Return-path: Received: from mail-wm0-f47.google.com ([74.125.82.47]:36802 "EHLO mail-wm0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751062AbdEaV2m (ORCPT ); Wed, 31 May 2017 17:28:42 -0400 Received: by mail-wm0-f47.google.com with SMTP id 7so134251888wmo.1 for ; Wed, 31 May 2017 14:28:41 -0700 (PDT) Subject: Re: [PATCH] ath10k: add configurable debugging. To: Adrian Chadd Cc: Kalle Valo , "ath10k@lists.infradead.org" , "linux-wireless@vger.kernel.org" References: <20170510211925.17468-1-adrian@freebsd.org> <87y3tdmdbo.fsf@kamboji.qca.qualcomm.com> <2a6a2af2-29c7-6b74-ead1-c5ae8688a87c@broadcom.com> From: Arend van Spriel Message-ID: (sfid-20170531_232846_024670_05B58B5A) Date: Wed, 31 May 2017 23:28:39 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: On 31-05-17 22:23, Adrian Chadd wrote: > On 31 May 2017 at 13:20, Arend van Spriel wrote: >> On 31-05-17 14:16, Kalle Valo wrote: >>> Adrian Chadd writes: >>> >>>> This adds a few configurable debugging options: >>>> >>>> * driver debugging and tracing is now configurable per device >>>> * driver debugging and tracing is now configurable at runtime >>>> * the debugging / tracing is not run at all (besides a mask check) >>>> unless the specific debugging bitmap field is configured. >>>> >>>> Signed-off-by: Adrian Chadd >>> >>> [...] >>> >>>> --- a/drivers/net/wireless/ath/ath10k/core.c >>>> +++ b/drivers/net/wireless/ath/ath10k/core.c >>>> @@ -2444,6 +2444,8 @@ struct ath10k *ath10k_core_create(size_t priv_size, struct device *dev, >>>> ar->hw_rev = hw_rev; >>>> ar->hif.ops = hif_ops; >>>> ar->hif.bus = bus; >>>> + ar->debug_mask = ath10k_debug_mask; >>>> + ar->trace_debug_mask = ath10k_debug_mask; >>> >>> Until now tracing has been always enabled, irrespective what debug_mask >>> has contained. Now you are changing that and by default log messages are >>> not delivered through tracing until user enables them. So I think to >>> keep the old behaviour trace_debug_mask should be ATH10K_DBG_ANY >>> (0xffffffff) by default and the user can modify the mask per device via >>> the debugfs file. >>> >>> But is it really needed to be able to filter trace messages? debug_mask >>> I understand, but not sure about trace_debug_mask. >> >> FWIW, in brcmfmac I decided not to filter trace messages. The overhead >> is relatively small and if needed you can pass filter expressions with >> trace-cmd record. > > The reason for configuring it via a mask is that: > > * the previous behaviour is "always call debug(), conditionally print, > always pass to trace" > > This meant that function arguments were evaluated even if things > weren't being printed. > > So to avoid that in the default case, there are now two masks. If I > have one mask then I can only trace what is being printed, which is > not desired. I'd like to be able to have no overhead when doing no > debugging, a little overhead when doing tracing (and only the items > being traced), and then printing when I want to print. Well, it is up to you. Have to clariy though that if you are not actually recording a trace there is (almost) no overhead. We have Kconfig to compile tracing code in and I see no performance impact with tracing code. Only when doing tracing you will get little overhead. Regards, Arend > -adrian >