[Mesa-dev] [PATCH 4/4] gbm: Add map/unmap functions

[Eric Anholt]

Rob Herring <robh at kernel.org> writes:

> On Wed, Apr 27, 2016 at 5:01 PM, Emil Velikov <emil.l.velikov at gmail.com> wrote:
>> On 27 April 2016 at 19:51, Eric Anholt <eric at anholt.net> wrote:
>>> Rob Herring <robh at kernel.org> writes:
>>>
>>>> On Mon, Apr 25, 2016 at 7:53 PM, Eric Anholt <eric at anholt.net> wrote:
>>>>> Rob Herring <robh at kernel.org> writes:
>>>>>
>>>>>> On Fri, Apr 22, 2016 at 9:08 PM, Rob Herring <robh at kernel.org> wrote:
>>>>>>> On Fri, Apr 22, 2016 at 6:32 PM, Emil Velikov <emil.l.velikov at gmail.com> wrote:
>>>>>>>> Hi Rob,
>>>>>>>>
>>>>>>>> On 22 April 2016 at 16:50, Rob Herring <robh at kernel.org> wrote:
>>>>>>>>> This adds map and unmap functions to GBM utilizing the DRIimage extension
>>>>>>>>> mapImage/unmapImage functions or existing internal mapping for dumb
>>>>>>>>> buffers.
>>>>>>>> Ftr that this is quite sensitive and apart from the obvious breakage
>>>>>>>> (coming in a second) it will need some testing on a gnome-continuous
>>>>>>>> setup (iirc some used to hand out in #xorg-devel)
>>>>>>>>
>>>>>>>>> Unlike prior attempts, this version provides a region to map and
>>>>>>>>> usage flags for the mapping. The operation follows the same semantics as
>>>>>>>>> the gallium transfer_map() function.
>>>>>>>>>
>>>>>>>>> This was tested with GBM based gralloc on Android.
>>>>>>>>>
>>>>>>>>> This still creates a context, but I've moved it into gbm_create_device
>>>>>>>>> rather than in the map function. This should remove any need for reference
>>>>>>>>> counting and problems with memory leaks.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Rob Herring <robh at kernel.org>
>>>>>>>
>>>>>>> [...]
>>>>>>>
>>>>>>
>>>>>>>>> @@ -1004,6 +1058,10 @@ dri_device_create(int fd)
>>>>>>>>>     if (ret)
>>>>>>>>>        goto err_dri;
>>>>>>>>>
>>>>>>>>> +   if (dri->image->base.version >= 12)
>>>>>>>>> +      dri->context = dri->dri2->createNewContext(dri->screen, NULL,
>>>>>>>>> +                                                 NULL, NULL);
>>>>>>>>> +
>>>>>>>> Have you measured how much this costs us (cpu time and/or memory) ?
>>>>>>>
>>>>>>> No, will do.
>>>>>>
>>>>>> On Android (x86_64 + virgl), it is 2ms and ~2MB (out of 20). A
>>>>>> standalone test with swrast is 4ms and ~4MB. I measured with
>>>>>> getrusage().
>>>>>
>>>>> Given that existing clients of GBM don't use this API, it's not OK to
>>>>> add this cost to all of them.
>>>>
>>>> Agreed.
>>>>
>>>>> If you need pthreads to protect the allocation check at map time,
>>>>
>>>> I do...
>>>>
>>>>> there's this bit of configure.ac from libdrm so that you don't need to
>>>>> force libgbm to pull in real pthreads and its overhead:
>>>>>
>>>>> PKG_CHECK_MODULES(PTHREADSTUBS, pthread-stubs)
>>>>> AC_SUBST(PTHREADSTUBS_CFLAGS)
>>>>> AC_SUBST(PTHREADSTUBS_LIBS)
>>>>
>> Side note: pthread-stubs expands to a single .pc file on GLIBC (Linux
>> in general ?) platforms. That's because libc.so already has these
>> stubs.
>>
>>>> GBM requires DRI which already pulls in pthreads, so I don't think
>>>> this is needed. Or am I missing something?
>>>
>>> I'm fine with that, just noting that my libgbm currently doesn't link
>>> pthreads, and providing a solution if people didn't want to force
>>> linking pthreads for libgbm.so.
>> Not only yours - libgbm does not link against pthreads.so. Period.
>> The DRI modules on the other hand (amongst others) do.
>
> Okay, with Emil's patch I have it just using the stub. However, it
> seems I don't really need the above configure.ac hunk. Is that only
> needed for non-Linux/glibc builds?

Yeah, it's the tool that hides that nastiness of other platforms for
us.
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