Commit 2056a782 authored by Jens Axboe's avatar Jens Axboe
Browse files

[PATCH] Block queue IO tracing support (blktrace) as of 2006-03-23


Signed-off-by: default avatarJens Axboe <axboe@suse.de>
parent 6dac40a7
......@@ -11,4 +11,16 @@ config LBD
your machine, or if you want to have a raid or loopback device
bigger than 2TB. Otherwise say N.
config BLK_DEV_IO_TRACE
bool "Support for tracing block io actions"
select RELAY
select DEBUG_FS
help
Say Y here, if you want to be able to trace the block layer actions
on a given queue. Tracing allows you to see any traffic happening
on a block device queue. For more information (and the user space
support tools needed), fetch the blktrace app from:
git://brick.kernel.dk/data/git/blktrace.git
source block/Kconfig.iosched
......@@ -8,3 +8,5 @@ obj-$(CONFIG_IOSCHED_NOOP) += noop-iosched.o
obj-$(CONFIG_IOSCHED_AS) += as-iosched.o
obj-$(CONFIG_IOSCHED_DEADLINE) += deadline-iosched.o
obj-$(CONFIG_IOSCHED_CFQ) += cfq-iosched.o
obj-$(CONFIG_BLK_DEV_IO_TRACE) += blktrace.o
/*
* Copyright (C) 2006 Jens Axboe <axboe@suse.de>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
*/
#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/blkdev.h>
#include <linux/blktrace_api.h>
#include <linux/percpu.h>
#include <linux/init.h>
#include <linux/mutex.h>
#include <linux/debugfs.h>
#include <asm/uaccess.h>
static DEFINE_PER_CPU(unsigned long long, blk_trace_cpu_offset) = { 0, };
static unsigned int blktrace_seq __read_mostly = 1;
/*
* Send out a notify for this process, if we haven't done so since a trace
* started
*/
static void trace_note_tsk(struct blk_trace *bt, struct task_struct *tsk)
{
struct blk_io_trace *t;
t = relay_reserve(bt->rchan, sizeof(*t) + sizeof(tsk->comm));
if (t) {
t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
t->device = bt->dev;
t->action = BLK_TC_ACT(BLK_TC_NOTIFY);
t->pid = tsk->pid;
t->cpu = smp_processor_id();
t->pdu_len = sizeof(tsk->comm);
memcpy((void *) t + sizeof(*t), tsk->comm, t->pdu_len);
tsk->btrace_seq = blktrace_seq;
}
}
static int act_log_check(struct blk_trace *bt, u32 what, sector_t sector,
pid_t pid)
{
if (((bt->act_mask << BLK_TC_SHIFT) & what) == 0)
return 1;
if (sector < bt->start_lba || sector > bt->end_lba)
return 1;
if (bt->pid && pid != bt->pid)
return 1;
return 0;
}
/*
* Data direction bit lookup
*/
static u32 ddir_act[2] __read_mostly = { BLK_TC_ACT(BLK_TC_READ), BLK_TC_ACT(BLK_TC_WRITE) };
/*
* Bio action bits of interest
*/
static u32 bio_act[3] __read_mostly = { 0, BLK_TC_ACT(BLK_TC_BARRIER), BLK_TC_ACT(BLK_TC_SYNC) };
/*
* More could be added as needed, taking care to increment the decrementer
* to get correct indexing
*/
#define trace_barrier_bit(rw) \
(((rw) & (1 << BIO_RW_BARRIER)) >> (BIO_RW_BARRIER - 0))
#define trace_sync_bit(rw) \
(((rw) & (1 << BIO_RW_SYNC)) >> (BIO_RW_SYNC - 1))
/*
* The worker for the various blk_add_trace*() types. Fills out a
* blk_io_trace structure and places it in a per-cpu subbuffer.
