[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <b7f72f38-2758-405b-abc7-60b73448d8bb@oss.qualcomm.com>
Date: Mon, 28 Oct 2024 11:36:15 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
Akhil P Oommen <quic_akhilpo@...cinc.com>
Cc: Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
Konrad Dybcio <konradybcio@...nel.org>,
Abhinav Kumar <quic_abhinavk@...cinc.com>,
Marijn Suijten <marijn.suijten@...ainline.org>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
Nathan Chancellor <nathan@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Bill Wendling
<morbo@...gle.com>,
Justin Stitt <justinstitt@...gle.com>, linux-arm-msm@...r.kernel.org,
dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
Arnd Bergmann <arnd@...nel.org>
Subject: Re: [PATCH] drm/msm/a6xx: Fix excessive stack usage
On 28.10.2024 11:27 AM, Dmitry Baryshkov wrote:
> On Mon, 28 Oct 2024 at 12:08, Akhil P Oommen <quic_akhilpo@...cinc.com> wrote:
>>
>> On 10/28/2024 1:56 PM, Dmitry Baryshkov wrote:
>>> On Sun, Oct 27, 2024 at 11:35:47PM +0530, Akhil P Oommen wrote:
>>>> Clang-19 and above sometimes end up with multiple copies of the large
>>>> a6xx_hfi_msg_bw_table structure on the stack. The problem is that
>>>> a6xx_hfi_send_bw_table() calls a number of device specific functions to
>>>> fill the structure, but these create another copy of the structure on
>>>> the stack which gets copied to the first.
>>>>
>>>> If the functions get inlined, that busts the warning limit:
>>>>
>>>> drivers/gpu/drm/msm/adreno/a6xx_hfi.c:631:12: error: stack frame size (1032) exceeds limit (1024) in 'a6xx_hfi_send_bw_table' [-Werror,-Wframe-larger-than]
>>>>
>>>> Fix this by kmalloc-ating struct a6xx_hfi_msg_bw_table instead of using
>>>> the stack. Also, use this opportunity to skip re-initializing this table
>>>> to optimize gpu wake up latency.
>>>>
>>>> Cc: Arnd Bergmann <arnd@...nel.org>
>>>>
>>>> Signed-off-by: Akhil P Oommen <quic_akhilpo@...cinc.com>
>>>> ---
>>>> drivers/gpu/drm/msm/adreno/a6xx_gmu.h | 1 +
>>>> drivers/gpu/drm/msm/adreno/a6xx_hfi.c | 34 ++++++++++++++++++++++------------
>>>> 2 files changed, 23 insertions(+), 12 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.h b/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
>>>> index 94b6c5cab6f4..b4a79f88ccf4 100644
>>>> --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
>>>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
>>>> @@ -99,6 +99,7 @@ struct a6xx_gmu {
>>>> struct completion pd_gate;
>>>>
>>>> struct qmp *qmp;
>>>> + struct a6xx_hfi_msg_bw_table *bw_table;
>>>> };
>>>>
>>>> static inline u32 gmu_read(struct a6xx_gmu *gmu, u32 offset)
>>>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_hfi.c b/drivers/gpu/drm/msm/adreno/a6xx_hfi.c
>>>> index cdb3f6e74d3e..55e51c81be1f 100644
>>>> --- a/drivers/gpu/drm/msm/adreno/a6xx_hfi.c
>>>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_hfi.c
>>>> @@ -630,32 +630,42 @@ static void a6xx_build_bw_table(struct a6xx_hfi_msg_bw_table *msg)
>>>>
>>>> static int a6xx_hfi_send_bw_table(struct a6xx_gmu *gmu)
>>>> {
>>>> - struct a6xx_hfi_msg_bw_table msg = { 0 };
>>>> + struct a6xx_hfi_msg_bw_table *msg;
>>>> struct a6xx_gpu *a6xx_gpu = container_of(gmu, struct a6xx_gpu, gmu);
>>>> struct adreno_gpu *adreno_gpu = &a6xx_gpu->base;
>>>>
>>>> + if (gmu->bw_table)
>>>> + goto send;
>>>> +
>>>> + msg = devm_kzalloc(gmu->dev, sizeof(*msg), GFP_KERNEL);
>>>
>>> Is it necessary after being sent? Isn't it better to just kzalloc() it
>>> and then kfree() it at the end of the function?
>>
>> Keeping it around will help to cut down unnecessary work during
>> subsequent gpu wake ups.
>
> Then, I'd say, it is better to make it a part of the a6xx_gpu struct.
I think a6xx_gmu makes more logical sense here.
FWIW, the driver allocates both _gmu and _gpu for all GPUs regardless
Konrad
Powered by blists - more mailing lists