What:		/sys/kernel/perfmon
Date:		Oct 2008
KernelVersion:	2.6.27
Contact:	eranian@gmail.com

Description:	provide the configuration interface for the perfmon subsystems.
		The tree contains information about the detected hardware,
		current state of the subsystem as well as some configuration
		parameters.

		The tree consists of the following entries:

	/sys/kernel/perfmon/debug (read-write):

		This entry is now obsolete. Perfmon uses pr_XXX() functions
		for debugging. To enable/disable debugging output, refer to
		the documentation about CONFIG_DYNAMIC_PRINTK_DEBUG.

	/sys/kernel/perfmon/pmc_max_fast_arg (read-only):

		Number of perfmon syscall arguments copied directly onto the
		stack (copy_from_user) for pfm_write_pmcs(). Copying to the
		stack avoids having to allocate a buffer. The unit is the
		number of pfarg_pmc_t structures.

	/sys/kernel/perfmon/pmd_max_fast_arg (read-only):

		Number of perfmon syscall arguments copied directly onto the
		stack (copy_from_user) for pfm_write_pmds()/pfm_read_pmds().
		Copying to the stack avoids having to allocate a buffer. The
		unit is the number of pfarg_pmd_t structures.

	/sys/kernel/perfmon/reset_stats (write-only):

		Reset the statistics collected by perfmon. Stats are available
		per-cpu via debugfs.

	/sys/kernel/perfmon/smpl_buffer_mem_cur (read-only):

		Reports the amount of memory currently dedicated to sampling
		buffers by the kernel. The unit is byte.

	/sys/kernel/perfmon/smpl_buffer_mem_max (read-write):

		Maximum amount of kernel memory usable for sampling buffers.
		-1 means everything that is available. Unit is byte.

	/sys/kernel/perfmon/smpl_buffer_mem_cur (read-only):

		Current utilization of kernel memory in bytes.

	/sys/kernel/perfmon/sys_group (read-write):

		Users group allowed to create a system-wide perfmon context
		(session).  -1 means any group.

	/sys/kernel/perfmon/task_group (read-write):

		Users group allowed to create a per-thread context (session).
		-1 means any group.

	/sys/kernel/perfmon/sys_sessions_count (read-only):

		Number of system-wide contexts (sessions) currently attached
		to CPUs.

	/sys/kernel/perfmon/task_sessions_count (read-only):

		Number of per-thread contexts (sessions) currently attached
		to threads.

	/sys/kernel/perfmon/version (read-only):

		Perfmon interface revision number.

	/sys/kernel/perfmon/arg_mem_max(read-write):

		Maximum size of vector arguments expressed in bytes.
		It can be modified but must be at least a page.
		Default: PAGE_SIZE

	/sys/kernel/perfmon/mode(read-write):

		Bitmask to enable/disable certain perfmon features.
		Currently defined:
		- bit 0: if set, then reserved bitfield are ignored on PMC writes

