linux-kernel - Re: [PATCH 2/2] drm/ttm: Use pr_debug for all output from ttm_bo

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Date:   Thu, 6 Dec 2018 10:50:29 +0100
From:   Michel Dänzer <michel@...nzer.net>
To:     "Koenig, Christian" <Christian.Koenig@....com>,
        "Zhang, Jerry" <Jerry.Zhang@....com>,
        "Huang, Ray" <Ray.Huang@....com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH 2/2] drm/ttm: Use pr_debug for all output from
 ttm_bo_evict

On 2018-12-06 10:38 a.m., Michel Dänzer wrote:
> On 2018-12-06 10:33 a.m., Koenig, Christian wrote:
>> Am 06.12.18 um 10:09 schrieb Michel Dänzer:
>>> On 2018-12-06 3:43 a.m., Zhang, Jerry(Junwei) wrote:
>>>> On 12/6/18 12:56 AM, Michel Dänzer wrote:
>>>>> From: Michel Dänzer <michel.daenzer@....com>
>>>>>
>>>>> All the output is related, so it should all be printed the same way.
>>>>> Some of it was using pr_debug, but some of it appeared in dmesg by
>>>>> default. The caller should handle failure, so there's no need to spam
>>>>> dmesg with potentially quite a lot of output by default.
>>>>>
>>>>> Signed-off-by: Michel Dänzer <michel.daenzer@....com>
>>>> Sounds reasonable, but personally prefer to show error when some
>>>> vital incident happens, e.g. no memory on eviction.
>>> The amdgpu driver still prints these in that case:
>>>
>>>   [drm:amdgpu_cs_ioctl [amdgpu]] *ERROR* amdgpu_cs_list_validate(validated) failed.
>>>   [drm:amdgpu_cs_ioctl [amdgpu]] *ERROR* Not enough memory for command submission!
>>>
>>> That's plenty as far as I'm concerned. :)
>>
>> Yeah, but in this case I would rather make the amdgpu messages debug 
>> level and leave the TTM meassages on error level.
> 
> That makes no sense to me.
> 
> The amdgpu messages have some value for normal users / bug reports,
> indicating that something isn't going quite as planned.
> 
> The TTM messages are orders of magnitude longer, and are basically noise
> for a normal user.
> 
> Seems like a no-brainer to me which of these should be visible by default.

Moreover, not every case producing the driver output also produces the
TTM output, so it could make it difficult to realize that there's a
memory pressure situation.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer