On Thu, Jul 26, 2007 at 09:53:53AM +0200, Ingo Molnar wrote:
>
> * Ankita Garg <[email protected]> wrote:
>
> > > I'd suggest to not put a probe into a preempt-off section - put it
> > > to the beginning and to the end of schedule() to capture
> > > context-switches. _stp_print_flush() is in the systemtap-generated
> > > module, right? Maybe the problem is resolved by changing that
> > > spinlock to use raw_spinlock_t / DEFINE_RAW_SPIN_LOCK.
> >
> > Yes, _stp_print_flush is in the systemtap-generated kprobe module.
> > Placing the probe at the beginning of schedule() also has the same
> > effect. Will try by changing the spinlock to raw_spinlock_t...
>
> could you send us that module source ST generates? Perhaps there are
> preempt_disable() (or local_irq_disable()) calls in it too.
Attaching the generated module as it is huge...
Looks like SystemTap makes use of relayfs for printing the buffer
contents. The _stp_print_flush() (line 269 in the attached module) implemented
in the systemtap library function as calling the following:
static int _stp_relay_write (const void *data, unsigned length)
{
unsigned long flags;
struct rchan_buf *buf;
if (unlikely(length == 0))
return 0;
local_irq_save(flags);
buf = _stp_chan->buf[smp_processor_id()];
if (unlikely(buf->offset + length > _stp_chan->subbuf_size))
length = relay_switch_subbuf(buf, length);
memcpy(buf->data + buf->offset, data, length);
buf->offset += length;
local_irq_restore(flags);
if (unlikely(length == 0))
return -1;
return length;
}
The above does a local_irq_save().
--
Regards,
Ankita Garg ([email protected])
Linux Technology Center
IBM India Systems & Technology Labs,
Bangalore, India
#define TEST_MODE 0
#ifndef MAXNESTING
#define MAXNESTING 10
#endif
#ifndef MAXSTRINGLEN
#define MAXSTRINGLEN 128
#endif
#ifndef MAXACTION
#define MAXACTION 1000
#endif
#ifndef MAXACTION_INTERRUPTIBLE
#define MAXACTION_INTERRUPTIBLE (MAXACTION * 10)
#endif
#ifndef MAXTRYLOCK
#define MAXTRYLOCK MAXACTION
#endif
#ifndef TRYLOCKDELAY
#define TRYLOCKDELAY 100
#endif
#ifndef MAXMAPENTRIES
#define MAXMAPENTRIES 2048
#endif
#ifndef MAXERRORS
#define MAXERRORS 0
#endif
#ifndef MAXSKIPPED
#define MAXSKIPPED 100
#endif
#ifndef MINSTACKSPACE
#define MINSTACKSPACE 1024
#endif
#ifndef STP_OVERLOAD_INTERVAL
#define STP_OVERLOAD_INTERVAL 1000000000LL
#endif
#ifndef STP_OVERLOAD_THRESHOLD
#define STP_OVERLOAD_THRESHOLD 500000000LL
#endif
#ifndef STP_NO_OVERLOAD
#define STP_OVERLOAD
#endif
#include "runtime.h"
#include "regs.c"
#include "stack.c"
#include "regs-ia64.c"
#include "stat.c"
#include <linux/string.h>
#include <linux/timer.h>
#include <linux/delay.h>
#include <linux/profile.h>
#include <linux/random.h>
#include <linux/utsname.h>
#include "loc2c-runtime.h"
#ifndef read_trylock
#define read_trylock(x) ({ read_lock(x); 1; })
#endif
#if defined(CONFIG_MARKERS)
#include <linux/marker.h>
#endif
typedef char string_t[MAXSTRINGLEN];
#define STAP_SESSION_STARTING 0
#define STAP_SESSION_RUNNING 1
#define STAP_SESSION_ERROR 2
#define STAP_SESSION_STOPPING 3
#define STAP_SESSION_STOPPED 4
atomic_t session_state = ATOMIC_INIT (STAP_SESSION_STARTING);
atomic_t error_count = ATOMIC_INIT (0);
atomic_t skipped_count = ATOMIC_INIT (0);
struct context {
atomic_t busy;
const char *probe_point;
int actionremaining;
unsigned nesting;
const char *last_error;
const char *last_stmt;
struct pt_regs *regs;
struct kretprobe_instance *pi;
va_list mark_va_list;
#ifdef STP_TIMING
Stat *statp;
#endif
#ifdef STP_OVERLOAD
cycles_t cycles_base;
cycles_t cycles_sum;
#endif
union {
struct probe_1493_locals {
string_t argstr;
union {
struct {
string_t __tmp0;
int64_t __tmp1;
int64_t __tmp2;
string_t __tmp3;
