach perf_trace_buf_submit()
to accept regs == NULL and do fetch_caller_regs(CALLER_ADDR1)
in this case.
3. Cosmetic, but the typecast from "void*" buys nothing. It just
adds the noise, remove it.
Link: http://lkml.kernel.org/r/20130806160841.GA2736@redhat.com
Acked-by: Peter Zijlstra <peterz@infradead.org>
Tested-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The smpboot threads rely on the park/unpark mechanism which binds per
cpu threads on a particular core. Though the functionality is racy:
CPU0 CPU1 CPU2
unpark(T) wake_up_process(T)
clear(SHOULD_PARK) T runs
leave parkme() due to !SHOULD_PARK
bind_to(CPU2) BUG_ON(wrong CPU)
We cannot let the tasks move themself to the target CPU as one of
those tasks is actually the migration thread itself, which requires
that it starts running on the target cpu right away.
The solution to this problem is to prevent wakeups in park mode which
are not from unpark(). That way we can guarantee that the association
of the task to the target cpu is working correctly.
Add a new task state (TASK_PARKED) which prevents other wakeups and
use this state explicitly for the unpark wakeup.
Peter noticed: Also, since the task state is visible to userspace and
all the parked tasks are still in the PID space, its a good hint in ps
and friends that these tasks aren't really there for the moment.
The migration thread has another related issue.
CPU0 CPU1
Bring up CPU2
create_thread(T)
park(T)
wait_for_completion()
parkme()
complete()
sched_set_stop_task()
schedule(TASK_PARKED)
The sched_set_stop_task() call is issued while the task is on the
runqueue of CPU1 and that confuses the hell out of the stop_task class
on that cpu. So we need the same synchronizaion before
sched_set_stop_task().
Reported-by: Dave Jones <davej@redhat.com>
Reported-and-tested-by: Dave Hansen <dave@sr71.net>
Reported-and-tested-by: Borislav Petkov <bp@alien8.de>
Acked-by: Peter Ziljstra <peterz@infradead.org>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: dhillf@gmail.com
Cc: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1304091635430.21884@ionos
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
A few events are interesting not only for a current task.
For example, sched_stat_* events are interesting for a task
which wakes up. For this reason, it will be good if such
events will be delivered to a target task too.
Now a target task can be set by using __perf_task().
The original idea and a draft patch belongs to Peter Zijlstra.
I need these events for profiling sleep times. sched_switch is used for
getting callchains and sched_stat_* is used for getting time periods.
These events are combined in user space, then it can be analyzed by
perf tools.
Inspired-by: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Arun Sharma <asharma@fb.com>
Signed-off-by: Andrew Vagin <avagin@openvz.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1342016098-213063-1-git-send-email-avagin@openvz.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
1. TRACE_EVENT(sched_process_exec) forgets to actually use the
old pid argument, it sets ->old_pid = p->pid.
2. search_binary_handler() uses the wrong pid number. tracepoint
needs the global pid_t from the root namespace, while old_pid
is the virtual pid number as it seen by the tracer/parent.
With this patch we have two pid_t's in search_binary_handler(),
not really nice. Perhaps we should switch to "struct pid*", but
in this case it would be better to cleanup the current code
first and move the "depth == 0" code outside.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: David Smith <dsmith@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Link: http://lkml.kernel.org/r/20120330162636.GA4857@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Added a minimal exec tracepoint. Exec is an important major event
in the life of a task, like fork(), clone() or exit(), all of
which we already trace.
[ We also do scheduling re-balancing during exec() - so it's useful
from a scheduler instrumentation POV as well. ]
If you want to watch a task start up, when it gets exec'ed is a good place
to start. With the addition of this tracepoint, exec's can be monitored
and better picture of general system activity can be obtained. This
tracepoint will also enable better process life tracking, allowing you to
answer questions like "what process keeps starting up binary X?".
This tracepoint can also be useful in ftrace filtering and trigger
conditions: i.e. starting or stopping filtering when exec is called.
Signed-off-by: David Smith <dsmith@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/4F314D19.7030504@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Commit 1ac9bc69 ("sched/tracing: Add a new tracepoint for sleeptime")
added a new sched:sched_stat_sleeptime tracepoint.
It's broken: the first sample we get on a task might be bad because
of a stale sleep_start value that wasn't reset at the last task switch
because the tracepoint was not active.
It also breaks the existing schedstat samples due to the side
effects of:
- se->statistics.sleep_start = 0;
...
- se->statistics.block_start = 0;
Nor do I see means to fix it without adding overhead to the scheduler
fast path, which I'm not willing to for the sake of redundant
instrumentation.
Most importantly, sleep time information can already be constructed
by tracing context switches and wakeups, and taking the timestamp
difference between the schedule-out, the wakeup and the schedule-in.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrew Vagin <avagin@openvz.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/n/tip-pc4c9qhl8q6vg3bs4j6k0rbd@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Convert sched_wait_task to DEFINE_EVENT, and save ~1K:
text data bss dec hex filename
104595 9424 4992 119011 1d0e3 kernel/sched.o.orig
103619 9344 4992 117955 1ccc3 kernel/sched.o
No change in functionality.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4BFA3787.2040800@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
For CONFIG_PREEMPT=y kernels the sched_switch(.prev_state) argument isn't
useful because we can get preempted with current->state != TASK_RUNNING
without actually getting removed from the runqueue.
Cure this by treating all preempted tasks as runnable from the tracer's
point of view.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cautiously-acked-by: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1275322715.27810.23323.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
struct rq isn't visible outside of sched.o so its near useless to
expose the pointer, also there are no users of it, so remove it.
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1272997616.1642.207.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
It is not quite obvious at first sight what TRACE_EVENT_TEMPLATE
does: does it define an event as well beyond defining a template?
To clarify this, rename it to DECLARE_EVENT_CLASS, which follows
the various 'DECLARE_*()' idioms we already have in the kernel:
DECLARE_EVENT_CLASS(class)
DEFINE_EVENT(class, event1)
DEFINE_EVENT(class, event2)
DEFINE_EVENT(class, event3)
To complete this logic we should also rename TRACE_EVENT() to:
DEFINE_SINGLE_EVENT(single_event)
... but in a more quiet moment of the kernel cycle.
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4B0E286A.2000405@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Peter Zijlstra
Oleg Nesterov
Andy Lutomirski
Mel Gorman
Ingo Molnar
Thomas Gleixner
Andrew Vagin
Ingo Molnar
David Smith
Peter Zijlstra
Arun Sharma
Steven Rostedt
Li Zefan
Masami Hiramatsu