[PATCH 4/4] drm/msm: Optimize adreno_show_object()

[Jordan Crouse]

On Tue, Nov 20, 2018 at 05:07:31PM +0530, Sharat Masetty wrote:
> When the userspace tries to read the crashstate dump, the read side
> implementation in the driver currently ascii85 encodes all the binary
> buffers and it does this each time the read system call is called.
> A userspace tool like cat typically does a page by page read and the
> number of read calls depends on the size of the data captured by the
> driver. This is certainly not desirable and does not scale well with
> large captures.
> 
> This patch encodes the buffer only once in the read path. With this there
> is an immediate >10X speed improvement in crashstate save time.
> 
> Signed-off-by: Sharat Masetty <smasetty at codeaurora.org>

Reviewed-by: Jordan Crouse <jcrouse at codeaurora.org>

I like this a lot.

> ---
> Changes from v1:
> 	Addressed comments from Jordan Crouse
> 
>  drivers/gpu/drm/msm/adreno/adreno_gpu.c | 80 ++++++++++++++++++++++++---------
>  drivers/gpu/drm/msm/msm_gpu.h           |  1 +
>  2 files changed, 60 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> index bbf8d3e..7749967 100644
> --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> @@ -441,11 +441,15 @@ void adreno_gpu_state_destroy(struct msm_gpu_state *state)
>  {
>  	int i;
> 
> -	for (i = 0; i < ARRAY_SIZE(state->ring); i++)
> +	for (i = 0; i < ARRAY_SIZE(state->ring); i++) {
>  		kvfree(state->ring[i].bo.data);
> +		kvfree(state->ring[i].bo.encoded);
> +	}
> 
> -	for (i = 0; state->bos && i < state->nr_bos; i++)
> +	for (i = 0; state->bos && i < state->nr_bos; i++) {
>  		kvfree(state->bos[i].data);
> +		kvfree(state->bos[i].encoded);
> +	}
> 
>  	kfree(state->bos);
>  	kfree(state->comm);
> @@ -472,34 +476,70 @@ int adreno_gpu_state_put(struct msm_gpu_state *state)
> 
>  #if defined(CONFIG_DEBUG_FS) || defined(CONFIG_DEV_COREDUMP)
> 
> -static void adreno_show_object(struct drm_printer *p, u32 *ptr, int len)
> +static char *adreno_gpu_ascii85_encode(u32 *src, size_t len)
>  {
> -	char out[ASCII85_BUFSZ];
> -	long l, datalen, i;
> +	void *buf;
> +	size_t buf_itr = 0;
> +	long i, l;
> 
> -	if (!ptr || !len)
> -		return;
> +	if (!len)
> +		return NULL;
> +
> +	l = ascii85_encode_len(len);
> 
>  	/*
> -	 * Only dump the non-zero part of the buffer - rarely will any data
> -	 * completely fill the entire allocated size of the buffer
> +	 * ascii85 outputs either a 5 byte string or a 1 byte string. So we
> +	 * account for the worst case of 5 bytes per dword plus the 1 for '\0'
>  	 */
> -	for (datalen = 0, i = 0; i < len >> 2; i++) {
> -		if (ptr[i])
> -			datalen = (i << 2) + 1;
> +	buf = kvmalloc((l * 5) + 1, GFP_KERNEL);
> +	if (!buf)
> +		return NULL;
> +
> +	for (i = 0; i < l; i++) {
> +		ascii85_encode(src[i], buf + buf_itr);
> +
> +		if (src[i] == 0)
> +			buf_itr += 1;
> +		else
> +			buf_itr += 5;
>  	}
> 
> -	/* Skip printing the object if it is empty */
> -	if (datalen == 0)
> +	return buf;
> +}
> +
> +static void adreno_show_object(struct drm_printer *p,
> +		struct msm_gpu_state_bo *bo)
> +{
> +	if ((!bo->data && !bo->encoded) || !bo->size)
>  		return;
> 
> -	l = ascii85_encode_len(datalen);
> +	if (!bo->encoded) {
> +		long datalen, i;
> +		u32 *buf = bo->data;
> +
> +		/*
> +		 * Only dump the non-zero part of the buffer - rarely will
> +		 * any data completely fill the entire allocated size of
> +		 * the buffer.
> +		 */
> +		for (datalen = 0, i = 0; i < (bo->size) >> 2; i++) {
> +			if (buf[i])
> +				datalen = ((i + 1) << 2);
> +		}
> +
> +		bo->encoded = adreno_gpu_ascii85_encode(buf, datalen);
> +
> +		kvfree(bo->data);
> +		bo->data = NULL;
> +
> +		if (!bo->encoded)
> +			return;
> +	}
> 
>  	drm_puts(p, "    data: !!ascii85 |\n");
>  	drm_puts(p, "     ");
> 
> -	for (i = 0; i < l; i++)
> -		drm_puts(p, ascii85_encode(ptr[i], out));
> +	drm_puts(p, bo->encoded);
> 
>  	drm_puts(p, "\n");
>  }
> @@ -531,8 +571,7 @@ void adreno_show(struct msm_gpu *gpu, struct msm_gpu_state *state,
>  		drm_printf(p, "    wptr: %d\n", state->ring[i].wptr);
>  		drm_printf(p, "    size: %d\n", MSM_GPU_RINGBUFFER_SZ);
> 
> -		adreno_show_object(p, state->ring[i].bo.data,
> -			state->ring[i].bo.size);
> +		adreno_show_object(p, &(state->ring[i].bo));
>  	}
> 
>  	if (state->bos) {
> @@ -543,8 +582,7 @@ void adreno_show(struct msm_gpu *gpu, struct msm_gpu_state *state,
>  				state->bos[i].iova);
>  			drm_printf(p, "    size: %zd\n", state->bos[i].size);
> 
> -			adreno_show_object(p, state->bos[i].data,
> -				state->bos[i].size);
> +			adreno_show_object(p, &(state->bos[i]));
>  		}
>  	}
> 
> diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
> index a3a6371..737bf45 100644
> --- a/drivers/gpu/drm/msm/msm_gpu.h
> +++ b/drivers/gpu/drm/msm/msm_gpu.h
> @@ -191,6 +191,7 @@ struct msm_gpu_state_bo {
>  	u64 iova;
>  	size_t size;
>  	void *data;
> +	char *encoded;
>  };
> 
>  struct msm_gpu_state {
> --
> 1.9.1
> 

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