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Date: Wed, 19 Jan 2011 08:06:43 -0700
From: Jens Axboe <axboe@...nel.dk>
To: Jeff Moyer <jmoyer@...hat.com>
CC: Tao Ma <tm@....ma>, linux-kernel@...r.kernel.org,
Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH v2] blktrace: Don't output messages if NOTIFY isn't set.
On 2011-01-19 08:04, Jeff Moyer wrote:
> Jens Axboe <axboe@...nel.dk> writes:
>
>> On 2011-01-18 23:09, Tao Ma wrote:
>>> On 01/19/2011 01:36 PM, Jens Axboe wrote:
>>>> On 2011-01-18 20:09, Tao Ma wrote:
>>>>> Hi Jeff,
>>>>> On 01/18/2011 11:50 PM, Jeff Moyer wrote:
>>>>>> Tao Ma<tm@....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@...bao.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@...nel.dk>
>>>>> Cc: Steven Rostedt<rostedt@...dmis.org>
>>>>> Cc: Jeff Moyer<jmoyer@...hat.com>
>>>>> Signed-off-by: Tao Ma<boyu.mt@...bao.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.
>>> uh, yes, that's the reason why I put the check in __trace_note_message,
>>> not in trace_note. trace_note_time and trace_note_tsk will handle
>>> time/task issue and then call trace_note with the appropriate action
>>> mask. Do I miss something here?
>>
>> You did, I missed that. Patch looks fine then, I'll queue it up. Thanks!
>
> I was guessing at the use of BLK_TC_NOTIFY for this. Should there be
> another flag for these messages, so they aren't conflated with
> task/timestamp notifications?
The correct check for just a message would be:
__BLK_TN_MESSAGE | BLK_TC_ACT(BLK_TC_NOTIFY)
--
Jens Axboe
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