[PATCH] blk queue io tracing support
From: Jens Axboe
Date: Tue Aug 23 2005 - 07:33:18 EST
Hi,
This is a little something I have played with. It allows you to see
exactly what is going on in the block layer for a given queue. Currently
it can logs request queueing and building, dispatches, requeues, and
completions. I've uploaded a little silly app to do dumps here:
http://www.kernel.org/pub/linux/kernel/people/axboe/tools/blktrace.c
Sample output looks like this:
wiggum:~ # ./blktrace /dev/sda
relay name: /relay/sda0
0 3765 Q R 192-200
5 3765 G R
13 3765 M R [200-208]
15 3765 M R [208-216]
17 3765 M R [216-224]
18 3765 M R [224-232]
19 3765 M R [232-240]
20 3765 M R [240-248]
21 3765 M R [248-256]
154 3765 M R [256-264]
156 3765 M R [264-272]
157 3765 M R [272-280]
159 3765 M R [280-288]
160 3765 M R [288-296]
161 3765 M R [296-304]
162 3765 M R [304-312]
163 3765 M R [312-320]
164 3765 M R [320-328]
170 3765 M R [328-336]
171 3765 M R [336-344]
172 3765 M R [344-352]
173 3765 M R [352-360]
174 3765 M R [360-368]
175 3765 M R [368-376]
177 3765 M R [376-384]
178 3765 M R [384-392]
179 3765 Q R 392-400
180 3765 G R
181 3765 M R [400-408]
182 3765 M R [408-416]
183 3765 M R [416-424]
184 3765 M R [424-432]
185 3765 M R [432-440]
186 3765 M R [440-448]
187 3765 M R [448-456]
189 3765 M R [456-464]
190 3765 M R [464-472]
191 3765 M R [472-480]
193 3765 M R [480-488]
194 3765 M R [488-496]
196 3765 M R [496-504]
197 3765 M R [504-512]
228 3765 D R 192-392
245 3765 D R 392-512
14049 0 C R 192-392 [0]
14067 0 D R 392-512
14807 0 C R 392-512 [0]
Reads: Queued: 2, 160KiB
Completed: 2, 160KiB
Merges: 38
Writes: Queued: 0, 0KiB
Completed: 0, 0KiB
Merges: 0
Events: 47
Missed events: 0
This is a log of a dd if=/dev/sda of=/dev/null bs=64k count=2 and it
shows queueing (Q) and allocation (G) of two requests, along with the
merges (M) that happens there. Finally you see dispatch (D) and
completion (C) of them as well. When sigint is received, blktrace dumps
stats of the current run.
It will work for scsi commands as well, so you can see what is going on
when cdrecord is talking to the device (the cdb is dumped, not the
data). The final integer printed in [] after a completion is the error,
0 for correct completion.
You can register interest in various events, see blktrace.c (grep for
buts and BLKSTARTTRACE).
Patch is against 2.6.13-rc6-mm2. I'm attaching a relayfs update from Tom
Zanussi as well, which is required to handle sub-buffer wrapping
correctly. You need to apply both patches to play with this - and make
sure to enable CONFIG_BLK_DEV_IO_TRACE in your .config, of course. And
blktrace.c relies on relayfs being mounted on /relay, add something ala
none /relay relayfs defaults 0 0
to your /etc/fstab to accomplish that (or do it manually, only
mentioning it for completeness).
