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[IA64] alternate perfmon handler
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Patch from Charles Spirakis

Some linux customers want to optimize their applications on the latest
hardware but are not yet willing to upgrade to the latest kernel. This
patch provides a way to plug in an alternate, basic, and GPL'ed PMU
subsystem to help with their monitoring needs or for specialty work. It
can also be used in case of serious unexpected bugs in perfmon. Mutual
exclusion between the two subsystems is guaranteed, hence no conflict
can arise from both subsystem being present.

Acked-by: Stephane Eranian <eranian@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
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Tony Luck committed May 18, 2005
1 parent 6872ec5 commit a1ecf7f
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Showing 2 changed files with 168 additions and 15 deletions.
175 changes: 160 additions & 15 deletions arch/ia64/kernel/perfmon.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@
* Version Perfmon-2.x is a rewrite of perfmon-1.x
* by Stephane Eranian, Hewlett Packard Co.
*
* Copyright (C) 1999-2003, 2005 Hewlett Packard Co
* Copyright (C) 1999-2005 Hewlett Packard Co
* Stephane Eranian <eranian@hpl.hp.com>
* David Mosberger-Tang <davidm@hpl.hp.com>
*
Expand Down Expand Up @@ -497,6 +497,9 @@ typedef struct {
static pfm_stats_t pfm_stats[NR_CPUS];
static pfm_session_t pfm_sessions; /* global sessions information */

static spinlock_t pfm_alt_install_check;
static pfm_intr_handler_desc_t *pfm_alt_intr_handler;

static struct proc_dir_entry *perfmon_dir;
static pfm_uuid_t pfm_null_uuid = {0,};

Expand Down Expand Up @@ -606,6 +609,7 @@ DEFINE_PER_CPU(unsigned long, pfm_syst_info);
DEFINE_PER_CPU(struct task_struct *, pmu_owner);
DEFINE_PER_CPU(pfm_context_t *, pmu_ctx);
DEFINE_PER_CPU(unsigned long, pmu_activation_number);
EXPORT_SYMBOL_GPL(per_cpu__pfm_syst_info);


/* forward declaration */
Expand Down Expand Up @@ -1325,7 +1329,7 @@ pfm_reserve_session(struct task_struct *task, int is_syswide, unsigned int cpu)
error_conflict:
DPRINT(("system wide not possible, conflicting session [%d] on CPU%d\n",
pfm_sessions.pfs_sys_session[cpu]->pid,
smp_processor_id()));
cpu));
abort:
UNLOCK_PFS(flags);

Expand Down Expand Up @@ -5555,26 +5559,32 @@ pfm_interrupt_handler(int irq, void *arg, struct pt_regs *regs)
int ret;

this_cpu = get_cpu();
min = pfm_stats[this_cpu].pfm_ovfl_intr_cycles_min;
max = pfm_stats[this_cpu].pfm_ovfl_intr_cycles_max;
if (likely(!pfm_alt_intr_handler)) {
min = pfm_stats[this_cpu].pfm_ovfl_intr_cycles_min;
max = pfm_stats[this_cpu].pfm_ovfl_intr_cycles_max;

start_cycles = ia64_get_itc();
start_cycles = ia64_get_itc();

ret = pfm_do_interrupt_handler(irq, arg, regs);
ret = pfm_do_interrupt_handler(irq, arg, regs);

total_cycles = ia64_get_itc();
total_cycles = ia64_get_itc();

/*
* don't measure spurious interrupts
*/
if (likely(ret == 0)) {
total_cycles -= start_cycles;
/*
* don't measure spurious interrupts
*/
if (likely(ret == 0)) {
total_cycles -= start_cycles;

if (total_cycles < min) pfm_stats[this_cpu].pfm_ovfl_intr_cycles_min = total_cycles;
if (total_cycles > max) pfm_stats[this_cpu].pfm_ovfl_intr_cycles_max = total_cycles;
if (total_cycles < min) pfm_stats[this_cpu].pfm_ovfl_intr_cycles_min = total_cycles;
if (total_cycles > max) pfm_stats[this_cpu].pfm_ovfl_intr_cycles_max = total_cycles;

pfm_stats[this_cpu].pfm_ovfl_intr_cycles += total_cycles;
pfm_stats[this_cpu].pfm_ovfl_intr_cycles += total_cycles;
}
}
else {
(*pfm_alt_intr_handler->handler)(irq, arg, regs);
}

put_cpu_no_resched();
return IRQ_HANDLED;
}
Expand Down Expand Up @@ -6425,6 +6435,141 @@ static struct irqaction perfmon_irqaction = {
.name = "perfmon"
};

static void
pfm_alt_save_pmu_state(void *data)
{
struct pt_regs *regs;

regs = ia64_task_regs(current);