*/
void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
int rw, u32 what, int error, int pdu_len, void *pdu_data)
{
struct task_struct *tsk = current;
struct blk_io_trace *t;
unsigned long flags;
unsigned long *sequence;
pid_t pid;
int cpu;
if (unlikely(bt->trace_state != Blktrace_running))
return;
what |= ddir_act[rw & WRITE];
what |= bio_act[trace_barrier_bit(rw)];
what |= bio_act[trace_sync_bit(rw)];
pid = tsk->pid;
if (unlikely(act_log_check(bt, what, sector, pid)))
return;
/*
* A word about the locking here - we disable interrupts to reserve
* some space in the relay per-cpu buffer, to prevent an irq
* from coming in and stepping on our toes. Once reserved, it's
* enough to get preemption disabled to prevent read of this data
* before we are through filling it. get_cpu()/put_cpu() does this
* for us
*/
local_irq_save(flags);
if (unlikely(tsk->btrace_seq != blktrace_seq))
trace_note_tsk(bt, tsk);
t = relay_reserve(bt->rchan, sizeof(*t) + pdu_len);
if (t) {
cpu = smp_processor_id();
sequence = per_cpu_ptr(bt->sequence, cpu);
t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
t->sequence = ++(*sequence);
t->time = sched_clock() - per_cpu(blk_trace_cpu_offset, cpu);
t->sector = sector;
t->bytes = bytes;
t->action = what;
t->pid = pid;
t->device = bt->dev;
t->cpu = cpu;
t->error = error;
t->pdu_len = pdu_len;
if (pdu_len)
memcpy((void *) t + sizeof(*t), pdu_data, pdu_len);
}
local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(__blk_add_trace);
static struct dentry *blk_tree_root;
static struct mutex blk_tree_mutex;
static unsigned int root_users;
static inline void blk_remove_root(void)
{
if (blk_tree_root) {
debugfs_remove(blk_tree_root);
blk_tree_root = NULL;
}
}
static void blk_remove_tree(struct dentry *dir)
{
mutex_lock(&blk_tree_mutex);
debugfs_remove(dir);
if (--root_users == 0)
blk_remove_root();
mutex_unlock(&blk_tree_mutex);
}
static struct dentry *blk_create_tree(const char *blk_name)
{
struct dentry *dir = NULL;
mutex_lock(&blk_tree_mutex);
if (!blk_tree_root) {
blk_tree_root = debugfs_create_dir("block", NULL);
if (!blk_tree_root)
goto err;
}
dir = debugfs_create_dir(blk_name, blk_tree_root);
if (dir)
root_users++;
else
blk_remove_root();
err:
mutex_unlock(&blk_tree_mutex);
return dir;
}
static void blk_trace_cleanup(struct blk_trace *bt)
{
relay_close(bt->rchan);
debugfs_remove(bt->dropped_file);
blk_remove_tree(bt->dir);
free_percpu(bt->sequence);
kfree(bt);
}
static int blk_trace_remove(request_queue_t *q)
{
struct blk_trace *bt;
bt = xchg(&q->blk_trace, NULL);
if (!bt)
return -EINVAL;
if (bt->trace_state == Blktrace_setup ||
bt->trace_state == Blktrace_stopped)
blk_trace_cleanup(bt);
return 0;
}
static int blk_dropped_open(struct inode *inode, struct file *filp)
{
filp->private_data = inode->u.generic_ip;
return 0;
}
static ssize_t blk_dropped_read(struct file *filp, char __user *buffer,
size_t count, loff_t *ppos)
{
struct blk_trace *bt = filp->private_data;
char buf[16];
snprintf(buf, sizeof(buf), "%u\n", atomic_read(&bt->dropped));
return simple_read_from_buffer(buffer, count, ppos, buf, strlen(buf));
}
static struct file_operations blk_dropped_fops = {
.owner = THIS_MODULE,
.open = blk_dropped_open,
.read = blk_dropped_read,
};
/*
* Keep track of how many times we encountered a full subbuffer, to aid
* the user space app in telling how many lost events there were.
