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Date: Fri, 25 Jan 2013 20:34:07 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>, Ingo Molnar <mingo@elte.hu>,
        Anton Arapov <anton@redhat.com>, Christoph Hellwig <hch@infradead.org>,
        Josh Stone <jistone@redhat.com>, linux-kernel@vger.kernel.org,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Suzuki Poulose <suzuki@in.ibm.com>,
        Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Subject: Re: [GIT PULL] uprobes: pre-filtering
Message-ID: <20130125193407.GA20075@redhat.com>
References: <20130113185916.GA25831@redhat.com> <20130124121720.GA3104@gmail.com> <20130124154018.GA8580@redhat.com> <20130124154159.GB32071@gmail.com> <20130124170612.GA14823@redhat.com> <20130125064629.GD23723@linux.vnet.ibm.com> <20130125075437.GB21036@gmail.com> <20130125161728.GA11630@redhat.com> <20130125184602.GD31022@gmail.com>
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On 01/25, Ingo Molnar wrote:
>
> * Oleg Nesterov <oleg@redhat.com> wrote:
>
> > On 01/25, Ingo Molnar wrote:
> > >
> > > * Srikar Dronamraju <srikar@linux.vnet.ibm.com> wrote:
> > >
> > > > The other alternative is to extend the current abi and pass
> > > > the prefilter option. Should we extend the abi for userspace
> > > > tracing is obviously debatable.
> > >
> > > That's the obvious path to go - why add something to the kernel
> > > if user-space cannot make use of it?
> >
> > This is what I am going to (try to) do, but I am not sure if this makes
> > sense...
> >
> > For the start, can't we teach 'uprobe_events' file to accept, say,
> >
> > 	'p file:0x1234 pid=1 other-opts'
> >
> > for the start? This looks simple enough, and I after looked
> > into tools/perf it seems that perf can be changed too.
> >
> > What do you think?
>
> Sounds sensible and functional to me.

Great, thanks.

> > Then we can extend 'pid=' option to accept the list of pids,
> > perhaps.
> >
> > In the long term we probably need uprobes/pid_filter or
> > something like this, it should allow to add/del pid
> > dynamically. I really do not know.
>
> For now removing+adding a new one should be enough to 'change' a
> uprobe, right?

Yes, yes. I meant that obviously we can do more/better to filter-out
the tasks we do not want to probe. But this need more changes, and more
importantly this needs more discussion about API/ABI/etc.

Thanks.

Oleg.