On Mon, 2010-02-08 at 18:21 +0100, Stephane Eranian wrote:
>
> > But before we do that, I think we need to look at the /* hardware */
> > part of struct hw_perf_event, and make that arch specific, we've been
> > growing that a lot lately and I don't think !x86 uses any of that.
I looked at the pahole output:
$ pahole -C hw_perf_event build/arch/x86/kernel/cpu/perf_event.o
struct hw_perf_event {
union {
struct {
u64 config; /* 0 8 */
u64 last_tag; /* 8 8 */
long unsigned int config_base; /* 16 8 */
long unsigned int event_base; /* 24 8 */
int idx; /* 32 4 */
int last_cpu; /* 36 4 */
}; /* 40 */
struct {
s64 remaining; /* 0 8 */
struct hrtimer hrtimer; /* 8 96 */
/* --- cacheline 1 boundary (64 bytes) was 40 bytes ago
--- */
}; /* 104 */
union {
struct arch_hw_breakpoint info; /* 24 */
}; /* 24 */
}; /* 0 104 */
/* --- cacheline 1 boundary (64 bytes) was 40 bytes ago --- */
atomic64_t prev_count; /* 104 8 */
u64 sample_period; /* 112 8 */
u64 last_period; /* 120 8 */
/* --- cacheline 2 boundary (128 bytes) --- */
atomic64_t period_left; /* 128 8 */
u64 interrupts; /* 136 8 */
u64 freq_time_stamp; /* 144 8 */
u64 freq_count_stamp; /* 152 8 */
/* size: 160, cachelines: 3 */
/* last cacheline: 32 bytes */
};
which suggests we still have plenty of room to grow without adding undue
overhead on other architectures, that struct hrtimer is the largest
thing in there.
> It is clear it will need to grow much more to host non-counting features.
> I have played with that myself a few weeks back. So, yes the saved state
> needs to be arch specific.
What do you mean by non-counting features?
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