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

[Rob Herring]

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?

Rob