linux-kernel - Re: [PATCH 5/5] blktrace: print human-readable act

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Message-ID: <49C8A166.8050303@cn.fujitsu.com>
Date:	Tue, 24 Mar 2009 17:01:26 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Jens Axboe <jens.axboe@...cle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/5] blktrace: print human-readable act_mask

Ingo Molnar wrote:
> * Li Zefan <lizf@...fujitsu.com> wrote:
> 
>> Print stringified act_mask instead of hex value:
>>  # cat act_mask
>>  read,write,barrier,sync,queue,requeue,issue,complete,fs,pc,ahead,meta,
>>  discard,drv_data
>>  # echo "meta,write" > act_mask
>>  # cat act_mask
>>  write,meta
> 
> Nice!
> 
> It would also be nice to activate trace filters for the blktrace 
> tracepoints - i.e. to convert them to the TRACE_EVENT() enumeration 
> format. Beyond user-space parseable field enumeration and filter, 
> that will also speed up tracing and allows binary record streaming 
> with splice() zero-copy.
> 
> Via that "act_mask" can become a filterable field and you can define 
> expressions to filter. All other fields like sector become in-kernel 
> filterable too.
> 
> See a few examples here:
> 
>  include/trace/irq_event_types.h
>  include/trace/sched_event_types.h
> 
> Note, blktrace tracepoints are certainly more complex than the 
> tracepoints above - you can embedd C statements in TRACE_EVENT()'s 
> TP_fast_assign() bit.
> 
> It was specifically designed to allow the support of blktrace 
> tracepoints, so you can embedd the blk_pc_request() and disk_devt() 
> translation for the block_rq_complete event or 
> block_rq_requeue/issue tracepoints.
> 

I'll look into this when I have time. :)
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