};
};
} probe_1493;
struct function_execname_locals {
string_t __retvalue;
} function_execname;
struct function_pid_locals {
int64_t __retvalue;
} function_pid;
struct function_tid_locals {
int64_t __retvalue;
} function_tid;
} locals [MAXNESTING];
};
void *contexts = NULL; /* alloc_percpu */
static void function_execname (struct context * __restrict__ c);
static void function_pid (struct context * __restrict__ c);
static void function_tid (struct context * __restrict__ c);
void function_execname (struct context* __restrict__ c) {
struct function_execname_locals * __restrict__ l =
& c->locals[c->nesting].function_execname;
(void) l;
#define CONTEXT c
#define THIS l
if (0) goto out;
l->__retvalue[0] = '\0';
{
/* pure */
strlcpy (THIS->__retvalue, current->comm, MAXSTRINGLEN);
}
out:
;
#undef CONTEXT
#undef THIS
}
void function_pid (struct context* __restrict__ c) {
struct function_pid_locals * __restrict__ l =
& c->locals[c->nesting].function_pid;
(void) l;
#define CONTEXT c
#define THIS l
if (0) goto out;
l->__retvalue = 0;
{
/* pure */
THIS->__retvalue = current->tgid;
}
out:
;
#undef CONTEXT
#undef THIS
}
void function_tid (struct context* __restrict__ c) {
struct function_tid_locals * __restrict__ l =
& c->locals[c->nesting].function_tid;
(void) l;
#define CONTEXT c
#define THIS l
if (0) goto out;
l->__retvalue = 0;
{
/* pure */
THIS->__retvalue = current->pid;
}
out:
;
#undef CONTEXT
#undef THIS
}
#ifdef STP_TIMING
static __cacheline_aligned Stat time_probe_0;
#endif
static void probe_1493 (struct context * __restrict__ c) {
struct probe_1493_locals * __restrict__ l =
& c->locals[0].probe_1493;
(void) l;
#ifdef STP_TIMING
c->statp = & time_probe_0;
#endif
{
unsigned numtrylock = 0;
(void) numtrylock;
if (0) goto unlock_;
}
l->argstr[0] = '\0';
{
if (unlikely (c->last_error)) goto out;
c->last_stmt = "identifier 'printf' at trace.stp:3:2";
c->actionremaining -= 1;
if (unlikely (c->actionremaining <= 0)) {
c->last_error = "MAXACTION exceeded";
goto out;
}
(void)
({
c->last_stmt = "identifier 'execname' at trace.stp:3:49";
strlcpy (l->__tmp0,
({
if (unlikely (c->nesting+2 >= MAXNESTING)) {
c->last_error = "MAXNESTING exceeded";
c->last_stmt = "identifier 'execname' at trace.stp:3:49";
} else if (likely (! c->last_error)) {
c->nesting ++;
function_execname (c);
c->nesting --;
if (c->last_error && ! c->last_error[0])
c->last_error = 0;
}
c->locals[c->nesting+1].function_execname.__retvalue;
}), MAXSTRINGLEN);
c->last_stmt = "identifier 'pid' at trace.stp:3:61";
l->__tmp1 =
({
if (unlikely (c->nesting+2 >= MAXNESTING)) {
c->last_error = "MAXNESTING exceeded";
c->last_stmt = "identifier 'pid' at trace.stp:3:61";
} else if (likely (! c->last_error)) {
c->nesting ++;
function_pid (c);
c->nesting --;
if (c->last_error && ! c->last_error[0])
c->last_error = 0;
}
c->locals[c->nesting+1].function_pid.__retvalue;
});
c->last_stmt = "identifier 'tid' at trace.stp:3:68";
l->__tmp2 =
({
if (unlikely (c->nesting+2 >= MAXNESTING)) {
c->last_error = "MAXNESTING exceeded";
c->last_stmt = "identifier 'tid' at trace.stp:3:68";
} else if (likely (! c->last_error)) {
c->nesting ++;
function_tid (c);
c->nesting --;
if (c->last_error && ! c->last_error[0])
c->last_error = 0;
}
c->locals[c->nesting+1].function_tid.__retvalue;
});
c->last_stmt = "identifier 'argstr' at trace.stp:3:75";
strlcpy (l->__tmp3, l->argstr, MAXSTRINGLEN);
if (likely (! c->last_error)) {
_stp_printf ("%s (pid: %lld, tid: %lld argstr: %s ) \n", l->__tmp0, l->__tmp1, l->__tmp2, l->__tmp3);
}
((int64_t)0LL);
});
/* null */;
}
out:
_stp_print_flush();
unlock_: ;
}
/* ---- dwarf probes ---- */
#if ! defined(CONFIG_KPROBES)
#error "Need CONFIG_KPROBES!"
