On Sat, Nov 19 2016, Shaohua Li wrote:
> On Fri, Nov 18, 2016 at 09:26:22AM -0800, Shaohua Li wrote:
>> On Fri, Nov 18, 2016 at 01:22:04PM +1100, Neil Brown wrote:
>> >
>> > The block tracing infrastructure (accessed with blktrace/blkparse)
>> > supports the tracing of mapping bios from one device to another.
>> > This is currently used when a bio in a partition is mapped to the
>> > whole device, when bios are mapped by dm, and for mapping in md/raid5.
>> > Other md personalities do not include this tracing yet, so add it.
>> >
>> > When a read-error is detected we redirect the request to a different device.
>> > This could justifiably be seen as a new mapping for the originial bio,
>> > or a secondary mapping for the bio that errors. This patch uses
>> > the second option.
>> >
>> > When md is used under dm-raid, the mappings are not traced as we do
>> > not have access to the block device number of the parent.
>>
>> thanks, applied patch 1, 3, 4.
>
> BTW, I added below patch
>
Yes, that looks good. Thanks!
NeilBrown
>
> commit 504634f60f463e73e7d58c6810a04437da942dba
> Author: Shaohua Li <shli@xxxxxx>
> Date: Fri Nov 18 09:44:08 2016 -0800
>
> md: add blktrace event for writes to superblock
>
> superblock write is an expensive operation. With raid5-cache, it can be called
> regularly. Tracing to help performance debug.
>
> Signed-off-by: Shaohua Li <shli@xxxxxx>
> Cc: NeilBrown <neilb@xxxxxxxx>
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 1f1c7f0..d3cef77 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -64,6 +64,7 @@
> #include <linux/raid/md_p.h>
> #include <linux/raid/md_u.h>
> #include <linux/slab.h>
> +#include <trace/events/block.h>
> #include "md.h"
> #include "bitmap.h"
> #include "md-cluster.h"
> @@ -2403,6 +2404,8 @@ void md_update_sb(struct mddev *mddev, int force_change)
> pr_debug("md: updating %s RAID superblock on device (in sync %d)\n",
> mdname(mddev), mddev->in_sync);
>
> + if (mddev->queue)
> + blk_add_trace_msg(mddev->queue, "md md_update_sb");
> bitmap_update_sb(mddev->bitmap);
> rdev_for_each(rdev, mddev) {
> char b[BDEVNAME_SIZE];
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