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Commit c5078f78 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf_counter: provide an mlock threshold 



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: default avatarPeter 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: default avatarIngo Molnar <mingo@elte.hu>
parent 6de6a7b9

include/linux/perf_counter.h

+2 −0
Original line number Diff line number Diff line
@@ -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);

kernel/perf_counter.c

+11 −4
Original line number Diff line number Diff line
@@ -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);

kernel/sysctl.c

+8 −0
Original line number Diff line number Diff line
@@ -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