#endif
static int enter_kprobe_probe (struct kprobe *inst, struct pt_regs *regs);
static int enter_kretprobe_probe (struct kretprobe_instance *inst, struct pt_regs *regs);
struct stap_dwarf_probe {
union { struct kprobe kp; struct kretprobe krp; } u;
unsigned return_p:1;
unsigned maxactive_p:1;
unsigned registered_p:1;
const char *module;
const char *section;
unsigned long address;
unsigned long maxactive_val;
const char *pp;
void (*ph) (struct context*);
} stap_dwarf_probes[] = {
{ .address=0x2850deUL, .module="kernel", .section="_stext", .pp="kernel.function(\"schedule@kernel/sched.c:3792\")", .ph=&probe_1493 },
};
static int enter_kprobe_probe (struct kprobe *inst, struct pt_regs *regs) {
struct stap_dwarf_probe *sdp = container_of(inst, struct stap_dwarf_probe, u.kp);
struct context* __restrict__ c;
unsigned long flags;
#if defined(STP_TIMING) || defined(STP_OVERLOAD)
cycles_t cycles_atstart = get_cycles ();
#endif
local_irq_save (flags);
if (unlikely ((((unsigned long) (& c)) & (THREAD_SIZE-1))
< (MINSTACKSPACE + sizeof (struct thread_info)))) {
if (unlikely (atomic_inc_return (& skipped_count) > MAXSKIPPED)) {
atomic_set (& session_state, STAP_SESSION_ERROR);
_stp_exit ();
}
goto probe_epilogue;
}
if (atomic_read (&session_state) != STAP_SESSION_RUNNING)
goto probe_epilogue;
c = per_cpu_ptr (contexts, smp_processor_id());
if (unlikely (atomic_inc_return (&c->busy) != 1)) {
if (atomic_inc_return (& skipped_count) > MAXSKIPPED) {
atomic_set (& session_state, STAP_SESSION_ERROR);
_stp_exit ();
}
atomic_dec (& c->busy);
goto probe_epilogue;
}
c->last_error = 0;
c->nesting = 0;
c->regs = 0;
c->pi = 0;
c->probe_point = 0;
c->actionremaining = MAXACTION;
#ifdef STP_TIMING
c->statp = 0;
#endif
c->probe_point = sdp->pp;
c->regs = regs;
(*sdp->ph) (c);
#if defined(STP_TIMING) || defined(STP_OVERLOAD)
{
cycles_t cycles_atend = get_cycles ();
int32_t cycles_elapsed = ((int32_t)cycles_atend > (int32_t)cycles_atstart)
? ((int32_t)cycles_atend - (int32_t)cycles_atstart)
: (~(int32_t)0) - (int32_t)cycles_atstart + (int32_t)cycles_atend + 1;
#ifdef STP_TIMING
if (likely (c->statp)) _stp_stat_add(*c->statp, cycles_elapsed);
#endif
#ifdef STP_OVERLOAD
{
cycles_t interval = (cycles_atend > c->cycles_base)
? (cycles_atend - c->cycles_base)
: (STP_OVERLOAD_INTERVAL + 1);
c->cycles_sum += cycles_elapsed;
if (interval > STP_OVERLOAD_INTERVAL) {
if (c->cycles_sum > STP_OVERLOAD_THRESHOLD) {
_stp_error ("probe overhead exceeded threshold");
atomic_set (&session_state, STAP_SESSION_ERROR);
atomic_inc (&error_count);
}
c->cycles_base = cycles_atend;
c->cycles_sum = 0;
}
}
#endif
}
#endif
if (unlikely (c->last_error && c->last_error[0])) {
if (c->last_stmt != NULL)
_stp_softerror ("%s near %s", c->last_error, c->last_stmt);
else
_stp_softerror ("%s", c->last_error);
atomic_inc (& error_count);
if (atomic_read (& error_count) > MAXERRORS) {
atomic_set (& session_state, STAP_SESSION_ERROR);
_stp_exit ();
}
}
atomic_dec (&c->busy);
probe_epilogue:
local_irq_restore (flags);
return 0;
}
static int enter_kretprobe_probe (struct kretprobe_instance *inst, struct pt_regs *regs) {
struct kretprobe *krp = inst->rp;
struct stap_dwarf_probe *sdp = container_of(krp, struct stap_dwarf_probe, u.krp);
struct context* __restrict__ c;
unsigned long flags;
#if defined(STP_TIMING) || defined(STP_OVERLOAD)