*/
static int blk_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
void *prev_subbuf, size_t prev_padding)
{
struct blk_trace *bt;
if (!relay_buf_full(buf))
return 1;
bt = buf->chan->private_data;
atomic_inc(&bt->dropped);
return 0;
}
static int blk_remove_buf_file_callback(struct dentry *dentry)
{
debugfs_remove(dentry);
return 0;
}
static struct dentry *blk_create_buf_file_callback(const char *filename,
struct dentry *parent,
int mode,
struct rchan_buf *buf,
int *is_global)
{
return debugfs_create_file(filename, mode, parent, buf,
&relay_file_operations);
}
static struct rchan_callbacks blk_relay_callbacks = {
.subbuf_start = blk_subbuf_start_callback,
.create_buf_file = blk_create_buf_file_callback,
.remove_buf_file = blk_remove_buf_file_callback,
};
/*
* Setup everything required to start tracing
*/
static int blk_trace_setup(request_queue_t *q, struct block_device *bdev,
char __user *arg)
{
struct blk_user_trace_setup buts;
struct blk_trace *old_bt, *bt = NULL;
struct dentry *dir = NULL;
char b[BDEVNAME_SIZE];
int ret, i;
if (copy_from_user(&buts, arg, sizeof(buts)))
return -EFAULT;
if (!buts.buf_size || !buts.buf_nr)
return -EINVAL;
strcpy(buts.name, bdevname(bdev, b));
/*
* some device names have larger paths - convert the slashes
* to underscores for this to work as expected
*/
for (i = 0; i < strlen(buts.name); i++)
if (buts.name[i] == '/')
buts.name[i] = '_';
if (copy_to_user(arg, &buts, sizeof(buts)))
return -EFAULT;
ret = -ENOMEM;
bt = kzalloc(sizeof(*bt), GFP_KERNEL);
if (!bt)
goto err;
bt->sequence = alloc_percpu(unsigned long);
if (!bt->sequence)
goto err;
ret = -ENOENT;
dir = blk_create_tree(buts.name);
if (!dir)
goto err;
bt->dir = dir;
bt->dev = bdev->bd_dev;
atomic_set(&bt->dropped, 0);
ret = -EIO;
bt->dropped_file = debugfs_create_file("dropped", 0444, dir, bt, &blk_dropped_fops);
if (!bt->dropped_file)
goto err;
bt->rchan = relay_open("trace", dir, buts.buf_size, buts.buf_nr, &blk_relay_callbacks);
if (!bt->rchan)
goto err;
bt->rchan->private_data = bt;
bt->act_mask = buts.act_mask;
if (!bt->act_mask)
bt->act_mask = (u16) -1;
bt->start_lba = buts.start_lba;
bt->end_lba = buts.end_lba;
if (!bt->end_lba)
bt->end_lba = -1ULL;
bt->pid = buts.pid;
bt->trace_state = Blktrace_setup;
ret = -EBUSY;
old_bt = xchg(&q->blk_trace, bt);
if (old_bt) {
(void) xchg(&q->blk_trace, old_bt);
goto err;
}
return 0;
err:
if (dir)
blk_remove_tree(dir);
if (bt) {
if (bt->dropped_file)
debugfs_remove(bt->dropped_file);
if (bt->sequence)
free_percpu(bt->sequence);
if (bt->rchan)
relay_close(bt->rchan);
kfree(bt);
}
return ret;
}
static int blk_trace_startstop(request_queue_t *q, int start)
{
struct blk_trace *bt;
int ret;
if ((bt = q->blk_trace) == NULL)
return -EINVAL;
/*
* For starting a trace, we can transition from a setup or stopped
* trace. For stopping a trace, the state must be running
*/
ret = -EINVAL;
if (start) {
if (bt->trace_state == Blktrace_setup ||
bt->trace_state == Blktrace_stopped) {
blktrace_seq++;
smp_mb();
bt->trace_state = Blktrace_running;
ret = 0;
}
} else {
if (bt->trace_state == Blktrace_running) {
bt->trace_state = Blktrace_stopped;
relay_flush(bt->rchan);
ret = 0;
}
}
return ret;
}
/**
* blk_trace_ioctl: - handle the ioctls associated with tracing
* @bdev: the block device
* @cmd: the ioctl cmd
* @arg: the argument data, if any
*
**/
int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
{
request_queue_t *q;
int ret, start = 0;
q = bdev_get_queue(bdev);
if (!q)
return -ENXIO;
mutex_lock(&bdev->bd_mutex);
switch (cmd) {
case BLKTRACESETUP:
ret = blk_trace_setup(q, bdev, arg);
break;
case BLKTRACESTART:
start = 1;
case BLKTRACESTOP:
ret = blk_trace_startstop(q, start);
break;
case BLKTRACETEARDOWN:
ret = blk_trace_remove(q);
break;
default:
ret = -ENOTTY;
break;
}
