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perf_counter: provide an mlock threshold

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Provide a threshold to relax the mlock accounting, increasing usability.

Each counter gets perf_counter_mlock_kb for free.

[ Impact: allow more mmap buffering ]

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090505155437.112113632@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-05-05 17:50:24 +02:00 committed by Ingo Molnar
parent 6de6a7b957
commit c5078f78b4
3 changed files with 21 additions and 4 deletions
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2
include/linux/perf_counter.h
View file

@ -358,6 +358,7 @@ struct file;
struct perf_mmap_data {
struct rcu_head rcu_head;
int nr_pages; /* nr of data pages */
int nr_locked; /* nr pages mlocked */
atomic_t poll; /* POLL_ for wakeups */
atomic_t head; /* write position */
@ -575,6 +576,7 @@ struct perf_callchain_entry {
extern struct perf_callchain_entry *perf_callchain(struct pt_regs *regs);
extern int sysctl_perf_counter_priv;
extern int sysctl_perf_counter_mlock;
extern void perf_counter_init(void);

15
kernel/perf_counter.c
View file

@ -44,6 +44,7 @@ static atomic_t nr_munmap_tracking __read_mostly;
static atomic_t nr_comm_tracking __read_mostly;
int sysctl_perf_counter_priv __read_mostly; /* do we need to be privileged */
int sysctl_perf_counter_mlock __read_mostly = 128; /* 'free' kb per counter */
/*
* Lock for (sysadmin-configurable) counter reservations:
@ -1461,7 +1462,7 @@ static void perf_mmap_close(struct vm_area_struct *vma)
if (atomic_dec_and_mutex_lock(&counter->mmap_count,
&counter->mmap_mutex)) {
vma->vm_mm->locked_vm -= counter->data->nr_pages + 1;
vma->vm_mm->locked_vm -= counter->data->nr_locked;
perf_mmap_data_free(counter);
mutex_unlock(&counter->mmap_mutex);
}
@ -1480,6 +1481,7 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
unsigned long nr_pages;
unsigned long locked, lock_limit;
int ret = 0;
long extra;
if (!(vma->vm_flags & VM_SHARED) || (vma->vm_flags & VM_WRITE))
return -EINVAL;
@ -1507,8 +1509,12 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
goto unlock;
}
locked = vma->vm_mm->locked_vm;
locked += nr_pages + 1;
extra = nr_pages /* + 1 only account the data pages */;
extra -= sysctl_perf_counter_mlock >> (PAGE_SHIFT - 10);
if (extra < 0)
extra = 0;
locked = vma->vm_mm->locked_vm + extra;
lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
lock_limit >>= PAGE_SHIFT;
@ -1524,7 +1530,8 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
goto unlock;
atomic_set(&counter->mmap_count, 1);
vma->vm_mm->locked_vm += nr_pages + 1;
vma->vm_mm->locked_vm += extra;
counter->data->nr_locked = extra;
unlock:
mutex_unlock(&counter->mmap_mutex);

8
kernel/sysctl.c
View file

@ -920,6 +920,14 @@ static struct ctl_table kern_table[] = {
.mode = 0644,
.proc_handler = &proc_dointvec,
},
{
.ctl_name = CTL_UNNUMBERED,
.procname = "perf_counter_mlock_kb",
.data = &sysctl_perf_counter_mlock,
.maxlen = sizeof(sysctl_perf_counter_mlock),
.mode = 0644,
.proc_handler = &proc_dointvec,
},
#endif
/*
* NOTE: do not add new entries to this table unless you have read