--
Jens Axboe
diff -urpN -X /home/axboe/cdrom/exclude /opt/kernel/linux-2.6.13-rc6-mm2/drivers/block/blktrace.c linux-2.6.13-rc6-mm2/drivers/block/blktrace.c
--- /opt/kernel/linux-2.6.13-rc6-mm2/drivers/block/blktrace.c 1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.13-rc6-mm2/drivers/block/blktrace.c 2005-08-23 13:34:17.000000000 +0200
@@ -0,0 +1,119 @@
+#include <linux/config.h>
+#include <linux/kernel.h>
+#include <linux/blkdev.h>
+#include <linux/blktrace.h>
+#include <asm/uaccess.h>
+
+void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
+ int rw, u32 what, int error, int pdu_len, char *pdu_data)
+{
+ struct blk_io_trace t;
+ unsigned long flags;
+
+ if (rw == WRITE)
+ what |= BLK_TC_ACT(BLK_TC_WRITE);
+ else
+ what |= BLK_TC_ACT(BLK_TC_READ);
+
+ if (((bt->act_mask << BLK_TC_SHIFT) & what) == 0)
+ return;
+
+ t.magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
+ t.sequence = atomic_add_return(1, &bt->sequence);
+ t.time = sched_clock() / 1000;
+ t.sector = sector;
+ t.bytes = bytes;
+ t.action = what;
+ t.pid = current->pid;
+ t.error = error;
+ t.pdu_len = pdu_len;
+
+ local_irq_save(flags);
+ __relay_write(bt->rchan, &t, sizeof(t));
+ if (pdu_len)
+ __relay_write(bt->rchan, pdu_data, pdu_len);
+ local_irq_restore(flags);
+}
+
+int blk_stop_trace(struct block_device *bdev)
+{
+ request_queue_t *q = bdev_get_queue(bdev);
+ struct blk_trace *bt = NULL;
+ int ret = -EINVAL;
+
+ if (!q)
+ return -ENXIO;
+
+ down(&bdev->bd_sem);
+
+ spin_lock_irq(q->queue_lock);
+ if (q->blk_trace) {
+ bt = q->blk_trace;
+ q->blk_trace = NULL;
+ ret = 0;
+ }
+ spin_unlock_irq(q->queue_lock);
+
+ up(&bdev->bd_sem);
+
+ if (bt) {
+ relay_close(bt->rchan);
+ kfree(bt);
+ }
+
+ return ret;
+}
+
+int blk_start_trace(struct block_device *bdev, char __user *arg)
+{
+ request_queue_t *q = bdev_get_queue(bdev);
+ struct blk_user_trace_setup buts;
+ struct blk_trace *bt;
+ char b[BDEVNAME_SIZE];
+ int ret = 0;
+
+ if (!q)
+ return -ENXIO;
+
+ 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));
+
+ if (copy_to_user(arg, &buts, sizeof(buts)))
+ return -EFAULT;
+
+ down(&bdev->bd_sem);
+ ret = -EBUSY;
+ if (q->blk_trace)
+ goto err;
+
+ ret = -ENOMEM;
+ bt = kmalloc(sizeof(*bt), GFP_KERNEL);
+ if (!bt)
+ goto err;
+
+ atomic_set(&bt->sequence, 0);
+
+ bt->rchan = relay_open(bdevname(bdev, b), NULL, buts.buf_size,
+ buts.buf_nr, NULL);
+ ret = -EIO;
+ if (!bt->rchan)
+ goto err;
+
+ bt->act_mask = buts.act_mask;
+ if (!bt->act_mask)
+ bt->act_mask = (u16) -1;
+
+ spin_lock_irq(q->queue_lock);
+ q->blk_trace = bt;
+ spin_unlock_irq(q->queue_lock);
+ ret = 0;
+err:
+ up(&bdev->bd_sem);
+ return ret;
+}
+
diff -urpN -X /home/axboe/cdrom/exclude /opt/kernel/linux-2.6.13-rc6-mm2/drivers/block/elevator.c linux-2.6.13-rc6-mm2/drivers/block/elevator.c
--- /opt/kernel/linux-2.6.13-rc6-mm2/drivers/block/elevator.c 2005-08-23 08:23:51.000000000 +0200
+++ linux-2.6.13-rc6-mm2/drivers/block/elevator.c 2005-08-23 08:24:34.000000000 +0200
@@ -34,6 +34,7 @@
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/compiler.h>
+#include <linux/blktrace.h>
#include <asm/uaccess.h>
@@ -371,6 +372,9 @@ struct request *elv_next_request(request
int ret;
while ((rq = __elv_next_request(q)) != NULL) {
+
+ blk_add_trace_rq(q, rq, BLK_TA_ISSUE);
+
/*
* just mark as started even if we don't start it, a request
* that has been delayed should not be passed by new incoming
