Re: [RFC] blktrace interface for sg devices
On Thu, Dec 13, 2007 at 10:19:42AM +0100, Jens Axboe wrote:
[...]
> I think this approach is the simplest and right way to do it. Tracing is
> really just tied to the "transport" (transport here meaning how we
> transport commands to the device), and even character scsi devices use
> the block layer queue for this operation, as you note.
>
> Let me know when you are happy with the patch, and I'll queue it up for
> 2.6.25.
> > @@ -1066,6 +1068,16 @@ sg_ioctl(struct inode *inode, struct fil
> > case BLKSECTGET:
> > return put_user(sdp->device->request_queue->max_sectors * 512,
> > ip);
> > + case BLKTRACESETUP:
> > + {
> > + return blk_trace_setup(sdp->device->request_queue ,
> > sdp->device->sdev_gendev.bus_id, &sdp->device->sdev_gendev, arg);
> > + }
>
> Don't need those braces, some other space and long line style issues as
> well.
>
> > --- a/include/linux/blkdev.h2007-12-13 08:48:23.0 +0100
> > +++ b/include/linux/blkdev.h2007-12-13 08:48:25.0 +0100
> > @@ -747,6 +747,16 @@ static inline void blkdev_dequeue_reques
> > elv_dequeue_request(req->q, req);
> > }
> >
> > +#ifdef CONFIG_BLK_DEV_IO_TRACE
> > +extern int blk_trace_setup(request_queue_t *q, char * name, dev_t dev,
> > char __user *arg);
> > +extern int blk_trace_startstop(request_queue_t *q, int start);
> > +extern int blk_trace_remove(request_queue_t *q);
> > +#else
> > +#define blk_trace_setup(q, name, dev, arg) do { } while(0)
> > +#define blk_trace_startstop(q, start) do { } while(0)
> > +#define blk_trace_remove(q) do { } while(0)
> > +#endif
> > +
>
> Put these in the blktrace include file.
Thanks for your input. I will prepare and send an updated version of
the patch. I also want to do some more testing, especially to see how
i can get the sizes of read and write requests and latencies for SCSI
tape drives.
Christof Schmitt
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Re: [RFC] blktrace interface for sg devices
On Thu, Dec 13 2007, Christof Schmitt wrote:
> I am referring to the discussion of introducing statistics in the SCSI
> layer and the conclusion that blktrace already provides the data:
> http://lkml.org/lkml/2006/10/21/72
> http://lkml.org/lkml/2006/11/2/141
>
> While blktrace works fine for disk devices, it currently does not
> provide data for non-disk devices like tape drives. To close this gap,
> i am looking for a way to get the same trace data also from other SCSI
> devices.
>
> Since the SCSI layer internally uses the same request queuest for all
> devices and the queues already use the blktrace interface, the main
> missing part is the interface to enable the tracing for all SCSI
> devices.
>
> Attached is a patch that adds the ioctl interface for blktrace to the
> sg generic scsi interface. This already allows to get some trace data
> for SCSI tape drives, although i have to do more testing.
>
> For testing, any sg device file can be passed to blktrace, e.g.:
> # blktrace -d /dev/sg1 -o - | blkparse -i -
>
> I am seeking input in this approach: Is this approach worth pursuing
> to enable blktrace to trace SCSI tape drives? Would there be a better
> approach to get this trace data?
I think this approach is the simplest and right way to do it. Tracing is
really just tied to the "transport" (transport here meaning how we
transport commands to the device), and even character scsi devices use
the block layer queue for this operation, as you note.
Let me know when you are happy with the patch, and I'll queue it up for
2.6.25.
> @@ -1066,6 +1068,16 @@ sg_ioctl(struct inode *inode, struct fil
> case BLKSECTGET:
> return put_user(sdp->device->request_queue->max_sectors * 512,
> ip);
> + case BLKTRACESETUP:
> + {
> + return blk_trace_setup(sdp->device->request_queue ,
> sdp->device->sdev_gendev.bus_id, &sdp->device->sdev_gendev, arg);
> + }
Don't need those braces, some other space and long line style issues as
well.
> --- a/include/linux/blkdev.h 2007-12-13 08:48:23.0 +0100
> +++ b/include/linux/blkdev.h 2007-12-13 08:48:25.0 +0100
> @@ -747,6 +747,16 @@ static inline void blkdev_dequeue_reques
> elv_dequeue_request(req->q, req);
> }
>
> +#ifdef CONFIG_BLK_DEV_IO_TRACE
> +extern int blk_trace_setup(request_queue_t *q, char * name, dev_t dev, char
> __user *arg);
> +extern int blk_trace_startstop(request_queue_t *q, int start);
> +extern int blk_trace_remove(request_queue_t *q);
> +#else
> +#define blk_trace_setup(q, name, dev, arg) do { } while(0)
> +#define blk_trace_startstop(q, start) do { } while(0)
> +#define blk_trace_remove(q) do { } while(0)
> +#endif
> +
Put these in the blktrace include file.
