Re: [patch 23/24] perfmon3: kernel documentation

From: stephane eranian
Date: Mon Oct 20 2008 - 03:55:18 EST


On Sun, Oct 19, 2008 at 3:37 PM, Pavel Machek <pavel@xxxxxxx> wrote:
> Hi!
>> + * int pfm_create(int flags, pfarg_sinfo_t *s);
>> +
>> + This function creates a perfmon per-thread session.
>> + The flags parameter is currently unused and must be set to 0.
>> +
>> + Upon return and if s is not NULL, the kernel return the list
>> of available
> returns?
pfm_create() returns the file descriptor identifying the session or -1
in case of error + errno set.

>> + PMC and PMD registers. Tools should not assume, they have access to the
>> + entire PMU, it may be shared with other kernel subsystems, e.g., on X86
>> + the NMI watchdog timer.
> How can kernel return anything?
I assume you are talking about pfarg_sinfo_t?
That structure contains bitmasks. If not NULL , the kernel updates the
structure to reflect the
list of available registers.
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