diff -urpN -X /home/axboe/cdrom/exclude /opt/kernel/linux-2.6.13-rc6-mm2/drivers/block/ioctl.c linux-2.6.13-rc6-mm2/drivers/block/ioctl.c
--- /opt/kernel/linux-2.6.13-rc6-mm2/drivers/block/ioctl.c 2005-08-23 08:23:51.000000000 +0200
+++ linux-2.6.13-rc6-mm2/drivers/block/ioctl.c 2005-08-23 08:33:28.000000000 +0200
@@ -4,6 +4,7 @@
#include <linux/backing-dev.h>
#include <linux/buffer_head.h>
#include <linux/smp_lock.h>
+#include <linux/blktrace.h>
#include <asm/uaccess.h>
static int blkpg_ioctl(struct block_device *bdev, struct blkpg_ioctl_arg __user *arg)
@@ -188,6 +189,10 @@ static int blkdev_locked_ioctl(struct fi
return put_ulong(arg, bdev->bd_inode->i_size >> 9);
case BLKGETSIZE64:
return put_u64(arg, bdev->bd_inode->i_size);
+ case BLKSTARTTRACE:
+ return blk_start_trace(bdev, (char __user *) arg);
+ case BLKSTOPTRACE:
+ return blk_stop_trace(bdev);
}
return -ENOIOCTLCMD;
}
diff -urpN -X /home/axboe/cdrom/exclude /opt/kernel/linux-2.6.13-rc6-mm2/drivers/block/Kconfig linux-2.6.13-rc6-mm2/drivers/block/Kconfig
--- /opt/kernel/linux-2.6.13-rc6-mm2/drivers/block/Kconfig 2005-08-23 08:23:51.000000000 +0200
+++ linux-2.6.13-rc6-mm2/drivers/block/Kconfig 2005-08-23 08:30:20.000000000 +0200
@@ -419,6 +419,14 @@ 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 RELAYFS
+ help
+ Say Y here, if you want to be able to trace the block layer actions
+ on a given queue.
+
+
config CDROM_PKTCDVD
tristate "Packet writing on CD/DVD media"
depends on !UML
diff -urpN -X /home/axboe/cdrom/exclude /opt/kernel/linux-2.6.13-rc6-mm2/drivers/block/ll_rw_blk.c linux-2.6.13-rc6-mm2/drivers/block/ll_rw_blk.c
--- /opt/kernel/linux-2.6.13-rc6-mm2/drivers/block/ll_rw_blk.c 2005-08-23 08:23:51.000000000 +0200
+++ linux-2.6.13-rc6-mm2/drivers/block/ll_rw_blk.c 2005-08-23 08:24:34.000000000 +0200
@@ -29,6 +29,7 @@
#include <linux/swap.h>
#include <linux/writeback.h>
#include <linux/blkdev.h>
+#include <linux/blktrace.h>
/*
* for max sense size
@@ -1625,6 +1626,12 @@ void blk_cleanup_queue(request_queue_t *
if (q->queue_tags)
__blk_queue_free_tags(q);
+ if (q->blk_trace) {
+ relay_close(q->blk_trace->rchan);
+ kfree(q->blk_trace);
+ q->blk_trace = NULL;
+ }
+
blk_queue_ordered(q, QUEUE_ORDERED_NONE);
kmem_cache_free(requestq_cachep, q);
@@ -1971,6 +1978,8 @@ rq_starved:
rq_init(q, rq);
rq->rl = rl;
+
+ blk_add_trace_generic(q, bio, rw, BLK_TA_GETRQ);
out:
return rq;
}
@@ -1999,6 +2008,8 @@ static struct request *get_request_wait(
if (!rq) {
struct io_context *ioc;
+ blk_add_trace_generic(q, bio, rw, BLK_TA_SLEEPRQ);
+
__generic_unplug_device(q);
spin_unlock_irq(q->queue_lock);
io_schedule();
@@ -2052,6 +2063,8 @@ EXPORT_SYMBOL(blk_get_request);
*/
void blk_requeue_request(request_queue_t *q, struct request *rq)
{
+ blk_add_trace_rq(q, rq, BLK_TA_REQUEUE);
+
if (blk_rq_tagged(rq))
blk_queue_end_tag(q, rq);
@@ -2665,6 +2678,8 @@ static int __make_request(request_queue_
if (!q->back_merge_fn(q, req, bio))
break;
+ blk_add_trace_bio(q, bio, BLK_TA_BACKMERGE);
+
req->biotail->bi_next = bio;
req->biotail = bio;
req->nr_sectors = req->hard_nr_sectors += nr_sectors;
@@ -2680,6 +2695,8 @@ static int __make_request(request_queue_
if (!q->front_merge_fn(q, req, bio))
break;
+ blk_add_trace_bio(q, bio, BLK_TA_FRONTMERGE);
+
bio->bi_next = req->bio;
req->bio = bio;
@@ -2705,6 +2722,8 @@ static int __make_request(request_queue_
}
get_rq:
+ blk_add_trace_bio(q, bio, BLK_TA_QUEUE);
+
/*
* Grab a free request. This is might sleep but can not fail.
