linux-kernel - Re: [PATCH v2 1/5] perf probe: Split add_perf_probe

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Date:	Thu, 10 Sep 2015 11:23:25 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	"Wangnan (F)" <wangnan0@...wei.com>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Jiri Olsa <jolsa@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	pi3orama@....com
Subject: Re: [PATCH v2 1/5] perf probe: Split add_perf_probe_events()

On Sun, Sep 06, 2015 at 03:47:37PM +0800, Wangnan (F) wrote:
> Hi Namhyung,

Hi,

> 
> Thanks for this patchset.
> 
> Could you plase have a look at patch 5/27 and 6/27 in my newest pull
> request?
> These 2 patches utilize new probing API to create probe point and collect
> probe_trace_events. I'm not very sure I fully understand your design
> principle,
> especially the cleanup part, because I can see different functions dealing
> with
> cleanup:
> 
> cleanup_perf_probe_events
> del_perf_probe_events
> clear_perf_probe_event
> clear_probe_trace_event
> 
> But non of them works perfectly for me.

The cleanup_perf_probe_events() is just to keep the existing logic as
long as possible.  But I think it needs to call
clear_perf_probe_event().

The del_perf_probe_events() uses strfilter, but I think it can be
problematic if other instances or users are using similar events at
the same time.

So for your case, IMHO it'd better keeping the perf/trace events after
probing and reusing the events for unprobing.  I'll take a look at it.


> 
> In bpf_prog_priv__clear() function of 6/27, I copied some code from
> cleanup_perf_probe_events(), because I think when destroying bpf programs,
> the probe_trace_events should also be cleanuped, but we don't need call
> exit_symbol_maps() many times, because we are in 'perf record', and not
> sure whether other parts of perf need symbol maps. Otherwise I think
> directly
> calling cleanup_perf_probe_events() sould be better.

Yeah, I also think exit_symbol_maps() should not be a part of the
cleanup.  I'll send a patch soon.


> 
> You can find patch from:
> 
> http://lkml.kernel.org/n/1441523623-152703-6-git-send-email-wangnan0@huawei.com
> 
> http://lkml.kernel.org/n/1441523623-152703-7-git-send-email-wangnan0@huawei.com

Thanks for your work!
Namhyung
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