Am Donnerstag, dem 15.06.2023 um 12:09 +0800 schrieb Sui Jingfeng: > Hi, > > On 2023/6/7 20:59, Lucas Stach wrote: > > Currently the FE is spinning way too fast when polling for new work in > 'way' -> 'away' > > the FE idleloop. > 'idleloop' -> 'idle loop' > > As each poll fetches 16 bytes from memory, a GPU running > > at 1GHz with the current setting of 200 wait cycle between fetches causes > > 80 MB/s of memory traffic just to check for new work when the GPU is > > otherwise idle, which is more FE traffic than in some GPU loaded cases. > > > > Significantly increase the number of wait cycles to slow down the poll > > interval to ~30µs, limiting the FE idle memory traffic to 512 KB/s, while > > providing a max latency which should not hurt most use-cases. The FE WAIT > > command seems to have some unknown discrete steps in the wait cycles > add a comma here. > > so > > we may over/undershoot the target a bit, but that should be harmless. > overshoot or undershoot > > Signed-off-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx> > > Reviewed-by: Christian Gmeiner <cgmeiner@xxxxxxxxxx> > > --- > > drivers/gpu/drm/etnaviv/etnaviv_buffer.c | 11 ++++++----- > > drivers/gpu/drm/etnaviv/etnaviv_gpu.c | 7 +++++++ > > drivers/gpu/drm/etnaviv/etnaviv_gpu.h | 1 + > > 3 files changed, 14 insertions(+), 5 deletions(-) > > > > diff --git a/drivers/gpu/drm/etnaviv/etnaviv_buffer.c b/drivers/gpu/drm/etnaviv/etnaviv_buffer.c > > index cf741c5c82d2..384df1659be6 100644 > > --- a/drivers/gpu/drm/etnaviv/etnaviv_buffer.c > > +++ b/drivers/gpu/drm/etnaviv/etnaviv_buffer.c > > @@ -53,11 +53,12 @@ static inline void CMD_END(struct etnaviv_cmdbuf *buffer) > > OUT(buffer, VIV_FE_END_HEADER_OP_END); > > } > > > > -static inline void CMD_WAIT(struct etnaviv_cmdbuf *buffer) > > +static inline void CMD_WAIT(struct etnaviv_cmdbuf *buffer, > > + unsigned int waitcycles) > > { > > buffer->user_size = ALIGN(buffer->user_size, 8); > > > > - OUT(buffer, VIV_FE_WAIT_HEADER_OP_WAIT | 200); > > + OUT(buffer, VIV_FE_WAIT_HEADER_OP_WAIT | waitcycles); > > } > > > > static inline void CMD_LINK(struct etnaviv_cmdbuf *buffer, > > @@ -168,7 +169,7 @@ u16 etnaviv_buffer_init(struct etnaviv_gpu *gpu) > > /* initialize buffer */ > > buffer->user_size = 0; > > > > - CMD_WAIT(buffer); > > + CMD_WAIT(buffer, gpu->fe_waitcycles); > > CMD_LINK(buffer, 2, > > etnaviv_cmdbuf_get_va(buffer, &gpu->mmu_context->cmdbuf_mapping) > > + buffer->user_size - 4); > > @@ -320,7 +321,7 @@ void etnaviv_sync_point_queue(struct etnaviv_gpu *gpu, unsigned int event) > > CMD_END(buffer); > > > > /* Append waitlink */ > > - CMD_WAIT(buffer); > > + CMD_WAIT(buffer, gpu->fe_waitcycles); > > CMD_LINK(buffer, 2, > > etnaviv_cmdbuf_get_va(buffer, &gpu->mmu_context->cmdbuf_mapping) > > + buffer->user_size - 4); > > @@ -503,7 +504,7 @@ void etnaviv_buffer_queue(struct etnaviv_gpu *gpu, u32 exec_state, > > > > CMD_LOAD_STATE(buffer, VIVS_GL_EVENT, VIVS_GL_EVENT_EVENT_ID(event) | > > VIVS_GL_EVENT_FROM_PE); > > - CMD_WAIT(buffer); > > + CMD_WAIT(buffer, gpu->fe_waitcycles); > > CMD_LINK(buffer, 2, > > etnaviv_cmdbuf_get_va(buffer, &gpu->mmu_context->cmdbuf_mapping) > > + buffer->user_size - 4); > > diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c > > index 41aab1aa330b..8c20dff32240 100644 > > --- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c > > +++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c > > @@ -493,6 +493,13 @@ static void etnaviv_gpu_update_clock(struct etnaviv_gpu *gpu) > > clock |= VIVS_HI_CLOCK_CONTROL_FSCALE_VAL(fscale); > > etnaviv_gpu_load_clock(gpu, clock); > > } > > + > > + /* > > + * Choose number of wait cycles to target a ~30us (1/32768) max latency > > + * until new work is picked up by the FE when it polls in the idle loop. > > + */ > > + gpu->fe_waitcycles = min(gpu->base_rate_core >> (15 - gpu->freq_scale), > > + 0xffffUL); > > This patch is NOT effective on our hardware GC1000 v5037 (ls7a1000 + > ls3a5000). > > As the gpu->base_rate_core is 0, so, in the end gpu->fe_waitcycles is > also zero. > Uh, that's a problem, as the patch will then have the opposite effect on your platform by speeding up the idle loop. Thanks for catching this! I'll improve the patch to keep a reasonable amount of wait cycles in this case. Regards, Lucas > But after apply this path, the glmark2 still run happily, no influence. So > > > Tested-by: Sui Jingfeng <suijingfeng@xxxxxxxxxxx> > > > } > > > > static int etnaviv_hw_reset(struct etnaviv_gpu *gpu) > > diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.h b/drivers/gpu/drm/etnaviv/etnaviv_gpu.h > > index 98c6f9c320fc..e1e1de59c38d 100644 > > --- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.h > > +++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.h > > @@ -150,6 +150,7 @@ struct etnaviv_gpu { > > struct clk *clk_shader; > > > > unsigned int freq_scale; > > + unsigned int fe_waitcycles; > > unsigned long base_rate_core; > > unsigned long base_rate_shader; > > }; >