* Returns with the queue unlocked.
@@ -2981,6 +3000,10 @@ end_io:
blk_partition_remap(bio);
ret = q->make_request_fn(q, bio);
+
+ if (ret)
+ blk_add_trace_bio(q, bio, BLK_TA_QUEUE);
+
} while (ret);
}
@@ -3099,6 +3122,8 @@ static int __end_that_request_first(stru
int total_bytes, bio_nbytes, error, next_idx = 0;
struct bio *bio;
+ blk_add_trace_rq(req->q, req, BLK_TA_COMPLETE);
+
/*
* extend uptodate bool to allow < 0 value to be direct io error
*/
diff -urpN -X /home/axboe/cdrom/exclude /opt/kernel/linux-2.6.13-rc6-mm2/drivers/block/Makefile linux-2.6.13-rc6-mm2/drivers/block/Makefile
--- /opt/kernel/linux-2.6.13-rc6-mm2/drivers/block/Makefile 2005-08-23 08:23:51.000000000 +0200
+++ linux-2.6.13-rc6-mm2/drivers/block/Makefile 2005-08-23 08:51:55.000000000 +0200
@@ -45,3 +45,5 @@ obj-$(CONFIG_VIODASD) += viodasd.o
obj-$(CONFIG_BLK_DEV_SX8) += sx8.o
obj-$(CONFIG_BLK_DEV_UB) += ub.o
+obj-$(CONFIG_BLK_DEV_IO_TRACE) += blktrace.o
+
diff -urpN -X /home/axboe/cdrom/exclude /opt/kernel/linux-2.6.13-rc6-mm2/include/linux/blkdev.h linux-2.6.13-rc6-mm2/include/linux/blkdev.h
--- /opt/kernel/linux-2.6.13-rc6-mm2/include/linux/blkdev.h 2005-08-23 08:24:10.000000000 +0200
+++ linux-2.6.13-rc6-mm2/include/linux/blkdev.h 2005-08-23 08:24:34.000000000 +0200
@@ -22,6 +22,7 @@ typedef struct request_queue request_que
struct elevator_queue;
typedef struct elevator_queue elevator_t;
struct request_pm_state;
+struct blk_trace;
#define BLKDEV_MIN_RQ 4
#define BLKDEV_MAX_RQ 128 /* Default maximum */
@@ -412,6 +413,8 @@ struct request_queue
*/
struct request *flush_rq;
unsigned char ordered;
+
+ struct blk_trace *blk_trace;
};
enum {
diff -urpN -X /home/axboe/cdrom/exclude /opt/kernel/linux-2.6.13-rc6-mm2/include/linux/blktrace.h linux-2.6.13-rc6-mm2/include/linux/blktrace.h
--- /opt/kernel/linux-2.6.13-rc6-mm2/include/linux/blktrace.h 1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.13-rc6-mm2/include/linux/blktrace.h 2005-08-23 13:35:52.000000000 +0200
@@ -0,0 +1,142 @@
+#ifndef BLKTRACE_H
+#define BLKTRACE_H
+
+#include <linux/config.h>
+#include <linux/blkdev.h>
+#include <linux/relayfs_fs.h>
+
+/*
+ * Trace categories
+ */
+enum {
+ BLK_TC_READ = 1 << 0, /* reads */
+ BLK_TC_WRITE = 1 << 1, /* writes */
+ BLK_TC_QUEUE = 1 << 2, /* queueing/merging */
+ BLK_TC_ISSUE = 1 << 3, /* issue */
+ BLK_TC_COMPLETE = 1 << 4, /* completions */
+ BLK_TC_FS = 1 << 5, /* fs requests */
+ BLK_TC_PC = 1 << 6, /* pc requests */
+
+ BLK_TC_END = 1 << 15, /* only 16-bits, reminder */
+};
+
+#define BLK_TC_SHIFT (16)
+#define BLK_TC_ACT(act) ((act) << BLK_TC_SHIFT)
+
+/*
+ * Basic trace actions
+ */
+enum {
+ __BLK_TA_QUEUE = 1, /* queued */
+ __BLK_TA_BACKMERGE, /* back merged to existing rq */
+ __BLK_TA_FRONTMERGE, /* front merge to existing rq */
+ __BLK_TA_GETRQ, /* allocated new request */
