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Message-ID: <4D36FFB2.8090303@tao.ma> Date: Wed, 19 Jan 2011 23:13:54 +0800 From: Tao Ma <tm@....ma> To: Jeff Moyer <jmoyer@...hat.com> CC: Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org Subject: Re: [PATCH v2] blktrace: Don't output messages if NOTIFY isn't set. On 01/19/2011 11:04 PM, 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? I was thinking of this and gave up. Now we already have 15 different TC_FLAGS(yes, barrier may be removed, but for the compatibility problem, it have to stay there for some time I guess). and it seems we can have 16 flags totally(in blk_io_trace we have a u32 for action and the high 16 bit are used for TC_FLAGS). So I guess a new flag isn't suitable here. Regards, Tao -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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