Re: 答复: [External Mail]Re: [PATCH v4] dma-buf: add some tracepoints to debug.

["Christian König" <christian.koenig@amd.com>]

On 12/1/25 02:44, 高翔 wrote:
>> BTW We don't have any identification for an attachment, so when multiple devices attach to the same DMA-buf the trace would be quite meaningless. We should probably fix that.
> At present, from the perspective of processes, trace still makes sense.

Yeah, it probably do in most use cases. I just want to cover all use cases.

Maybe just use %p to print the attachment pointer until we have something better.

> 
> ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> *发件人:* 高翔
> *发送时间:* 2025年11月28日 21:14:14
> *收件人:* Christian König; Barry Song; Xiang Gao
> *抄送:* sumit.semwal@linaro.org; rostedt@goodmis.org; mhiramat@kernel.org; linux-media@vger.kernel.org; dri-devel@lists.freedesktop.org; linux-kernel@vger.kernel.org; mathieu.desnoyers@efficios.com; dhowells@redhat.com; kuba@kernel.org; brauner@kernel.org; akpm@linux-foundation.org; linux-trace-kernel@vger.kernel.org
> *主题:* 答复: [External Mail]Re: [PATCH v4] dma-buf: add some tracepoints to debug.
>  
> 
>> Thinking more about it I was wondering if we really need the userspace assigned name in the tracepoint in the first place.
>> The ino should be sufficient to uniquely identify each dma-buf, tracing the name should only be printed if it's changing or otherwise we spam the tracelog quite a bit with it.
> 
> Many threads use dmabuf "qcom,system". If there is a userspace name, we can immediately find the dmabuf I'm using. It might indeed not be necessary in other scenarios.

The DMA-buf "name" is an userspace assigned name and *not* useable for what you suggest here.

E.g. it is usually something like "texture", "shader", "dummy", "global"....

Could be that you have a driver or use case where it is something more specific and we can keep it where it makes sense for you, but I strongly suggest to always print the ino first since that one is guaranteed to be unique.

Regards,
Christian.