+ __BLK_TA_SLEEPRQ, /* sleeping on rq allocation */
+ __BLK_TA_REQUEUE, /* request requeued */
+ __BLK_TA_ISSUE, /* sent to driver */
+ __BLK_TA_COMPLETE, /* completed by driver */
+};
+
+/*
+ * Trace actions in full. Additionally, read or write is masked
+ */
+#define BLK_TA_QUEUE (__BLK_TA_QUEUE | BLK_TC_ACT(BLK_TC_QUEUE))
+#define BLK_TA_BACKMERGE (__BLK_TA_BACKMERGE | BLK_TC_ACT(BLK_TC_QUEUE))
+#define BLK_TA_FRONTMERGE (__BLK_TA_FRONTMERGE | BLK_TC_ACT(BLK_TC_QUEUE))
+#define BLK_TA_GETRQ (__BLK_TA_GETRQ | BLK_TC_ACT(BLK_TC_QUEUE))
+#define BLK_TA_SLEEPRQ (__BLK_TA_SLEEPRQ | BLK_TC_ACT(BLK_TC_QUEUE))
+#define BLK_TA_REQUEUE (__BLK_TA_REQUEUE | BLK_TC_ACT(BLK_TC_QUEUE))
+#define BLK_TA_ISSUE (__BLK_TA_ISSUE | BLK_TC_ACT(BLK_TC_ISSUE))
+#define BLK_TA_COMPLETE (__BLK_TA_COMPLETE| BLK_TC_ACT(BLK_TC_COMPLETE))
+
+#define BLK_IO_TRACE_MAGIC 0x65617400
+#define BLK_IO_TRACE_VERSION 0x01
+
+/*
+ * The trace itself
+ */
+struct blk_io_trace {
+ u32 magic; /* MAGIC << 8 | version */
+ u32 sequence; /* event number */
+ u64 time; /* in microseconds */
+ u64 sector; /* disk offset */
+ u32 bytes; /* transfer length */
+ u32 action; /* what happened */
+ u16 pid; /* who did it */
+ u16 error; /* completion error */
+ u16 pdu_len; /* length of data after this trace */
+};
+
+struct blk_trace {
+ struct rchan *rchan;
+ atomic_t sequence;
+ u16 act_mask;
+};
+
+/*
+ * User setup structure passed with BLKSTARTTRACE
+ */
+struct blk_user_trace_setup {
+ char name[BDEVNAME_SIZE]; /* output */
+ u16 act_mask; /* input */
+ u32 buf_size; /* input */
+ u32 buf_nr; /* input */
+};
+
+#if defined(CONFIG_BLK_DEV_IO_TRACE)
+extern int blk_start_trace(struct block_device *, char __user *);
+extern int blk_stop_trace(struct block_device *);
+extern void __blk_add_trace(struct blk_trace *, sector_t, int, int, u32, int, int, char *);
+
+static inline void blk_add_trace_rq(struct request_queue *q, struct request *rq,
+ u32 what)
+{
+ struct blk_trace *bt = q->blk_trace;
+ int rw = rq_data_dir(rq);
+
+ if (likely(!bt))
+ return;
+
+ if (blk_pc_request(rq)) {
+ what |= BLK_TC_ACT(BLK_TC_PC);
+ __blk_add_trace(bt, 0, rq->data_len, rw, what, rq->errors, sizeof(rq->cmd), rq->cmd);
+ } else {
+ what |= BLK_TC_ACT(BLK_TC_FS);
+ __blk_add_trace(bt, rq->hard_sector, rq->hard_nr_sectors << 9, rw, what, rq->errors, 0, NULL);
+ }
+}
+
+static inline void blk_add_trace_bio(struct request_queue *q, struct bio *bio,
+ u32 what)
+{
+ struct blk_trace *bt = q->blk_trace;
+
+ if (likely(!bt))
+ return;
+
+ __blk_add_trace(bt, bio->bi_sector, bio->bi_size, bio_data_dir(bio), what, !bio_flagged(bio, BIO_UPTODATE), 0, NULL);
+}
+
+static inline void blk_add_trace_generic(struct request_queue *q,
+ struct bio *bio, int rw, u32 what)
+{
+ struct blk_trace *bt = q->blk_trace;
+
+ if (likely(!bt))
+ return;
+
+ if (bio)
