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

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Message-ID: <30a65cd2-6dda-4459-82bb-cf0d449f5754@daenzer.net>
Date:   Thu, 6 Dec 2018 18:28:39 +0100
From:   Michel Dänzer <michel@...nzer.net>
To:     Joe Perches <joe@...ches.com>,
        "Zhang, Jerry(Junwei)" <Jerry.Zhang@....com>,
        "Koenig, Christian" <Christian.Koenig@....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 5:46 p.m., Joe Perches wrote:
> On Thu, 2018-12-06 at 17:39 +0800, Zhang, Jerry(Junwei) wrote:
>> On 12/6/18 5:33 PM, 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!
> 
> Aren't dump_stack()s already done on all these allocation failures?
> I don't notice any use of __GFP_NOWARN on generic allocations in drm.

Most of the time, these messages are due to being unable to allocate a
TTM BO or move it where it needs to go, not due to the kernel failing to
allocate memory in general.


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