mutex_unlock(&bdev->bd_mutex);
return ret;
}
/**
* blk_trace_shutdown: - stop and cleanup trace structures
* @q: the request queue associated with the device
*
**/
void blk_trace_shutdown(request_queue_t *q)
{
blk_trace_startstop(q, 0);
blk_trace_remove(q);
}
/*
* Average offset over two calls to sched_clock() with a gettimeofday()
* in the middle
*/
static void blk_check_time(unsigned long long *t)
{
unsigned long long a, b;
struct timeval tv;
a = sched_clock();
do_gettimeofday(&tv);
b = sched_clock();
*t = tv.tv_sec * 1000000000 + tv.tv_usec * 1000;
*t -= (a + b) / 2;
}
static void blk_trace_check_cpu_time(void *data)
{
unsigned long long *t;
int cpu = get_cpu();
t = &per_cpu(blk_trace_cpu_offset, cpu);
/*
* Just call it twice, hopefully the second call will be cache hot
* and a little more precise
*/
blk_check_time(t);
blk_check_time(t);
put_cpu();
}
/*
* Call blk_trace_check_cpu_time() on each CPU to calibrate our inter-CPU
* timings
*/
static void blk_trace_calibrate_offsets(void)
{
unsigned long flags;
smp_call_function(blk_trace_check_cpu_time, NULL, 1, 1);
local_irq_save(flags);
blk_trace_check_cpu_time(NULL);
local_irq_restore(flags);
}
static void blk_trace_set_ht_offsets(void)
{
#if defined(CONFIG_SCHED_SMT)
int cpu, i;
/*
* now make sure HT siblings have the same time offset
*/
preempt_disable();
for_each_online_cpu(cpu) {
unsigned long long *cpu_off, *sibling_off;
for_each_cpu_mask(i, cpu_sibling_map[cpu]) {
if (i == cpu)
continue;
cpu_off = &per_cpu(blk_trace_cpu_offset, cpu);
sibling_off = &per_cpu(blk_trace_cpu_offset, i);
*sibling_off = *cpu_off;
}
}
preempt_enable();
#endif
}
static __init int blk_trace_init(void)
{
mutex_init(&blk_tree_mutex);
blk_trace_calibrate_offsets();
blk_trace_set_ht_offsets();
return 0;
}
module_init(blk_trace_init);
......@@ -33,6 +33,7 @@
#include <linux/init.h>
#include <linux/compiler.h>
#include <linux/delay.h>
#include <linux/blktrace_api.h>
#include <asm/uaccess.h>
......@@ -333,6 +334,8 @@ void elv_insert(request_queue_t *q, struct request *rq, int where)
struct list_head *pos;
unsigned ordseq;
blk_add_trace_rq(q, rq, BLK_TA_INSERT);
rq->q = q;
switch (where) {
......@@ -499,6 +502,7 @@ struct request *elv_next_request(request_queue_t *q)
* not be passed by new incoming requests
*/
rq->flags |= REQ_STARTED;
blk_add_trace_rq(q, rq, BLK_TA_ISSUE);
}
if (!q->boundary_rq || q->boundary_rq == rq) {
......
......@@ -5,6 +5,7 @@
#include <linux/backing-dev.h>
#include <linux/buffer_head.h>
#include <linux/smp_lock.h>
#include <linux/blktrace_api.h>
#include <asm/uaccess.h>
static int blkpg_ioctl(struct block_device *bdev, struct blkpg_ioctl_arg __user *arg)
......@@ -189,6 +190,11 @@ static int blkdev_locked_ioctl(struct file *file, struct block_device *bdev,
return put_ulong(arg, bdev->bd_inode->i_size >> 9);
case BLKGETSIZE64:
return put_u64(arg, bdev->bd_inode->i_size);
case BLKTRACESTART:
case BLKTRACESTOP:
case BLKTRACESETUP:
case BLKTRACETEARDOWN:
return blk_trace_ioctl(bdev, cmd, (char __user *) arg);
}
return -ENOIOCTLCMD;
}
......
......@@ -28,6 +28,7 @@
#include <linux/writeback.h>
#include <linux/interrupt.h>
#include <linux/cpu.h>
#include <linux/blktrace_api.h>
/*
* for max sense size
......@@ -1556,8 +1557,10 @@ void blk_plug_device(request_queue_t *q)
if (test_bit(QUEUE_FLAG_STOPPED, &q->queue_flags))
return;
if (!test_and_set_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags))
if (!test_and_set_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags)) {
mod_timer(&q->unplug_timer, jiffies + q->unplug_delay);
blk_add_trace_generic(q, NULL, 0, BLK_TA_PLUG);
}
}
EXPORT_SYMBOL(blk_plug_device);
......@@ -1621,14 +1624,21 @@ static void blk_backing_dev_unplug(struct backing_dev_info *bdi,
/*
* devices don't necessarily have an ->unplug_fn defined