+ blk_add_trace_bio(q, bio, what);
+ else
+ __blk_add_trace(bt, 0, 0, rw, what, 0, 0, NULL);
+}
+
+#else /* !CONFIG_BLK_DEV_IO_TRACE */
+#define blk_start_trace(bdev, arg) (-EINVAL)
+#define blk_stop_trace(bdev) (-EINVAL)
+#define blk_add_trace_rq(q, rq, what) do { } while (0)
+#define blk_add_trace_bio(q, rq, what) do { } while (0)
+#define blk_add_trace_generic(q, rq, rw, what) do { } while (0)
+#endif /* CONFIG_BLK_DEV_IO_TRACE */
+
+#endif
diff -urpN -X /home/axboe/cdrom/exclude /opt/kernel/linux-2.6.13-rc6-mm2/include/linux/fs.h linux-2.6.13-rc6-mm2/include/linux/fs.h
--- /opt/kernel/linux-2.6.13-rc6-mm2/include/linux/fs.h 2005-08-23 08:24:10.000000000 +0200
+++ linux-2.6.13-rc6-mm2/include/linux/fs.h 2005-08-23 08:24:34.000000000 +0200
@@ -196,6 +196,8 @@ extern int dir_notify_enable;
#define BLKBSZGET _IOR(0x12,112,size_t)
#define BLKBSZSET _IOW(0x12,113,size_t)
#define BLKGETSIZE64 _IOR(0x12,114,size_t) /* return device size in bytes (u64 *arg) */
+#define BLKSTARTTRACE _IOWR(0x12,115,struct blk_user_trace_setup)
+#define BLKSTOPTRACE _IO(0x12,116)
#define BMAP_IOCTL 1 /* obsolete - kept for compatibility */
#define FIBMAP _IO(0x00,1) /* bmap access */
--- linux-2.6.13-rc6-mm2/fs/relayfs/inode.c~ 2005-08-23 14:29:11.000000000 +0200
+++ linux-2.6.13-rc6-mm2/fs/relayfs/inode.c 2005-08-23 14:29:54.000000000 +0200
@@ -302,94 +302,73 @@
* return the original value.
*/
static inline size_t relayfs_read_start(size_t read_pos,
- size_t avail,
- size_t start_subbuf,
struct rchan_buf *buf)
{
- size_t read_subbuf, adj_read_subbuf;
- size_t padding, padding_start, padding_end;
+ size_t read_subbuf, padding, padding_start, padding_end;
size_t subbuf_size = buf->chan->subbuf_size;
size_t n_subbufs = buf->chan->n_subbufs;
-
+
read_subbuf = read_pos / subbuf_size;
- adj_read_subbuf = (read_subbuf + start_subbuf) % n_subbufs;
-
- if ((read_subbuf + 1) * subbuf_size <= avail) {
- padding = buf->padding[adj_read_subbuf];
- padding_start = (read_subbuf + 1) * subbuf_size - padding;
- padding_end = (read_subbuf + 1) * subbuf_size;
- if (read_pos >= padding_start && read_pos < padding_end) {
- read_subbuf = (read_subbuf + 1) % n_subbufs;
- read_pos = read_subbuf * subbuf_size;
- }
+ padding = buf->padding[read_subbuf];
+ padding_start = (read_subbuf + 1) * subbuf_size - padding;
+ padding_end = (read_subbuf + 1) * subbuf_size;
+ if (read_pos >= padding_start && read_pos < padding_end) {
+ read_subbuf = (read_subbuf + 1) % n_subbufs;
+ read_pos = read_subbuf * subbuf_size;
}
return read_pos;
}
/**
- * relayfs_read_end - return the end of available bytes to read
- *
- * If the read_pos is in the middle of a full sub-buffer, return
- * the padding-adjusted end of that sub-buffer, otherwise return
- * the position after the last byte written to the buffer. At
- * most, 1 sub-buffer can be read at a time.