cycles_t cycles_atstart = get_cycles ();
#endif
local_irq_save (flags);
if (unlikely ((((unsigned long) (& c)) & (THREAD_SIZE-1))
< (MINSTACKSPACE + sizeof (struct thread_info)))) {
if (unlikely (atomic_inc_return (& skipped_count) > MAXSKIPPED)) {
atomic_set (& session_state, STAP_SESSION_ERROR);
_stp_exit ();
}
goto probe_epilogue;
}
if (atomic_read (&session_state) != STAP_SESSION_RUNNING)
goto probe_epilogue;
c = per_cpu_ptr (contexts, smp_processor_id());
if (unlikely (atomic_inc_return (&c->busy) != 1)) {
if (atomic_inc_return (& skipped_count) > MAXSKIPPED) {
atomic_set (& session_state, STAP_SESSION_ERROR);
_stp_exit ();
}
atomic_dec (& c->busy);
goto probe_epilogue;
}
c->last_error = 0;
c->nesting = 0;
c->regs = 0;
c->pi = 0;
c->probe_point = 0;
c->actionremaining = MAXACTION;
#ifdef STP_TIMING
c->statp = 0;
#endif
c->probe_point = sdp->pp;
c->regs = regs;
c->pi = inst;
(*sdp->ph) (c);
#if defined(STP_TIMING) || defined(STP_OVERLOAD)
{
cycles_t cycles_atend = get_cycles ();
int32_t cycles_elapsed = ((int32_t)cycles_atend > (int32_t)cycles_atstart)
? ((int32_t)cycles_atend - (int32_t)cycles_atstart)
: (~(int32_t)0) - (int32_t)cycles_atstart + (int32_t)cycles_atend + 1;
#ifdef STP_TIMING
if (likely (c->statp)) _stp_stat_add(*c->statp, cycles_elapsed);
#endif
#ifdef STP_OVERLOAD
{
cycles_t interval = (cycles_atend > c->cycles_base)
? (cycles_atend - c->cycles_base)
: (STP_OVERLOAD_INTERVAL + 1);
c->cycles_sum += cycles_elapsed;
if (interval > STP_OVERLOAD_INTERVAL) {
if (c->cycles_sum > STP_OVERLOAD_THRESHOLD) {
_stp_error ("probe overhead exceeded threshold");
atomic_set (&session_state, STAP_SESSION_ERROR);
atomic_inc (&error_count);
}
c->cycles_base = cycles_atend;
c->cycles_sum = 0;
}
}
#endif
}
#endif
if (unlikely (c->last_error && c->last_error[0])) {
if (c->last_stmt != NULL)
_stp_softerror ("%s near %s", c->last_error, c->last_stmt);
else
_stp_softerror ("%s", c->last_error);
atomic_inc (& error_count);
if (atomic_read (& error_count) > MAXERRORS) {
atomic_set (& session_state, STAP_SESSION_ERROR);
_stp_exit ();
}
}
atomic_dec (&c->busy);
probe_epilogue:
local_irq_restore (flags);
return 0;
}
int systemtap_module_init (void) {
int rc = 0;
int i=0, j=0;
const char *probe_point = "";
down_read (& uts_sem);
{
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,19)
const char* machine = utsname()->machine;
const char* release = utsname()->release;
#else
const char* machine = system_utsname.machine;
const char* release = system_utsname.release;
#endif
if (strcmp (machine, "x86_64")) {
_stp_error ("module machine mismatch (%s vs %s)", machine, "x86_64");
rc = -EINVAL;
}
if (strcmp (release, "2.6.22.1-rt3")) {
_stp_error ("module release mismatch (%s vs %s)", release, "2.6.22.1-rt3");
rc = -EINVAL;
}
}
up_read (& uts_sem);
if (rc) goto out;
(void) probe_point;
(void) i;
(void) j;
atomic_set (&session_state, STAP_SESSION_STARTING);
if (sizeof (struct context) <= 131072)
contexts = alloc_percpu (struct context);
if (contexts == NULL) {
_stp_error ("percpu context (size %lu) allocation failed", sizeof (struct context));
rc = -ENOMEM;
goto out;
}
#ifdef STP_TIMING
time_probe_0 = _stp_stat_init (HIST_NONE);
#endif
for (i=0; i<1; i++) {
struct stap_dwarf_probe *sdp = & stap_dwarf_probes[i];
unsigned long relocated_addr = _stp_module_relocate (sdp->module, sdp->section, sdp->address);
