Re: [PATCH v2 1/2] app/test: add cksum performance test

[Olivier Matz <olivier.matz@6wind.com>]

Hi Mattias,

Please see few comments below.

On Fri, Jul 08, 2022 at 02:56:07PM +0200, Mattias Rönnblom wrote:
> Add performance test for the rte_raw_cksum() function, which delegates
> the actual work to __rte_raw_cksum(), which in turn is used by other
> functions in need of Internet checksum calculation.
> 
> Signed-off-by: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
> 
> ---
> 
> v2:
>   * Added __rte_unused to unused volatile variable, to keep the Intel
>     compiler happy.
> ---
>  MAINTAINERS                |   1 +
>  app/test/meson.build       |   1 +
>  app/test/test_cksum_perf.c | 118 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 120 insertions(+)
>  create mode 100644 app/test/test_cksum_perf.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index c923712946..2a4c99e05a 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1414,6 +1414,7 @@ Network headers
>  M: Olivier Matz <olivier.matz@6wind.com>
>  F: lib/net/
>  F: app/test/test_cksum.c
> +F: app/test/test_cksum_perf.c
>  
>  Packet CRC
>  M: Jasvinder Singh <jasvinder.singh@intel.com>
> diff --git a/app/test/meson.build b/app/test/meson.build
> index 431c5bd318..191db03d1d 100644
> --- a/app/test/meson.build
> +++ b/app/test/meson.build
> @@ -18,6 +18,7 @@ test_sources = files(
>          'test_bpf.c',
>          'test_byteorder.c',
>          'test_cksum.c',
> +        'test_cksum_perf.c',
>          'test_cmdline.c',
>          'test_cmdline_cirbuf.c',
>          'test_cmdline_etheraddr.c',
> diff --git a/app/test/test_cksum_perf.c b/app/test/test_cksum_perf.c
> new file mode 100644
> index 0000000000..bff73cb3bb
> --- /dev/null
> +++ b/app/test/test_cksum_perf.c
> @@ -0,0 +1,118 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2022 Ericsson AB
> + */
> +
> +#include <stdio.h>
> +
> +#include <rte_common.h>
> +#include <rte_cycles.h>
> +#include <rte_ip.h>
> +#include <rte_malloc.h>
> +#include <rte_random.h>
> +
> +#include "test.h"
> +
> +#define NUM_BLOCKS (10)
> +#define ITERATIONS (1000000)

Parenthesis can be safely removed

> +
> +static const size_t data_sizes[] = { 20, 21, 100, 101, 1500, 1501 };
> +
> +static __rte_noinline uint16_t
> +do_rte_raw_cksum(const void *buf, size_t len)
> +{
> +	return rte_raw_cksum(buf, len);
> +}

I don't understand the need to have this wrapper, especially marked
__rte_noinline. What is the objective?

Note that when I remove the __rte_noinline, the performance is better
for size 20 and 21.

> +
> +static void
> +init_block(void *buf, size_t len)

Can buf be a (char *) instead?
It would avoid a cast below.

> +{
> +	size_t i;
> +
> +	for (i = 0; i < len; i++)
> +		((char *)buf)[i] = (uint8_t)rte_rand();
> +}
> +
> +static int
> +test_cksum_perf_size_alignment(size_t block_size, bool aligned)
> +{
> +	char *data[NUM_BLOCKS];
> +	char *blocks[NUM_BLOCKS];
> +	unsigned int i;
> +	uint64_t start;
> +	uint64_t end;
> +	/* Floating point to handle low (pseudo-)TSC frequencies */
> +	double block_latency;
> +	double byte_latency;
> +	volatile __rte_unused uint64_t sum = 0;
> +
> +	for (i = 0; i < NUM_BLOCKS; i++) {
> +		data[i] = rte_malloc(NULL, block_size + 1, 0);
> +
> +		if (data[i] == NULL) {
> +			printf("Failed to allocate memory for block\n");
> +			return TEST_FAILED;
> +		}
> +
> +		init_block(data[i], block_size + 1);
> +
> +		blocks[i] = aligned ? data[i] : data[i] + 1;
> +	}
> +
> +	start = rte_rdtsc();
> +
> +	for (i = 0; i < ITERATIONS; i++) {
> +		unsigned int j;
> +		for (j = 0; j < NUM_BLOCKS; j++)
> +			sum += do_rte_raw_cksum(blocks[j], block_size);
> +	}
> +
> +	end = rte_rdtsc();
> +
> +	block_latency = (end - start) / (double)(ITERATIONS * NUM_BLOCKS);
> +	byte_latency = block_latency / block_size;
> +
> +	printf("%-9s %10zd %19.1f %16.2f\n", aligned ? "Aligned" : "Unaligned",
> +	       block_size, block_latency, byte_latency);

When I run the test on my dev machine, I get the following results,
which are quite reproductible:

Aligned           20       10.4      0.52     (range is 0.48 - 0.52)
Unaligned         20        7.9      0.39     (range is 0.39 - 0.40)
...

If I increase the number of iterations, the first results
change significantly:

Aligned           20        8.2      0.42     (range is 0.41 - 0.42)
Unaligned         20        8.0      0.40     (always this value)

To have more precise tests with small size, would it make sense to
target a test time instead of an iteration count? Something like
this:

	#define ITERATIONS 1000000
	uint64_t iterations = 0;

	...

	do {
		for (i = 0; i < ITERATIONS; i++) {
			unsigned int j;
			for (j = 0; j < NUM_BLOCKS; j++)
				sum += do_rte_raw_cksum(blocks[j], block_size);
		}
		iterations += ITERATIONS;
		end = rte_rdtsc();
	} while ((end - start) < rte_get_tsc_hz());

	block_latency = (end - start) / (double)(iterations * NUM_BLOCKS);


After this change, the aligned and unaligned cases have the same
performance on my machine.


> +
> +	for (i = 0; i < NUM_BLOCKS; i++)
> +		rte_free(data[i]);
> +
> +	return TEST_SUCCESS;
> +}
> +
> +static int
> +test_cksum_perf_size(size_t block_size)
> +{
> +	int rc;
> +
> +	rc = test_cksum_perf_size_alignment(block_size, true);
> +	if (rc != TEST_SUCCESS)
> +		return rc;
> +
> +	rc = test_cksum_perf_size_alignment(block_size, false);
> +
> +	return rc;
> +}
> +
> +static int
> +test_cksum_perf(void)
> +{
> +	uint16_t i;
> +
> +	printf("### rte_raw_cksum() performance ###\n");
> +	printf("Alignment  Block size    TSC cycles/block  TSC cycles/byte\n");
> +
> +	for (i = 0; i < RTE_DIM(data_sizes); i++) {
> +		int rc;
> +
> +		rc = test_cksum_perf_size(data_sizes[i]);
> +		if (rc != TEST_SUCCESS)
> +			return rc;
> +	}
> +
> +	return TEST_SUCCESS;
> +}
> +
> +
> +REGISTER_TEST_COMMAND(cksum_perf_autotest, test_cksum_perf);
> +

The last empty line can be removed.

> -- 
> 2.25.1
>