+ * relayfs_read_avail - return total available along with buffer start
*
+ * Because buffers are circular, the 'beginning' of the buffer
+ * depends on where the buffer was last written. If the writer
+ * has cycled around the buffer, the beginning is defined to be
+ * the beginning of the sub-buffer following the last sub-buffer
+ * written to, otherwise it's the beginning of sub-buffer 0.
+ *
*/
-static inline size_t relayfs_read_end(size_t read_pos,
- size_t avail,
- size_t start_subbuf,
- struct rchan_buf *buf)
+static inline size_t relayfs_read_avail(size_t read_pos,
+ struct rchan_buf *buf)
{
- size_t padding, read_endpos, buf_offset;
- size_t read_subbuf, adj_read_subbuf;
+ size_t padding, avail = 0;
+ size_t read_subbuf, read_offset, write_subbuf, write_offset;
size_t subbuf_size = buf->chan->subbuf_size;
- size_t n_subbufs = buf->chan->n_subbufs;
- buf_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
+ write_subbuf = (buf->data - buf->start) / subbuf_size;
+ write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
read_subbuf = read_pos / subbuf_size;
- adj_read_subbuf = (read_subbuf + start_subbuf) % n_subbufs;
+ read_offset = read_pos % subbuf_size;
+ padding = buf->padding[read_subbuf];
- if ((read_subbuf + 1) * subbuf_size <= avail) {
- padding = buf->padding[adj_read_subbuf];
- read_endpos = (read_subbuf + 1) * subbuf_size - padding;
+ if (read_subbuf == write_subbuf) {
+ if (read_offset + padding < write_offset)
+ avail = write_offset - (read_offset + padding);
} else
- read_endpos = read_subbuf * subbuf_size + buf_offset;
+ avail = (subbuf_size - padding) - read_offset;
- return read_endpos;
+ return avail;
}
-/**
- * relayfs_read_avail - return total available along with buffer start
- *
- * Because buffers are circular, the 'beginning' of the buffer
- * depends on where the buffer was last written. If the writer
- * has cycled around the buffer, the beginning is defined to be
- * the beginning of the sub-buffer following the last sub-buffer
- * written to, otherwise it's the beginning of sub-buffer 0.
- *
- */
-static inline size_t relayfs_read_avail(struct rchan_buf *buf,
- size_t *start_subbuf)
+static void relayfs_read_consume(struct rchan_buf *buf,
+ size_t read_pos,
+ size_t bytes_consumed)
{
- size_t avail, complete_subbufs, cur_subbuf, buf_offset;
size_t subbuf_size = buf->chan->subbuf_size;
- size_t n_subbufs = buf->chan->n_subbufs;
+ size_t read_subbuf;
+ size_t tmp;
- buf_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
+ buf->bytes_consumed += bytes_consumed;
+ read_subbuf = read_pos / buf->chan->subbuf_size;
- if (buf->subbufs_produced >= n_subbufs) {
- complete_subbufs = n_subbufs - 1;
- cur_subbuf = (buf->data - buf->start) / subbuf_size;
- *start_subbuf = (cur_subbuf + 1) % n_subbufs;
- } else {
- complete_subbufs = buf->subbufs_produced;
- *start_subbuf = 0;
+ if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
+ tmp = buf->subbufs_consumed;
+ relay_subbufs_consumed(buf->chan, buf->cpu, 1);
+ if (buf->subbufs_consumed != tmp)
+ buf->bytes_consumed = 0;
}
-
- avail = complete_subbufs * subbuf_size + buf_offset;
-
- return avail;
}
/**
@@ -401,7 +380,7 @@
*
* Reads count bytes or the number of bytes available in the
* current sub-buffer being read, whichever is smaller.