if (relocated_addr == 0) continue;
probe_point = sdp->pp;
if (sdp->return_p) {
sdp->u.krp.kp.addr = (void *) relocated_addr;
if (sdp->maxactive_p) {
sdp->u.krp.maxactive = sdp->maxactive_val;
} else {
sdp->u.krp.maxactive = max(10, 4*NR_CPUS);
}
sdp->u.krp.handler = &enter_kretprobe_probe;
rc = register_kretprobe (& sdp->u.krp);
} else {
sdp->u.kp.addr = (void *) relocated_addr;
sdp->u.kp.pre_handler = &enter_kprobe_probe;
rc = register_kprobe (& sdp->u.kp);
}
if (rc) {
for (j=i-1; j>=0; j--) {
struct stap_dwarf_probe *sdp2 = & stap_dwarf_probes[j];
if (sdp2->return_p) unregister_kretprobe (&sdp2->u.krp);
else unregister_kprobe (&sdp2->u.kp);
}
break;
}
else sdp->registered_p = 1;
}
if (rc) {
_stp_error ("probe %s registration error (rc %d)", probe_point, rc);
atomic_set (&session_state, STAP_SESSION_ERROR);
goto out;
}
printk (KERN_DEBUG "%s: systemtap: 0.5.15/Red Hat elfutils 0.125, base: %p, memory: %lu+%lu+%lu+%lu+%lu data+text+ctx+io+glob, probes: 1\n", THIS_MODULE->name, THIS_MODULE->module_core, (unsigned long) (THIS_MODULE->core_size - THIS_MODULE->core_text_size), (unsigned long) THIS_MODULE->core_text_size, (unsigned long) (num_online_cpus() * sizeof(struct context)), (unsigned long) _stp_allocated_net_memory, (unsigned long) _stp_allocated_memory);
atomic_set (&session_state, STAP_SESSION_RUNNING);
return 0;
out:
return rc;
}
void systemtap_module_exit (void) {
int holdon;
int i=0, j=0;
(void) i;
(void) j;
if (atomic_read (&session_state) == STAP_SESSION_STARTING)
return;
if (atomic_read (&session_state) == STAP_SESSION_RUNNING)
atomic_set (&session_state, STAP_SESSION_STOPPING);
do {
int i;
holdon = 0;
for (i=0; i < NR_CPUS; i++)
if (cpu_possible (i) && atomic_read (& ((struct context *)per_cpu_ptr(contexts, i))->busy)) holdon = 1;
cpu_relax ();
} while (holdon);
for (i=0; i<1; i++) {
struct stap_dwarf_probe *sdp = & stap_dwarf_probes[i];
if (! sdp->registered_p) continue;
if (sdp->return_p) {
unregister_kretprobe (&sdp->u.krp);
atomic_add (sdp->u.krp.nmissed, & skipped_count);
atomic_add (sdp->u.krp.kp.nmissed, & skipped_count);
} else {
unregister_kprobe (&sdp->u.kp);
atomic_add (sdp->u.kp.nmissed, & skipped_count);
}
sdp->registered_p = 0;
}
free_percpu (contexts);
#ifdef STP_TIMING
{
if (likely (time_probe_0)) {
const char *probe_point = "kernel.function(\"schedule\")";
const char *decl_location = "trace.stp:1:1";
struct stat_data *stats = _stp_stat_get (time_probe_0, 0);
const char *error;
if (stats->count) {
int64_t avg = _stp_div64 (&error, stats->sum, stats->count);
_stp_printf ("probe %s (%s), hits: %lld, cycles: %lldmin/%lldavg/%lldmax\n",
probe_point, decl_location, (long long) stats->count, (long long) stats->min, (long long) avg, (long long) stats->max);
}
}
_stp_print_flush();
}
#endif
if (atomic_read (& skipped_count) || atomic_read (& error_count)) {
_stp_printf ("WARNING: Number of errors: %d, skipped probes: %d\n", (int) atomic_read (& error_count), (int) atomic_read (& skipped_count));
_stp_print_flush();
}
}
int probe_start () {
return systemtap_module_init () ? -1 : 0;
}
void probe_exit () {
systemtap_module_exit ();
}
MODULE_DESCRIPTION("systemtap probe");
MODULE_LICENSE("GPL");
/* filled in by runtime */
struct stap_symbol *stap_symbols;
unsigned stap_num_symbols;
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