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SubjectRe: [PATCH v2] blktrace: Don't output messages if NOTIFY isn't set.
On 2011-01-18 20:09, Tao Ma wrote:
> Hi Jeff,
> On 01/18/2011 11:50 PM, Jeff Moyer wrote:
>> Tao Ma<tm@tao.ma> writes:
>>
>>> + /*
>>> + * If the user does specify some action masks, don't send any note
>>> + * message to the trace so that it won't pollute what the user really
>>> + * want to see.
>>> + */
>>> + if (bt->act_mask != (u16) -1)
>>> + return;
>>> +
>>
>> I think you want to check for the BLK_TC_NOTIFY bit.
> I was thinking of this, but actually there is no way for the user to set this flag.
> At least from blktrace(8), -a doesn't have any flags like NOTIFY. So if the user
> set any flag, NOTIFY will be cleared. So it does work. Thanks.
>
> Here is the updated patch.
>
> From 8693c19f165b09f60d5c26aed369d79a79e144ba Mon Sep 17 00:00:00 2001
> From: Tao Ma <boyu.mt@taobao.com>
> Date: Wed, 19 Jan 2011 10:51:44 +0800
> Subject: [PATCH v2] blktrace: Don't output messages if NOTIFY isn't set.
>
> Now if we enable blktrace, cfq has too many messages output to the
> trace buffer. It is fine if we don't specify any action mask.
> But if I do like this:
> blktrace /dev/sdb -a issue -a complete -o - | blkparse -i -
> I only want to see 'D' and 'C', while with the following command
> dd if=/mnt/ocfs2/test of=/dev/null bs=4k count=1 iflag=direct
>
> I will get(with a 2.6.37 vanilla kernel):
> 8,16 0 0 0.000000000 0 m N cfq3805 alloced
> 8,16 0 0 0.000004126 0 m N cfq3805 insert_request
> 8,16 0 0 0.000004884 0 m N cfq3805 add_to_rr
> 8,16 0 0 0.000008417 0 m N cfq workload slice:300
> 8,16 0 0 0.000009557 0 m N cfq3805 set_active wl_prio:0 wl_type:2
> 8,16 0 0 0.000010640 0 m N cfq3805 fifo= (null)
> 8,16 0 0 0.000011193 0 m N cfq3805 dispatch_insert
> 8,16 0 0 0.000012221 0 m N cfq3805 dispatched a request
> 8,16 0 0 0.000012802 0 m N cfq3805 activate rq, drv=1
> 8,16 0 1 0.000013181 3805 D R 114759 + 8 [dd]
> 8,16 0 2 0.000164244 0 C R 114759 + 8 [0]
> 8,16 0 0 0.000167997 0 m N cfq3805 complete rqnoidle 0
> 8,16 0 0 0.000168782 0 m N cfq3805 set_slice=100
> 8,16 0 0 0.000169874 0 m N cfq3805 arm_idle: 8 group_idle: 0
> 8,16 0 0 0.000170189 0 m N cfq schedule dispatch
> 8,16 0 0 0.000397938 0 m N cfq3805 slice expired t=0
> 8,16 0 0 0.000399763 0 m N cfq3805 sl_used=1 disp=1 charge=1 iops=0 sect=8
> 8,16 0 0 0.000400227 0 m N cfq3805 del_from_rr
> 8,16 0 0 0.000400882 0 m N cfq3805 put_queue
>
> See, there are 19 lines while I only need 2. I don't think it is
> appropriate for a user.
>
> So this patch will disable any messages if the BLK_TC_NOTIFY isn't set.
> Now the output for the same command will look like:
> 8,16 0 1 0.000000000 4908 D R 114759 + 8 [dd]
> 8,16 0 2 0.000146827 0 C R 114759 + 8 [0]
>
> Yes, it is what I want to see.
>
> Cc: Jens Axboe <axboe@kernel.dk>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Jeff Moyer <jmoyer@redhat.com>
> Signed-off-by: Tao Ma <boyu.mt@taobao.com>
> ---
> kernel/trace/blktrace.c | 7 +++++++
> 1 files changed, 7 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
> index 153562d..d95721f 100644
> --- a/kernel/trace/blktrace.c
> +++ b/kernel/trace/blktrace.c
> @@ -138,6 +138,13 @@ void __trace_note_message(struct blk_trace *bt, const char *fmt, ...)
> !blk_tracer_enabled))
> return;
>
> + /*
> + * If the BLK_TC_NOTIFY action mask isn't set, don't send any note
> + * message to the trace.
> + */
> + if (!(bt->act_mask & BLK_TC_NOTIFY))
> + return;
> +
> local_irq_save(flags);
> buf = per_cpu_ptr(bt->msg_data, smp_processor_id());
> va_start(args, fmt);

Hmm, it should only mask messages, not task/timestamp notifies. This
will mask all of them.

The message mask I agree with, but the other ones should essentially be
unmaskable.

--
Jens Axboe



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