--
Jens Axboe
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[RFC] blktrace interface for sg devices
I am referring to the discussion of introducing statistics in the SCSI
layer and the conclusion that blktrace already provides the data:
http://lkml.org/lkml/2006/10/21/72
http://lkml.org/lkml/2006/11/2/141
While blktrace works fine for disk devices, it currently does not
provide data for non-disk devices like tape drives. To close this gap,
i am looking for a way to get the same trace data also from other SCSI
devices.
Since the SCSI layer internally uses the same request queuest for all
devices and the queues already use the blktrace interface, the main
missing part is the interface to enable the tracing for all SCSI
devices.
Attached is a patch that adds the ioctl interface for blktrace to the
sg generic scsi interface. This already allows to get some trace data
for SCSI tape drives, although i have to do more testing.
For testing, any sg device file can be passed to blktrace, e.g.:
# blktrace -d /dev/sg1 -o - | blkparse -i -
I am seeking input in this approach: Is this approach worth pursuing
to enable blktrace to trace SCSI tape drives? Would there be a better
approach to get this trace data?
Christof Schmitt
---
block/blktrace.c | 19 +++
drivers/scsi/sg.c | 12
include/linux/blkdev.h | 10 ++
3 files changed, 33 insertions(+), 8 deletions(-)
--- a/block/blktrace.c 2007-12-13 08:48:23.0 +0100
+++ b/block/blktrace.c 2007-12-13 08:48:25.0 +0100
@@ -231,7 +231,7 @@ static void blk_trace_cleanup(struct blk
kfree(bt);
}
-static int blk_trace_remove(struct request_queue *q)
+int blk_trace_remove(struct request_queue *q)
{
struct blk_trace *bt;
@@ -245,6 +245,7 @@ static int blk_trace_remove(struct reque
return 0;
}
+EXPORT_SYMBOL_GPL(blk_trace_remove);
static int blk_dropped_open(struct inode *inode, struct file *filp)
{
@@ -312,13 +313,11 @@ static struct rchan_callbacks blk_relay_
/*
* Setup everything required to start tracing
*/
-static int blk_trace_setup(struct request_queue *q, struct block_device *bdev,
- char __user *arg)
+int blk_trace_setup(struct request_queue *q, char *name, dev_t dev, 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)))
@@ -327,7 +326,7 @@ static int blk_trace_setup(struct reques
if (!buts.buf_size || !buts.buf_nr)
return -EINVAL;
- strcpy(buts.name, bdevname(bdev, b));
+ strcpy(buts.name, name);
/*
* some device names have larger paths - convert the slashes
@@ -355,7 +354,7 @@ static int blk_trace_setup(struct reques
goto err;
bt->dir = dir;
- bt->dev = bdev->bd_dev;
+ bt->dev = dev;
atomic_set(&bt->dropped, 0);
ret = -EIO;
@@ -400,8 +399,9 @@ err:
}
return ret;
}
+EXPORT_SYMBOL_GPL(blk_trace_setup);
-static int blk_trace_startstop(struct request_queue *q, int start)
+int blk_trace_startstop(struct request_queue *q, int start)
{
struct blk_trace *bt;
int ret;
@@ -434,6 +434,7 @@ static int blk_trace_startstop(struct re
return ret;
}
+EXPORT_SYMBOL_GPL(blk_trace_startstop);
/**
* blk_trace_ioctl: - handle the ioctls associated with tracing
@@ -446,6 +447,7 @@ int blk_trace_ioctl(struct block_device
{
struct request_queue *q;
int ret, start = 0;
+ char b[BDEVNAME_SIZE];
q = bdev_get_queue(bdev);
if (!q)
@@ -455,7 +457,8 @@ int blk_trace_ioctl(struct block_device
switch (cmd) {
case BLKTRACESETUP:
- ret = blk_trace_setup(q, bdev, arg);
+ strcpy(b, bdevname(bdev, b));
+ ret = blk_trace_setup(q, b, bdev->bd_dev, arg);
break;
case BLKTRACESTART:
start = 1;
--- a/drivers/scsi/sg.c 2007-12-13 08:48:23.0 +0100
+++ b/drivers/scsi/sg.c 2007-12-13 08:48:25.0 +0100
@@ -55,6 +55,8 @@ static int sg_version_num = 30534;/* 2
#include
#include
+#include
+
#include "scsi_logging.h"
#ifdef CONFIG_SCSI_PROC_FS
@@ -1066,6 +1068,16 @@ sg_ioctl(struct inode *inode, struct fil
case BLKSECTGET:
return put_user(sdp->device->request_queue->max_sectors * 512,
ip);
+ case BLKTRACESETUP:
+ {
+ return blk_trace_setup(sdp->device->request_queue ,
sdp->device->sdev_gendev.bus_id, &sdp->device->sdev_gendev, arg);
+ }
+ case BLKTRACESTART:
+ return blk_trace_startstop(sdp->device->request_queue, 1);
+ case BLKTRACESTOP:
+ return blk_trace_startstop(sdp->device->request_queue, 0);
+ case BLKTRACETEARDOWN:
+ return blk_trace_remove(sdp->device->request_queue);
default:
