Change the process wide cpu timers/clocks so that we:
1) don't mess up the kernel with too many threads,
2) don't have a per-cpu allocation for each process,
3) have no impact when not used.
In order to accomplish this we're going to split it into two parts:
- clocks; which can take all the time they want since they run
from user context -- ie. sys_clock_gettime(CLOCK_PROCESS_CPUTIME_ID)
- timers; which need constant time sampling but since they're
explicity used, the user can pay the overhead.
The clock readout will go back to a full sum of the thread group, while the
timers will run of a global 'clock' that only runs when needed, so only
programs that make use of the facility pay the price.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Either we bounce once cacheline per cpu per tick, yielding n^2 bounces
or we just bounce a single..
Also, using per-cpu allocations for the thread-groups complicates the
per-cpu allocator in that its currently aimed to be a fixed sized
allocator and the only possible extention to that would be vmap based,
which is seriously constrained on 32 bit archs.
So making the per-cpu memory requirement depend on the number of
processes is an issue.
Lastly, it didn't deal with cpu-hotplug, although admittedly that might
be fixable.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* 'cpus4096-for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (66 commits)
x86: export vector_used_by_percpu_irq
x86: use logical apicid in x2apic_cluster's x2apic_cpu_mask_to_apicid_and()
sched: nominate preferred wakeup cpu, fix
x86: fix lguest used_vectors breakage, -v2
x86: fix warning in arch/x86/kernel/io_apic.c
sched: fix warning in kernel/sched.c
sched: move test_sd_parent() to an SMP section of sched.h
sched: add SD_BALANCE_NEWIDLE at MC and CPU level for sched_mc>0
sched: activate active load balancing in new idle cpus
sched: bias task wakeups to preferred semi-idle packages
sched: nominate preferred wakeup cpu
sched: favour lower logical cpu number for sched_mc balance
sched: framework for sched_mc/smt_power_savings=N
sched: convert BALANCE_FOR_xx_POWER to inline functions
x86: use possible_cpus=NUM to extend the possible cpus allowed
x86: fix cpu_mask_to_apicid_and to include cpu_online_mask
x86: update io_apic.c to the new cpumask code
x86: Introduce topology_core_cpumask()/topology_thread_cpumask()
x86: xen: use smp_call_function_many()
x86: use work_on_cpu in x86/kernel/cpu/mcheck/mce_amd_64.c
...
Fixed up trivial conflict in kernel/time/tick-sched.c manually
Impact: simplify code
When we turn on CONFIG_SCHEDSTATS, per-task cpu runtime is accumulated
twice. Once in task->se.sum_exec_runtime and once in sched_info.cpu_time.
These two stats are exactly the same.
Given that task->se.sum_exec_runtime is always accumulated by the core
scheduler, sched_info can reuse that data instead of duplicate the accounting.
Signed-off-by: Ken Chen <kenchen@google.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: change calling convention of existing cpumask APIs
Most cpumask functions started with cpus_: these have been replaced by
cpumask_ ones which take struct cpumask pointers as expected.
These four functions don't have good replacement names; fortunately
they're rarely used, so we just change them over.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Mike Travis <travis@sgi.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: paulus@samba.org
Cc: mingo@redhat.com
Cc: tony.luck@intel.com
Cc: ralf@linux-mips.org
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: cl@linux-foundation.org
Cc: srostedt@redhat.com
Impact: trivial wrap of member accesses
This eases the transition in the next patch.
We also get rid of a temporary cpumask in find_idlest_cpu() thanks to
for_each_cpu_and, and sched_balance_self() due to getting weight before
setting sd to NULL.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: fix potential NULL dereference
Contrary to ad474caca3 changelog, other
acct_group_xxx() helpers can be called after exit_notify() by timer tick.
Thanks to Roland for pointing out this. Somehow I missed this simple fact
when I read the original patch, and I am afraid I confused Frank during
the discussion. Sorry.
Fortunately, these helpers work with current, we can check ->exit_state
to ensure that ->signal can't go away under us.
Also, add the comment and compiler barrier to account_group_exec_runtime(),
to make sure we load ->signal only once.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
sched: disable the hrtick for now
sched: revert back to per-rq vruntime
sched: fair scheduler should not resched rt tasks
sched: optimize group load balancer
sched: minor fast-path overhead reduction
sched: fix the wrong mask_len, cleanup
sched: kill unused scheduler decl.
sched: fix the wrong mask_len
sched: only update rq->clock while holding rq->lock
If NR_CPUS isn't a multiple of 32, we get a truncated string of sched
domains by catting /proc/schedstat. This is caused by the wrong mask_len.
This patch fixes it.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Cc: <stable@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
- fix UP lockup
- another set of UP/SMP cleanups and simplifications
Signed-off-by: Frank Mayhar <fmayhar@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This is the second resubmission of the posix timer rework patch, posted
a few days ago.
This includes the changes from the previous resubmittion, which addressed
Oleg Nesterov's comments, removing the RCU stuff from the patch and
un-inlining the thread_group_cputime() function for SMP.
In addition, per Ingo Molnar it simplifies the UP code, consolidating much
of it with the SMP version and depending on lower-level SMP/UP handling to
take care of the differences.
