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Message-ID: <20181106170736.GB27851@jcrouse-lnx.qualcomm.com>
Date: Tue, 6 Nov 2018 10:07:36 -0700
From: Jordan Crouse <jcrouse@...eaurora.org>
To: Sharat Masetty <smasetty@...eaurora.org>
Cc: freedreno@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
linux-arm-msm@...r.kernel.org, chris@...is-wilson.co.uk,
robdclark@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] drm/msm: Optimize adreno_show_object()
On Tue, Nov 06, 2018 at 11:40:06AM +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@...eaurora.org>
> ---
> drivers/gpu/drm/msm/adreno/adreno_gpu.c | 76 ++++++++++++++++++++++++---------
> drivers/gpu/drm/msm/msm_gpu.h | 2 +
> 2 files changed, 58 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> index c93702d..e29093e 100644
> --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> @@ -475,34 +475,70 @@ 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;
>
> - /* Skip printing the object if it is empty */
> - if (datalen == 0)
> + for (i = 0; i < l; i++)
> + buf_itr += ascii85_encode_to_buf(src[i], buf + buf_itr);
If this is the only use of ascii85_encode_to_buf I don't think we need it in the
common header - the same functionality can just be built in here.
> +
> + return buf;
> +}
> +
> +/* len is expected to be in bytes */
> +static void adreno_show_object(struct drm_printer *p, void **ptr, int len,
> + bool *encoded)
> +{
> + if (!*ptr || !len)
> return;
>
> - l = ascii85_encode_len(datalen);
> + if (!*encoded) {
We wouldn't need the encoded bool if you used different pointers for the
non-encoded and encoded objects -
if (!encoded) {
encoded = adreno_gpu_ascii85_encode(raw);
kvfree(raw);
raw = NULL;
}
And then just blindly kvfree() both in the destroy function - I think that
would be a bit clearer than trying to reuse the buffer.
> + long datalen, i;
> + u32 *buf = *ptr;
> +
> + /*
> + * 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 < len >> 2; i++) {
> + if (buf[i])
> + datalen = ((i + 1) << 2);
> + }
> +
> + /*
> + * If we reach here, then the originally captured binary buffer
> + * will be replaced with the ascii85 encoded string
> + */
> + *ptr = adreno_gpu_ascii85_encode(buf, datalen);
> +
> + kvfree(buf);
> +
> + *encoded = true;
> + }
> +
> + if (!*ptr)
> + 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, *ptr);
>
> drm_puts(p, "\n");
> }
> @@ -534,8 +570,8 @@ 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].data,
> - state->ring[i].data_size);
> + adreno_show_object(p, &state->ring[i].data,
> + state->ring[i].data_size, &state->ring[i].encoded);
This implies we should make a sub struct to store the data / size / state of the
buffers so this can turn into:
adreno_show_object(&(state->ring[i].object))
We could repurpose msm_gpu_state_bo for this task - this would dovetail nicely
into the suggestion above to use individual pointers for the encoded and
non-encoded buffers.
> }
>
> if (state->bos) {
> @@ -546,8 +582,8 @@ 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].data,
> + state->bos[i].size, &state->bos[i].encoded);
And then this would turn into just 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 f82bac0..efb49bb 100644
> --- a/drivers/gpu/drm/msm/msm_gpu.h
> +++ b/drivers/gpu/drm/msm/msm_gpu.h
> @@ -187,6 +187,7 @@ struct msm_gpu_state_bo {
> u64 iova;
> size_t size;
> void *data;
> + bool encoded;
> };
>
> struct msm_gpu_state {
> @@ -201,6 +202,7 @@ struct msm_gpu_state {
> u32 wptr;
> void *data;
> int data_size;
> + bool encoded;
> } ring[MSM_GPU_MAX_RINGS];
>
> int nr_registers;
> --
> 1.9.1
>
--
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