Linux/AM5726: USB driver performance issue

/* bulk read from g_zero */
/* apt-get install libusb-1.0-0-dev */
/* gcc -o bulkperf_x86 bulkperf.c `pkg-config libusb-1.0 --libs --cflags` -lpthread -lrt */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <getopt.h>
#include <libusb.h>
#include <sys/time.h>
#include <sys/resource.h>

static int do_exit = 0;

static void sighandler(int signum)
{
	do_exit = 1;
}

struct param {
	int		vid;
	int		pid;
	int		dir_w;
	unsigned long	n_loops;
	int		pktsz;
	int		timeout;  /* in ms */
	libusb_device_handle *h;
	char	       *buf;
} DEFAULT_PARAM = {
	.vid = 0x0525,
	.pid = 0xa4a0,
	.dir_w = 0,
	.n_loops = 3,
	.pktsz = 16384,
	.timeout = 3000,
	.h = NULL,
	.buf = NULL,
};

int main(int argc, char *argv[])
{
	struct sigaction sigact;
	libusb_context *ctx = NULL;
	libusb_device_handle *dev_handle;
	unsigned long loop = 0;
	ssize_t i;
	int r;
	struct param _p = DEFAULT_PARAM;
	int actual;
	int ep;

	if ((_p.buf = malloc(_p.pktsz)) == NULL) {
		printf("mem alloc failed\n");
		return 3;
	}
	memset(_p.buf, '\0', _p.pktsz);

	r = libusb_init(&ctx);
	if (r < 0) {
		printf("Error: libusb_init() failed\n");
		free(_p.buf);
		return 1;
	}

	libusb_set_debug(ctx, 3);

	dev_handle = libusb_open_device_with_vid_pid(ctx, _p.vid, _p.pid);
	if (dev_handle == NULL) {
		printf("Cannot open device\n");
		goto out1;
	}
	_p.h = dev_handle;

	printf("Device Opened\n");

	if (libusb_kernel_driver_active(dev_handle, 0) == 1) {
		printf("Kernel Driver Active\n");
		if (libusb_detach_kernel_driver(dev_handle, 0))
			goto out2;
		printf("Kernel Driver Detached!\n");
	}

	r = libusb_claim_interface(dev_handle, 0);
	if (r < 0) {
		printf("Cannot Claim Interface\n");
		goto out2;
	}

	sigact.sa_handler = sighandler;
	sigemptyset(&sigact.sa_mask);
	sigact.sa_flags = 0;
	sigaction(SIGINT, &sigact, NULL);
	sigaction(SIGTERM, &sigact, NULL);
	sigaction(SIGQUIT, &sigact, NULL);

	printf("Claimed Interface; Start transfer...\n");

	ep = _p.dir_w ? (1 | LIBUSB_ENDPOINT_OUT) : (1 | LIBUSB_ENDPOINT_IN);
	while (!do_exit && loop < _p.n_loops) {
		r = libusb_bulk_transfer(dev_handle, ep, _p.buf,
				_p.pktsz, &actual, _p.timeout);

		if (r) {
			printf("loop %ld: %s failed [%d]\n", loop,
					_p.dir_w ? "Write" : "Read", r);
			do_exit = 1;
			continue;
		}

		loop++;
	}

	r = libusb_release_interface(dev_handle, 0);
	if (r)
		printf("Cannot Release Interface\n");
out2:
	libusb_close(dev_handle);
out1:
	libusb_exit(ctx);
	free(_p.buf);
	return 0;
}