- *
+ *
* NOTE: The results of reading a relayfs file which is currently
* being written to are undefined. This is because the buffer is
* circular and an active writer in the kernel could be
@@ -416,31 +395,40 @@
{
struct inode *inode = filp->f_dentry->d_inode;
struct rchan_buf *buf = RELAYFS_I(inode)->buf;
- size_t read_start, read_end, avail, start_subbuf;
- size_t buf_size = buf->chan->subbuf_size * buf->chan->n_subbufs;
+ size_t read_start, avail;
void *from;
+ long long produced, consumed;
+ size_t subbuf_size = buf->chan->subbuf_size;
+ size_t n_subbufs = buf->chan->n_subbufs;
+ size_t write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
- avail = relayfs_read_avail(buf, &start_subbuf);
- if (*ppos >= avail)
- return 0;
+ if (buf->offset > subbuf_size)
+ produced = (buf->subbufs_produced - 1) * subbuf_size + write_offset;
+ else
+ produced = buf->subbufs_produced * subbuf_size + write_offset;
+ consumed = buf->subbufs_consumed * subbuf_size + buf->bytes_consumed;
- read_start = relayfs_read_start(*ppos, avail, start_subbuf, buf);
- if (read_start == 0 && *ppos)
+ if (produced == consumed)
return 0;
- read_end = relayfs_read_end(read_start, avail, start_subbuf, buf);
- if (read_end == read_start)
- return 0;
+ relayfs_read_consume(buf, *ppos, 0);
- from = buf->start + start_subbuf * buf->chan->subbuf_size + read_start;
- if (from >= buf->start + buf_size)
- from -= buf_size;
+ read_start = relayfs_read_start(*ppos, buf);
- count = min(count, read_end - read_start);
+ avail = relayfs_read_avail(read_start, buf);
+ if (!avail)
+ return 0;
+
+ from = buf->start + read_start;
+ count = min(count, avail);
if (copy_to_user(buffer, from, count))
return -EFAULT;
*ppos = read_start + count;
+ if (*ppos >= subbuf_size * n_subbufs)
+ *ppos = 0;
+
+ relayfs_read_consume(buf, read_start, count);
return count;
}
--- linux-2.6.13-rc6-mm2/fs/relayfs/relay.c~ 2005-08-23 14:29:08.000000000 +0200
+++ linux-2.6.13-rc6-mm2/fs/relayfs/relay.c 2005-08-23 14:29:48.000000000 +0200
@@ -58,6 +58,14 @@
void *prev_subbuf,
size_t prev_padding)
{
+ if (relay_buf_full(buf)) {
+// if (smp_processor_id() == 0) {
+// printk("buf full, cpu %u\n", smp_processor_id());
+// klog_printk("buf full, cpu %u\n", smp_processor_id());
+// }
+ return 0;
+ }
+
return 1;
}
@@ -262,6 +270,7 @@
for_each_online_cpu(i) {
sprintf(tmpname, "%s%d", base_filename, i);
chan->buf[i] = relay_open_buf(chan, tmpname, parent);
+ chan->buf[i]->cpu = i;
if (!chan->buf[i])
goto free_bufs;
}
@@ -328,7 +337,7 @@
return length;
toobig:
- printk(KERN_WARNING "relayfs: event too large (%u)\n", length);
+ printk(KERN_WARNING "relayfs: event too large (%lu)\n", length);
WARN_ON(1);
return 0;
}
--- linux-2.6.13-rc6-mm2/include/linux/relayfs_fs.h~ 2005-08-23 14:29:21.000000000 +0200
+++ linux-2.6.13-rc6-mm2/include/linux/relayfs_fs.h 2005-08-23 14:29:31.000000000 +0200
@@ -22,7 +22,7 @@
/*
* Tracks changes to rchan_buf struct
*/
-#define RELAYFS_CHANNEL_VERSION 4
+#define RELAYFS_CHANNEL_VERSION 5
/*
* Per-cpu relay channel buffer
@@ -44,6 +44,8 @@
unsigned int finalized; /* buffer has been finalized */
size_t *padding; /* padding counts per sub-buffer */
size_t prev_padding; /* temporary variable */
+ size_t bytes_consumed; /* bytes consumed in cur read subbuf */
+ unsigned int cpu; /* this buf's cpu */
} ____cacheline_aligned;
/*