linux-kernel - Re: [PATCH 03/11] tracing: add soft disable for syscall events

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Date:	Sat, 22 Jun 2013 07:45:23 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Jovi Zhang <bookjovi@...il.com>
Cc:	"zhangwei(Jovi)" <jovi.zhangwei@...wei.com>,
	Tom Zanussi <tom.zanussi@...ux.intel.com>,
	masami.hiramatsu.pt@...achi.com,
	LKML <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH 03/11] tracing: add soft disable for syscall events

On Sat, 2013-06-22 at 13:08 +0800, Jovi Zhang wrote:

> > I would really like to make these smaller. They are made for every
> > system call, and I consider tracing to always be added overhead. I hate
> > it when we waste more memory for tracing as very few people use it
> > (compared to those that use Linux).
> >
> > Is it possible to allocate this only when its first used?
> >
> > -- Steve
> 
> I think the answer is yes.
> 
> Compare with link ftrace_event_file with static syscall_metadata, another option
> is put into structure trace_array, just like enabled_enter_syscalls and
> enabled_exit_syscalls BITMAP already in there
> (need change to dynamic allocated NR_syscalls array, just keep a
> pointer in trace_array).
> 
> Then in this way, there don't have any extra size overhead for static
> syscall_metadata,
> but need to allocate a array with NR_syscalls elements when first use
> syscall tracing.
> 
> which option do you prefer? steven.

Hey, if it only allocates when tracing is used, that's a big plus.
Tracing should be treated as a drug. Just like not allowing smoking in
public places, only punish the users, not those that want to breath
fresh air.

-- Steve


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