> 
> 
>> BTW We don't have any identification for an attachment, so when multiple devices attach to the same DMA-buf the trace would be quite meaningless. We should probably fix that.
> 
> This requires some thought.
> 
> ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> *发件人:* Christian König <christian.koenig@amd.com>
> *发送时间:* 2025年11月28日 17:39:31
> *收件人:* Barry Song; Xiang Gao
> *抄送:* sumit.semwal@linaro.org; rostedt@goodmis.org; mhiramat@kernel.org; linux-media@vger.kernel.org; dri-devel@lists.freedesktop.org; linux-kernel@vger.kernel.org; mathieu.desnoyers@efficios.com; dhowells@redhat.com; kuba@kernel.org; brauner@kernel.org; akpm@linux-foundation.org; linux-trace-kernel@vger.kernel.org; 高翔
> *主题:* [External Mail]Re: [PATCH v4] dma-buf: add some tracepoints to debug.
>  
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> 
> On 11/28/25 10:31, Barry Song wrote:
>> On Fri, Nov 28, 2025 at 4:53 PM Xiang Gao <gxxa03070307@gmail.com> wrote:
>>>
>>> From: gaoxiang17 <gaoxiang17@xiaomi.com>
>>>
>>> I want to track the status of dmabuf in real time in the production environment.
>>> But now we can only check it by traversing the fd in the process or dmabuf_list.
>>
>> might be:
>>
>> Since we can only inspect dmabuf by iterating over process FDs or the
>> dmabuf_list, we need to add our own tracepoints to track its status in
>> real time in production.
>>
>>>
>>> For example:
>>>    binder:3031_4-18348   [005] ...1.   545.568275: dma_buf_export: exp_name=qcom,system name=(null) size=217088 ino=2750
>>>    binder:3031_4-18348   [005] ...1.   545.568284: dma_buf_fd: exp_name=qcom,system name=(null) size=217088 ino=2750 fd=8
>>>    binder:3031_4-18348   [005] ...1.   545.568399: dma_buf_mmap_internal: exp_name=qcom,system name=qcom,system size=28672 ino=2751
>>>      kworker/5:1-130     [005] ...1.   545.570193: dma_buf_put: exp_name=qcom,system name=ab size=28672 ino=2751
>>>     RenderThread-18891   [005] ...1.   545.602994: dma_buf_get: exp_name=qcom,system name=ab size=217088 ino=2750 fd=1087
>>>     RenderThread-9409    [000] .n.1.   545.745004: dma_buf_dynamic_attach: exp_name=qcom,system name=ab size=217088 ino=2750 is_dynamic=0 dev_name=kgsl-3d0
>>>     RenderThread-9409    [005] ...1.   545.747802: dma_buf_detach: exp_name=qcom,system name=bq size=12771328 ino=2764 is_dynamic=0 dev_name=kgsl-3d0
>>>
>>> Signed-off-by: Xiang Gao <gaoxiang17@xiaomi.com>
>>> ---
>>>  drivers/dma-buf/dma-buf.c      |  48 +++++++++-
>>>  include/trace/events/dma_buf.h | 160 +++++++++++++++++++++++++++++++++
>>>  2 files changed, 207 insertions(+), 1 deletion(-)
>>>  create mode 100644 include/trace/events/dma_buf.h
>>>
>>> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
>>> index 2bcf9ceca997..6e04e12f149e 100644
>>> --- a/drivers/dma-buf/dma-buf.c
>>> +++ b/drivers/dma-buf/dma-buf.c
>>> @@ -35,6 +35,9 @@
>>>
>>>  #include "dma-buf-sysfs-stats.h"
>>>
>>> +#define CREATE_TRACE_POINTS
>>> +#include <trace/events/dma_buf.h>
>>> +
>>>  static inline int is_dma_buf_file(struct file *);
>>>
>>>  static DEFINE_MUTEX(dmabuf_list_mutex);
>>> @@ -220,6 +223,11 @@ static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
>>>             dmabuf->size >> PAGE_SHIFT)
>>>                 return -EINVAL;
>>>
>>> +       if (trace_dma_buf_mmap_internal_enabled()) {
>>> +               guard(spinlock)(&dmabuf->name_lock);
>>> +               trace_dma_buf_mmap_internal(dmabuf);
>>> +       }
>>> +
>>>         return dmabuf->ops->mmap(dmabuf, vma);
>>>  }
>>>
>>> @@ -745,6 +753,11 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
>>>
>>>         __dma_buf_list_add(dmabuf);
>>>
>>> +       if (trace_dma_buf_export_enabled()) {
>>> +               guard(spinlock)(&dmabuf->name_lock);
>>> +               trace_dma_buf_export(dmabuf);
>>> +       }
>>> +
>>
>> perhaps a macro similar to the one below
>>
>> #define DMA_BUF_TRACE(FUNC, ...)                  \
>>     do {                                          \
>>         if (FUNC##_enabled()) {                   \
>>             guard(spinlock)(&dmabuf->name_lock); \
>>             FUNC(__VA_ARGS__);                    \
>>         }                                         \
>>     } while (0)
>>
>>
>> This would help us avoid duplicating a lot of code.
>>
>> could be:
>> DMA_BUF_TRACE(trace_dma_buf_put, dmabuf);
>> DMA_BUF_TRACE(trace_dma_buf_attach, dmabuf, dev);
>>
>> ?
> 
> Thinking more about it I was wondering if we really need the userspace assigned name in the tracepoint in the first place.
> 
> The ino should be sufficient to uniquely identify each dma-buf, tracing the name should only be printed if it's changing or otherwise we spam the tracelog quite a bit with it.
> 
> BTW We don't have any identification for an attachment, so when multiple devices attach to the same DMA-buf the trace would be quite meaningless. We should probably fix that.
> 
> Regards,
> Christian.
>