It also cleans up some UP compile errors, moves the scheduler stats-related
macros into kernel/sched_stats.h, cleans up a merge error in
kernel/fork.c and has a few other minor fixes and cleanups as suggested
by Oleg and Ingo. Thanks for the review, guys.
Signed-off-by: Frank Mayhar <fmayhar@google.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
On Thu, Jun 19, 2008 at 12:27:14PM +0200, Peter Zijlstra wrote:
> On Thu, 2008-06-05 at 10:50 +0530, Ankita Garg wrote:
>
> > Thanks Peter for the explanation...
> >
> > I agree with the above and that is the reason why I did not see weird
> > values with cpu_time. But, run_delay still would suffer skews as the end
> > points for delta could be taken on different cpus due to migration (more
> > so on RT kernel due to the push-pull operations). With the below patch,
> > I could not reproduce the issue I had seen earlier. After every dequeue,
> > we take the delta and start wait measurements from zero when moved to a
> > different rq.
>
> OK, so task delay delay accounting is broken because it doesn't take
> migration into account.
>
> What you've done is make it symmetric wrt enqueue, and account it like
>
> cpu0 cpu1
>
> enqueue
> <wait-d1>
> dequeue
> enqueue
> <wait-d2>
> run
>
> Where you add both d1 and d2 to the run_delay,.. right?
>
Thanks for reviewing the patch. The above is exactly what I have done.
> This seems like a good fix, however it looks like the patch will break
> compilation in !CONFIG_SCHEDSTATS && !CONFIG_TASK_DELAY_ACCT, of it
> failing to provide a stub for sched_info_dequeue() in that case.
Fixed. Pl. find the new patch below.
Signed-off-by: Ankita Garg <ankita@in.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Gregory Haskins <ghaskins@novell.com>
Cc: rostedt@goodmis.org
Cc: suresh.b.siddha@intel.com
Cc: aneesh.kumar@linux.vnet.ibm.com
Cc: dhaval@linux.vnet.ibm.com
Cc: vatsa@linux.vnet.ibm.com
Cc: David Bahi <DBahi@novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch corrects the incorrect value of per process run-queue wait
time reported by delay statistics. The anomaly was due to the following
reason. When a process leaves the CPU and immediately starts waiting for
CPU on the runqueue (which means it remains in the TASK_RUNNABLE state),
the time of re-entry into the run-queue is never recorded. Due to this,
the waiting time on the runqueue from this point of re-entry upto the
next time it hits the CPU is not accounted for. This is solved by
recording the time of re-entry of a process leaving the CPU in the
sched_info_depart() function IF the process will go back to waiting on
the run-queue. This IF condition is verified by checking whether the
process is still in the TASK_RUNNABLE state.
The patch was tested on 2.6.26-rc6 using two simple CPU hog programs.
The values noted prior to the fix did not account for the time spent on
the runqueue waiting. After the fix, the correct values were reported
back to user space.
Signed-off-by: Bharath Ravi <bharathravi1@gmail.com>
Signed-off-by: Madhava K R <madhavakr@gmail.com>
Cc: dhaval@linux.vnet.ibm.com
Cc: vatsa@in.ibm.com
Cc: balbir@in.ibm.com
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The Coverity checker spotted a memleak introduced by commit
39106dcf85 (cpumask: use new cpus_scnprintf
function).
It seems the kfree() got lost between v2 and v3 of this patch...
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Cc: Mike Travis <travis@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* Cleaned up references to cpumask_scnprintf() and added new
cpulist_scnprintf() interfaces where appropriate.
* Fix some small bugs (or code efficiency improvments) for various uses
of cpumask_scnprintf.
* Clean up some checkpatch errors.
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Fix the delay accounting regression introduced by commit
75d4ef16a6. rq no longer has sched_info
data associated with it. task_struct sched_info structure is used by delay
accounting to provide back statistics to user space.
also remove direct use of sched_clock() (which is not a valid thing to
do anymore) and use rq->clock instead.
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
schedstat is useful in investigating CPU scheduler behavior. Ideally,
I think it is beneficial to have it on all the time. However, the
cost of turning it on in production system is quite high, largely due
to number of events it collects and also due to its large memory
footprint.
Most of the fields probably don't need to be full 64-bit on 64-bit
arch. Rolling over 4 billion events will most like take a long time
and user space tool can be made to accommodate that. I'm proposing
kernel to cut back most of variable width on 64-bit system. (note,
the following patch doesn't affect 32-bit system).
Signed-off-by: Ken Chen <kenchen@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
rename all 'cnt' fields and variables to the less yucky 'count' name.
yuckage noticed by Andrew Morton.
no change in code, other than the /proc/sched_debug bkl_count string got
a bit larger:
text data bss dec hex filename
38236 3506 24 41766 a326 sched.o.before
38240 3506 24 41770 a32a sched.o.after
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
fix delay accounting performance regression - those sched_clock()
calls are not needed.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
create sched_stats.h and move sched.c schedstats code into it.
This cleans up sched.c a bit.
no code changes are caused by this patch.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Peter Zijlstra