DPRINT(("called\n"));

/*
* should not be necessary but
* let's take not risk
*/
pfm_clear_psr_up();
pfm_clear_psr_pp();
ia64_psr(regs)->pp = 0;

/*
* This call is required
* May cause a spurious interrupt on some processors
*/
pfm_freeze_pmu();

ia64_srlz_d();
}

void
pfm_alt_restore_pmu_state(void *data)
{
struct pt_regs *regs;

regs = ia64_task_regs(current);

DPRINT(("called\n"));

/*
* put PMU back in state expected
* by perfmon
*/
pfm_clear_psr_up();
pfm_clear_psr_pp();
ia64_psr(regs)->pp = 0;

/*
* perfmon runs with PMU unfrozen at all times
*/
pfm_unfreeze_pmu();

ia64_srlz_d();
}

int
pfm_install_alt_pmu_interrupt(pfm_intr_handler_desc_t *hdl)
{
int ret, i;
int reserve_cpu;

/* some sanity checks */
if (hdl == NULL || hdl->handler == NULL) return -EINVAL;

/* do the easy test first */
if (pfm_alt_intr_handler) return -EBUSY;

/* one at a time in the install or remove, just fail the others */
if (!spin_trylock(&pfm_alt_install_check)) {
return -EBUSY;
}

/* reserve our session */
for_each_online_cpu(reserve_cpu) {
ret = pfm_reserve_session(NULL, 1, reserve_cpu);
if (ret) goto cleanup_reserve;
}

/* save the current system wide pmu states */
ret = on_each_cpu(pfm_alt_save_pmu_state, NULL, 0, 1);
if (ret) {
DPRINT(("on_each_cpu() failed: %d\n", ret));
goto cleanup_reserve;
}

/* officially change to the alternate interrupt handler */
pfm_alt_intr_handler = hdl;

spin_unlock(&pfm_alt_install_check);

return 0;

cleanup_reserve:
for_each_online_cpu(i) {
/* don't unreserve more than we reserved */
if (i >= reserve_cpu) break;

pfm_unreserve_session(NULL, 1, i);
}

spin_unlock(&pfm_alt_install_check);

return ret;
}
EXPORT_SYMBOL_GPL(pfm_install_alt_pmu_interrupt);

int
pfm_remove_alt_pmu_interrupt(pfm_intr_handler_desc_t *hdl)
{
int i;
int ret;

if (hdl == NULL) return -EINVAL;

/* cannot remove someone else's handler! */
if (pfm_alt_intr_handler != hdl) return -EINVAL;

/* one at a time in the install or remove, just fail the others */
if (!spin_trylock(&pfm_alt_install_check)) {
return -EBUSY;
}

pfm_alt_intr_handler = NULL;

ret = on_each_cpu(pfm_alt_restore_pmu_state, NULL, 0, 1);
if (ret) {
DPRINT(("on_each_cpu() failed: %d\n", ret));
}

for_each_online_cpu(i) {
pfm_unreserve_session(NULL, 1, i);
}

spin_unlock(&pfm_alt_install_check);

return 0;
}
EXPORT_SYMBOL_GPL(pfm_remove_alt_pmu_interrupt);

/*
* perfmon initialization routine, called from the initcall() table
*/
Expand Down
8 changes: 8 additions & 0 deletions include/asm-ia64/perfmon.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -177,6 +177,10 @@ typedef union {

extern long perfmonctl(int fd, int cmd, void *arg, int narg);

typedef struct {
void (*handler)(int irq, void *arg, struct pt_regs *regs);
} pfm_intr_handler_desc_t;

extern void pfm_save_regs (struct task_struct *);
extern void pfm_load_regs (struct task_struct *);

Expand All @@ -187,6 +191,10 @@ extern void pfm_syst_wide_update_task(struct task_struct *, unsigned long info,
extern void pfm_inherit(struct task_struct *task, struct pt_regs *regs);
extern void pfm_init_percpu(void);
extern void pfm_handle_work(void);
extern int pfm_install_alt_pmu_interrupt(pfm_intr_handler_desc_t *h);
extern int pfm_remove_alt_pmu_interrupt(pfm_intr_handler_desc_t *h);



/*
* Reset PMD register flags
Expand Down

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