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itimers: remove the per-cpu-ish-ness

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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>
This commit is contained in:
Peter Zijlstra
2008-11-24 17:06:57 +01:00
committed by Ingo Molnar
parent ede6f5aea0
commit 490dea45d0
5 changed files with 46 additions and 107 deletions
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70
kernel/posix-cpu-timers.c
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@@ -9,76 +9,6 @@
#include <asm/uaccess.h>
#include <linux/kernel_stat.h>
/*
* Allocate the thread_group_cputime structure appropriately and fill in the
* current values of the fields. Called from copy_signal() via
* thread_group_cputime_clone_thread() when adding a second or subsequent
* thread to a thread group. Assumes interrupts are enabled when called.
*/
int thread_group_cputime_alloc(struct task_struct *tsk)
{
struct signal_struct *sig = tsk->signal;
struct task_cputime *cputime;
/*
* If we have multiple threads and we don't already have a
* per-CPU task_cputime struct (checked in the caller), allocate
* one and fill it in with the times accumulated so far. We may
* race with another thread so recheck after we pick up the sighand
* lock.
*/
cputime = alloc_percpu(struct task_cputime);
if (cputime == NULL)
return -ENOMEM;
spin_lock_irq(&tsk->sighand->siglock);
if (sig->cputime.totals) {
spin_unlock_irq(&tsk->sighand->siglock);
free_percpu(cputime);
return 0;
}
sig->cputime.totals = cputime;
cputime = per_cpu_ptr(sig->cputime.totals, smp_processor_id());
cputime->utime = tsk->utime;
cputime->stime = tsk->stime;
cputime->sum_exec_runtime = tsk->se.sum_exec_runtime;
spin_unlock_irq(&tsk->sighand->siglock);
return 0;
}
/**
* thread_group_cputime - Sum the thread group time fields across all CPUs.
*
* @tsk: The task we use to identify the thread group.
* @times: task_cputime structure in which we return the summed fields.
*
* Walk the list of CPUs to sum the per-CPU time fields in the thread group
* time structure.
*/
void thread_group_cputime(
struct task_struct *tsk,
struct task_cputime *times)
{
struct task_cputime *totals, *tot;
int i;
totals = tsk->signal->cputime.totals;
if (!totals) {
times->utime = tsk->utime;
times->stime = tsk->stime;
times->sum_exec_runtime = tsk->se.sum_exec_runtime;
return;
}
times->stime = times->utime = cputime_zero;
times->sum_exec_runtime = 0;
for_each_possible_cpu(i) {
tot = per_cpu_ptr(totals, i);
times->utime = cputime_add(times->utime, tot->utime);
times->stime = cputime_add(times->stime, tot->stime);
times->sum_exec_runtime += tot->sum_exec_runtime;
}
}
/*
* Called after updating RLIMIT_CPU to set timer expiration if necessary.
*/